Lithium-ion 36 Vdc battery analysis and repair - Page 1
Forum section: electronics / repair

author: Tantratron
author_rank: Frequent Contributor
timestamp: June 01, 2025, 10:38:25 am
content: Hello, I've installed back in 2016 an eBike assistance kit for my wife's bicycle which cumulates more than 18.000 km.For a few months, she noticed need to recharge more often then would have suddenly no more power on the LCD controller. After doing different tests and deconstructing partially the battery, I notice the problem might be related too one 5p bus bar (5 cells in parallel), for instance row #4 (see attached pictures and RED arrow). I've tried to simply reverse engineer the 10s x 5p celles arrangement versus the BMS, see attached 2 pages with my hand sketch schematics and measurement values.I'm almost convinced the problem is related to one of few cells in the 4th bar from the left. When the eBike does not work (no energy at all), this bus bar reads around 3 Vdc whereas the 9 remaining bus bar read 3.6 Vdc so it seems like the BMS sees a low voltage threat then blocks everything. To describe simply the high level failure, once the BMS sees around 36 Vdc from the battery, it refuses to provide any energy to the LCD controller.When I connect the 36 Vdc charger, most parallel bus bar will reach 4.0 Vdc instead of 4.2 Vdc which is normal, the battery matrix has more than 9 years of everyday work. In the past, when fully charged, it was 42 Vdc (10 bars each 4.2 Vdc in serie), now we reach 40 Vdc which is not bad.My conclusion but i'm no expert on battery, the failure occurs when bar #4 gets discharged more quickly then BMS shuts off everything after global voltage check and vote. If this hypothesis is correct, do you know a specific test or isolation test to check the 5 Lithium batteries soldered in parallel as shown in the attached pictures ?More generally, what do you think of the symptoms, what do you recommend ?If say changing 5 cells (model NCR 18650PF MH12210) by new ones, is there need of special de-soldering then soldering tool, how about the BMS's re-balancing where i'd keep the 9*5 = 45 other cells ?Thank you in advance, Albert

author: ME
author_rank: Frequent Contributor
timestamp: June 01, 2025, 03:13:02 pm
content: The bms is doing its job cutting power as one group reached the low cuttoff voltage , Replace the bad cells , Dont solder them use nickel strips and a battery tab spot welder only.

author: Tantratron
author_rank: Frequent Contributor
timestamp: June 01, 2025, 04:38:39 pm
content: Thanks@MEso I guess next step is to remove the group #4 hosting 5 individual cells locked up all together (nickel strip and black hard plastic housing) as shown in my closeup pcitures attached.What simple and safe method do you recomment first to (1) remove the spot welded strip (top and bottom) from the 5 cells then (2) to remove each 5 cells through the hollow black housing matrix of this group without deconstructing all the 10x5 assembly ?

author: ME
author_rank: Frequent Contributor
timestamp: June 01, 2025, 06:38:55 pm
content: cut the nickel with sharp cutters then make sure you have 45 gallons of watter to hand then use your head.the cell holders mostly have a bit of plastic to cut at the end of the battery holder tubes so the cell can be slid out when all nickel is removed,good luck with it and fingers and toes crossed it dont go nuclear.

author: ME
author_rank: Frequent Contributor
timestamp: June 01, 2025, 07:23:13 pm
content: cut the corners of the bits at red arrows using fine cutters then push out the cells, see pic

author: ME
author_rank: Frequent Contributor
timestamp: June 01, 2025, 07:24:45 pm
content: look at top left of pic,my paint skills lack! lol

author: Tantratron
author_rank: Frequent Contributor
timestamp: June 02, 2025, 04:43:43 am
content: Quote from: ME on June 01, 2025, 06:38:55 pmSo there is no way to make a clean di-assembly or de-solder each cell initially spot welded from the metal strip linking 5 cells to re-use the same metal strip ?If I cut the strip, in fact I'll have to disable lot more cells because the fault group is #4 so that zoning involves a 2x5 strip top and 2x5 strip bottom, this might represent lot of work and new parts. Isn't a method to de-weld the 5 cells and re-sue later the metal strip ?Another question more electric, initially this battery pack was able to provide once fully charged total of 42 Vdc but now 40 Vdc. The pack has been working since october 2016, the eBike has made almost 19.000 km with approximatively 400 re-charging cycle. Can we guess the health of the 45 other cells, max charge 4.0 Vdc instead of new 4.2 Vdc to estimate their health and worth of global re-conditionning ?

author: Tantratron
author_rank: Frequent Contributor
timestamp: June 02, 2025, 05:43:34 am
content: P.S. Here is a partial update where I've been able with some sharp knife and tilting or alternating local movemebt to progressivelly de-spot-weld the 5 cells on the top side without destroying too much the nickel plate. Quick DMM measurement of each cell shows 3 of them seem OK around 3 Vdc and 2 of them almost 0 Vdc, see attached picture where I've marked with BLACK cross the failed ones.

author: Tantratron
author_rank: Frequent Contributor
timestamp: June 02, 2025, 06:47:17 am
content: Quote from: ME on June 01, 2025, 07:23:13 pmOK now success in patiently and safely de-welding the other side of group bus bar, next stept being to cut plastic holder as you mentioned

author: Tantratron
author_rank: Frequent Contributor
timestamp: June 02, 2025, 02:20:01 pm
content: It was not easy cutting each 4 corners to extract the 5 cells but I've finally made it after patience and care. Not sure if it makes sense but it was easier to extract from negative pole where I intially tried without success from the positive pole.Where do you recommend buying 5 cells (ideally same lot) to match the individual cells (see attachement) ?How about purchasing the spot welder not too expensive but still quality, what model or where to buy ?Thank you for any wisdom suggestions and guidance.

author: tunk
author_rank: Super Contributor
timestamp: June 02, 2025, 02:34:16 pm
content: Maybe this:https://www.nkon.nl/en/panasonic-ncr18650pf-3-7v-2900mah-jp.htmlHaven't used this company, but I seem to remember that they're OK.Also remember that the old cells may/will have lost some capacity,but this should be ok: The old cells may/will reach 3V sooner thanthe new cells.

author: ME
author_rank: Frequent Contributor
timestamp: June 03, 2025, 07:04:44 am
content: I brought a welder from ebay marked maple leaf , the fets all shorted on its first use ! , i then did a mod i found on yt that involved adding a cap+diode to stop the gate drive sagging and its now ok,cost about £20 if i recall.

author: Tantratron
author_rank: Frequent Contributor
timestamp: June 03, 2025, 07:42:10 am
content: Quote from: tunk on June 02, 2025, 02:34:16 pmThanks@tunk,I've looked their description, these cells were made in 2020 but I assume they're new except depleted to 0 Vdc, what do you think ?Technically my battery pack purchased back in october 2016 (see picture) when it was fully assembled including foam and blue heat shrink has roughly size 23 cm x 12 cm x 8 cmQuestion 1: total cells are 5 x 10 = 50 cells with time stamp code 6614 on each NCR18650PF which I assume 14th june 2016. So if I buy 5 cells new (never used) made in 2020, maybe it will kind of balance aging factor once installed with 45 remaing cells... am I wrong or right ?Question 2: what procedure to balance voltage or charging level when I'll assemble and solder in parallel the 5 cells then reconnect in serie with the other 9 bus bars... is it tricky to say assemble in parallel when say each volatge would be different ?Thanks for any guidance since all this charging battery pack repair or design is totally new topic for me

author: Tantratron
author_rank: Frequent Contributor
timestamp: June 11, 2025, 02:31:45 pm
content: Just a quick update, I've still not received 10 cells from Netherlands (NKON) where I need only 5 to recondition or rebuild one parallel bus of my wife's eBike battery pack. But good news, my retired neighbour who is involved into repair cafe shop in my city has lended me their unit, see attached picture but no idea of the brand.I'll first try to do some practice before engaging in the real repair once my 2020 cells arrive probably later this week.

author: Tantratron
author_rank: Frequent Contributor
timestamp: June 13, 2025, 01:28:46 pm
content: Quote from: tunk on June 02, 2025, 02:34:16 pmJust an up update, after 9 days following my order the company NKON explains me the shipment from Netherlands to France will take 3 to 4 weeks whereas their website and confirmation mail committed to 5 business days...

author: Tantratron
author_rank: Frequent Contributor
timestamp: June 17, 2025, 06:28:39 pm
content: I've finally received yesterday the 10 cells 18650 from NKON (almost 2 weeks delivery time) then I thought to check visually all the eBike battery pack. It was manufactured in France by a small company back in 2016, 3 years later part of it was partially broken including few cells un-soldered so the company charged me extra to repair.So far so good but now I'm seeing what they did which is not so good, one cell is now leaking and its black plastic spacer zoning is partially broken. They never changed or repaired these spacer so my plan is to really do it right. For the momen I've desoldered then 2nd row of 5 parallel cells, the one leaking being recycled at junkyard of my city then I really see more the project. Please see attached some pictures where I have additional questions (technic and where to buy).Question 1: the nickel welding strip which contained the 5 cells reconditioned back in 2019 has much more welding spot (they kept it and welded more) so do you think best to buy new nickel welding stripQuestion 2: they left broken 2 spacers, do you recommend to replace them or is it OK having in mind these cells could move a bit up and down now since they have been removedQuestion 3: it seems they assembled spacer model hosting groups of 3 cells so the global pattern to host 50 cells (10x5) seems irregular, is it normal practiceWhere would you buy with quick delivery spacer and nickel strip in France or in Europe ?Thanks for any guidance, recommendation and suggestions

author: Tantratron
author_rank: Frequent Contributor
timestamp: June 23, 2025, 05:39:24 pm
content: I've made a video which looks for additional advice because the more I deconstruct the battery, the more technical questions come to surface, maybe you can advise... thank youQuestion 1: how to redo or re-generate the small plastic spacer's tabs holding each cell so the cells will not move up and downQuestion 2: what soldering method to link electrically each cell with Nickel strip when spacer are modified with no more blocking tabQuestion 3: what safe and efficient method to grind the left over of previous spot welding when keeping a healthy cell before soldering to new nickel strip barQuestion 4: is it stronger and better to solder with tin instead of spot welding when replacing some cells while not fully deconstructing the top and bottom matrixQuestion 5: good link to video tutorial showing a valid and safe method to replace few bad cells inside spacer and nickel strip matrix (i.e. 10s5p topology)

author: Tantratron
author_rank: Frequent Contributor
timestamp: July 26, 2025, 07:39:10 am
content: Quote from: Tantratron on June 11, 2025, 02:31:45 pmHere is an update where I've finally got the missing parts (spacer, nickel strip, cells) then replaced 2 bus bar (each 5 cells). Unfortunately the spot welder from my neighbour would not be enough powerful even though it was 1 year and half old, it could never weld 0.15mm any nickel strip. So i've decided to rather purchase my own spot welder, this time it did a perfect job in no time choosing 80A and around 1s duration shot, see attached model picture.

author: ME
author_rank: Frequent Contributor
timestamp: July 28, 2025, 09:27:57 pm
content: Have you any links to buy the welder?.

author: Tantratron
author_rank: Frequent Contributor
timestamp: July 29, 2025, 05:17:27 am
content: I've bought it from AliExpress (paid 68 € including shipment), there are differentsellerswith different prices and rating.

author: Tantratron
author_rank: Frequent Contributor
timestamp: August 05, 2025, 08:24:21 am
content: Does anybody knows if the metal specific power connector between front panel and the cable is normalized, standardized (first picture) ?When turning and blocking clockwise the connection, should it be tight or partially loose having in mind there will be high intensity current pulse ?Regarding the spot welder tips which can be screwed, same question regarding their standardization, parts replacement, what shape for the tip ?

author: BILLPOD
author_rank: Frequent Contributor
timestamp: August 05, 2025, 02:00:11 pm
content: Good Morning Tantratron, Like ME, I too am interested in your spot welder. Concerning the cable connection, I doubt it would need to be loose, as the current can arc there and cause damage, but I don't recognize the connector. I like that it has replaceable tips, but are more available for purchase, along with other 'consumables'? I'm also curious as to how well it operates, so if you could elaborate on that, it would be very much appreciated. Thank you for your time.

author: Kean
author_rank: Unknown
timestamp: August 05, 2025, 02:17:27 pm
content: Quote from: Tantratron on August 05, 2025, 08:24:21 amIf you search for the part number on the connector you will find many matches for welding equipment parts: DKJ10-25* I've not used these connectors myself... yet...Edit to add: Apparently these are called Dinse twist-lock style cable connectors.https://dinse-us.com/wp-content/uploads/sites/2/2014/07/DINSE_Plugs_Sockets_US.pdfThe 10-25 nomenclature refers to 10-25mm2wire, and there are larger versions for up to 35mm2or 70mm2.The ones I found on AliExpress and eBay look cheap and are probably low tolerance, which could explain a loose connection. Also I saw there seems to be European and Asian versions at least for the larger sizes, which seem to have different pin lengths.

author: Tantratron
author_rank: Frequent Contributor
timestamp: August 05, 2025, 04:54:31 pm
content: Quote from: Kean on August 05, 2025, 02:17:27 pmMany thanks for finding the proper reference of these specific plug connector (high amperage pulsing). I really do not know about this specific technology but I noticed the right cable is not locking strongly as the left one. I was able to solder many times the replaced 18650 cells but I needed to pay attention how I hold one cable or it would untwist (unlock) itself.Attached a close view of this specific connector (male part) where I still do not know if it is possible to force or strengthen its mating connection with its female counterpart. I wonder that maybe using a torque tool then slighty forcing or re-gauging or grinding would solve the problem. Visually these connectors and the way they are isolated by plastic grips seems quite good but maybe this is visual. The real question about these twisting-lock connectors, what are their mechanical specification, what twist clock or counter-clock force are they supposed to guaranty versus the risk of high current discharge arcing or self-soldering.Indeed the black plastic holder embracing the male connector has written DKJ10-25

author: Tantratron
author_rank: Frequent Contributor
timestamp: August 05, 2025, 05:45:31 pm
content: Quote from: BILLPOD on August 05, 2025, 02:00:11 pmHello BILLPOD, it is not so easy for me to answer your questions because all these test are new to me.First comment about the spot welder lent by my neighbor, seeherethenhere. This unit seems totally similar, same name, parts as both amazon linksamazon 1oramazon 2where the brand is 3GOA. This model has its own batteries, maybe when new it works fine but my friend bought it 1 year and half ago, it did the job a few times but when applied to my eBike battery, it did not provide enough power, no spark, just some faint trace on 0.15 mm nickel strip.My thought was to go away from any battery spot welder: your repair an external battery pack but later, your own pack needs repair if bad internal battery or low quality which is programmed obsolescence. Hence my move towards AC-grid spot welder which seems to have different technology (i.e. super-capacitor) but I preferred on my learning curve to go simple with coil spot-welder. Now to be honest, I have not been lucky with this specific AliExpress vendor because the spot welder back case got big shocks (see pictures) and again the twist-lock partially strong of one cable (see other posts). The vendor kind of refused to send another one in exchange of this one being returned, his negotiation was very brutal and hypocritical so maybe I'll ask to Aliexpress the 90 days warranty return and reimburse. I've not decided yet but by some luck, it was doing great job to spot weld my wife's eBike battery pack repair. It was strong, I suspect it could be even very too strong so I was careful but all went fine where I was reconditioning 10 cells among 50 cells in the pack.This model seems simple, its control laws (time and amperage) button are very basic, not sure they are precise or if after doing many spot weldering in a row it will overheat or change its pulsing value or intensity. I cannot really tell because I'm quite new on all of this spot welder process but it did the job in no time. I do heat soldering for decades on electronic boards but this spot welding is really different style, it was very easy for me and the results was solid.My gut feeling, it seems powerful, reliable even though its huge shock at the back (the AliExpress vendor put it inside a clean carton so this was not shipment schock) plus the right cable not firmly twist-locked.Hoping this helps you a bit but the first model with batteries, forget it in my opinion so best buy bit more then have enough power under the pedal.

author: Tantratron
author_rank: Frequent Contributor
timestamp: August 06, 2025, 07:18:28 am
content: P.S. Regarding the spot welder which can be bought on AliExpress at different prices, maybe different qualities where I suspect vendors (traders) buy either good lots or partially quality failed stock. When looking at the external front plate, the look (black, the specific connector), I think there is an original chinese manufacturer or designer with different variations. Maybe this can tell some information, I'm attaching picture of what was printed in the carton box with reference of companies, distrobutor, model number, mails and phones.I see at least two different models from this company (black box seems the same, same connectors but different being how it is powered and controlled), see attached picture: left is mine with transformer spot welder, right ultracapacitor spot welder but charged slowly it seems

author: Tantratron
author_rank: Frequent Contributor
timestamp: August 06, 2025, 05:34:56 pm
content: Quote from: Kean on August 05, 2025, 02:17:27 pmIt seems these twist-lock connector technology might be good and reliable because they are used on more powerful soldering MIG machine. So the question is more about tolerance of the male-female matching where these are chinese copies of original DENSEL from USA.Quote from: BILLPOD on August 05, 2025, 02:00:11 pmOne thing which I've appreciated and easier to use, the external pedal to trigger the shot versus the previous spot welder where you choose digitally the time delay so you press, wait and never sure.Indeed it would interesting to have the reference of the spot welding points or see if other electrodes form factor could be inserted at both ends of each cable.

author: Tantratron
author_rank: Frequent Contributor
timestamp: August 07, 2025, 01:56:52 pm
content: I've made this second video to provide a final status on the repair or reconditionning of this eBike's 36 Vdc - 14.5 Ah battery pack. So far so good, the battery has been fully charged then eBike run tested few different times, all seems all right with no more BMS cutting off the power at 36 Vdc.I was bit worried because during first charge, the 2 replaced rows with 2020 batteries would only reach 3.75 Vdc instead say 4 Vdc or if new 4.2 V whereas other rows would all reach 4 Vdc even though made in 2016 and used during more than 8 years (18.000 km). So in the video, I still have a technical topic about the pre-charging voltage procedure of each battery cells prior the final soldering and matrix assembling, maybe some of the community can provide wisdom guidance.

author: Kean
author_rank: Unknown
timestamp: August 08, 2025, 04:00:35 am
content: I do not have any experience with an e-bike BMS, but generally a BMS can only balance at a fraction of the currents compared to full charge rate. Compared to the safety features of the BMS (protection from over-charge, over-discharge, etc), the balancing feature is usually a secondary function there to help extend the life of the battery pack. Some cheaper BMS don't even do cell balancing, just monitoring.I typically work on smaller packs of 2S1P to 4S2P, but no matter the size of the pack I would generally begin by discharging each cell (or bank of cells) to around 30% SOC (state of charge). It is a good idea to have all cells at a similar SOC, otherwise when you are connecting them in parallel you can see high initial currents between the cells, but also once the whole pack in wired series with the BMS so that the BMS doesn't have to do too much balancing of mismatched banks.In your case I imagine it will even out over a few charge/discharge cycles, but keep an eye on it as we all know how dangerous these packs can be. If you can limit the charging rate for the first few charge cycles that would be a good idea. I think you made a good choice in using some older cells to replace the bad ones rather than brand new cells - assuming they were of similar quality and capacity.I had a mains powered cell welder but it was old and became too unreliable, so now I use a Glitter 801D which seems OK but sometimes gives me trouble. The one you got looks basic, but might be something I'd consider if I was to start building/repairing larger packs regularly. I generally prefer to leave that to others.

author: Tantratron
author_rank: Frequent Contributor
timestamp: August 08, 2025, 01:36:41 pm
content: Hi@Keanand others, regarding your Gilder 801D spot welder, maybe you could detail more what type of trouble it occasionnaly generated ?N.B. As for my spot welder which seems indeed basic but I think to keep even though the 2 issues with the Aliexpress vendor, if anybody lives around my place (Toulouse suburbs, France), they might come with some metal to be tested with maybe thicker or other geometry to see how it performs with the 2 parameters (ampere pot and time pot).Now to go back on my fear or lack of knowledge of how really pre-balance 18650 prior assembly into a SP matrix, I start to wonder if the problem might be the quality of 10 cells purchased in Netherlands. I took all my notes and voltage reading about the cells (made in 2016 which have gone approximatively 400 charge-discharge cycles after 18.000 km ride) prior repair and the 10 cells (made in 2020 and claimed never used). All the cells except the one failed reach 4.0 Vdc full charge instead of 4.2 Vdc (new), long ago I remember max full charge would read on the LCD controller 42 V which progressively drifted down to 40 Vdc which is normal as cells age. When I deconstructed partially the 2 rows or bus bar (each 5 cells in parallel aka 5P), I made on purpose to do this after the BMS would block any operation, as a reminder once total voltage reached 36 Vdc instead of max charge at 40 Volts. The faulty row #4 read 3.05 Vdc whereas all others read more or less 3.6x Vdc then when deconstructing row #4, indeed 2 cells were alone 0V (one was even slightly negative volt) and the 3 other cells read 3.16 Volts. No idea why both 0 V cells or shorted cells did not short circuit the remaing 3 cells...Later I notice after heavy cleaning the glue or whatever the french manufacturer did in 2016 that row #9 had one leaking cell, another cell shock bump but surprising fact, the row kept same voltage as healthy rows of 3.6x volts. I deconstructed the 5 cells from this bus bar and read 3.68 Vdc on each cell. Anyway my decision was to change 2x5 = 10 cells purchased at NKON in Netherlands, each cells measured 3.51 Vdc so I thought (my mistake to not check full charging and health status) that it would be OK to assembly, spot welder all in the 10S5P matrix. In other words, 8 bus bar had around 3.6x volts linked in serie with the remaining 2 bus bars of 3.51 Vdc. My idea after checking the 2020 cells, wether alone or wired in parallel, they all have more or less same voltage so no real change or heavy discharge. Same logic when doing the serie wiring, no big deal between 8 rows at 3.68 Vdc and 2 rows at 3.51 Vdc.Now here is the catch, either I made a mistake to not prior fully charge the 10 cells to verify their health or the BMS firmware cannot self-balance during one charge all voltage of each 5P bus bar or the vendor sells 2020 cells not really healthy anymore. During the first charge, I did notice all 8 bus bar would reach again 4 Volts but now the 2 re-conditionned bus-bar would reach only 3.75 Volts each (same value row #4 and row #9). My wife rode her eBike few days to test going under the 36 Vdc switching off by the BMS since one row reach 3 Volts. All worked fine this time, shewent down to 35.2 V then I recharged fully the pack hoping a voltage rebalancing would take place. I let over night the eBike then earlier, partially deconstructed the Kapton and pack to check voltages of all bus bar (see picture where I did not put thermo-retractable protection since I want to easy monitor voltages for the moment).Now the bad news, again both 2 rows with 2020 cells still read 3.75 Vdc as first time whereas all other rows read 4.00 Vdc so clearly i'm in a situation of 2 rows either never fully balanced by the BMS or the NKON vendor in netherlands is selling not so healthy cells. I think we are in the 2nd case because initially prior the reconditionning, even when 2 rows had problems with 2016 cells, they would always charge up to 4.00 Vdc so why now only 3.75 VdcOne solution eventually but no idea if this is possible or safe would be to find a 5P charger, disconnect all wires between BMS and the 10S5P array then target to fully charge individually the 2 rows to verify their health. Otherwise i'm afraid it is the eternal question to find reliable and cost effective 16850 cells, the pro and cons to replace all cells or partial ones when repairing an e-Bike pack.The positive side, I've more or less learned how to repair such 18650 battery pack, how to spot welder, my wife is happy with her bike now running longer distances without recharging instead of no power once reaching 36 Vdc total. If it turns out the 10 cells are really not so healthy (max charge 3.75 V instead of 4.2 Vdc if new), I could redo the de-spot welding and weld 10 new cells but the remaining 40 cells reach max 4 Vdc so this is quadratrure of circle or head banging decision... then where to buy in trust !Maybe my figures and conclusions or hypothesis are wrong, do not hesitate to correct and guide me.EDIT 1: suppose one 18650 cell was manufactured in 2020 and never discharged (never used) so it only went self-discharge after 5 years. It reads now 3.51 volts then what are the chances it could reach again say 4 volts or max 4.2 volts after a full recharge ?EDIT 2: if the 18650 is legit original Panasonic manufactured, does its time stamp always mentions < day of the year / year >?

author: Kean
author_rank: Unknown
timestamp: August 08, 2025, 02:33:07 pm
content: Do you have a photo of the BMS at all? Not sure if we can tell much about it from a photo, but it might help to see it.I would be concerned about the charging of the replaced cells if they were at a substantially lower state of charge than the other cells. I should have mentioned that when I get new batteries (or reconditioning older packs) I will always put each cell through at least two charge/discharge cycles to see the stated capacity. I typically just use the cheap 18650 testers powered off USB C and with tiny fans. So they can only charge and discharge at a low rate, I think some are 0.5A and some can do 1.0A. I have a bunch of these, so I can test maybe a dozen cells at once. I also have the bigger battery tester and plenty of DC power supplies and DC loads for more extensive test with data logging. As mentioned after cycle testing and before pack assembly, I also use these cheap testers to drop the SOC of all cells to below 30% (e.g. a bit under 3.6V) for a little consistency and safety.As you have already assembled the pack, I would suggest doing a normal charge, check the voltages, and then do a top-up charge just on the replaced bank to try bring it up to 4.2V (or at least match the others). I would do that top-up charge at a low rate, maybe just 0.5A or 1A. Any single cell Li-Ion/Li-Po charger will do, e.g a cheap USB charger or a RC hobby battery charger. Connect it to each side of just those cells with the pack disconnected from anything else, obviously being careful of polarity and avoiding short circuits. The lower charge rate means you can use thin wires, possibly ones with alligator clips.There is no difference between a 1P or 5P charger other than the charge rate, and charging at lower rate is fine but obviously takes a lot longer. Obviously there is a difference between 1S, 2S, etc chargers as that affects the voltage required.You shouldn't need to disconnect the BMS when doing this, but keep an eye on the pack and I suggest you never leave it alone while charging. You can stop and restart the top-up charge cycle as needed. Immediately after charging, the cells should be near 4.2V but over the next few hours they will settle down to around 4.0V or a bit below that.If you haven't seen the Battery University website, then I suggest you spend some time reading articles there. It is very a good site. What they say there will be more authoritative than anything I have said. Maybe start with this linked article, and any relevant looking ones linked from there:https://batteryuniversity.com/article/bu-910-how-to-repair-a-battery-packRegarding the Glitter 801D welder: I have only used it about 3 times since purchase, and the last time was quite a few months ago. I recall having two problems. The first was very common - getting the right settings to get a strong weld without totally evaporating the metal. This will vary with quality and thickness of your nickel strip, and also your welding probe tips and your technique. I bought it with both handheld and fixed probes, as well as the foot pedal. The second problem was that sometimes the unit just wouldn't power on. I know it takes quite some time to charge the super caps before use, but it just sometimes did not want to work... and then it would. I don't recall if I worked out the cause, but I know it was very frustrating. I believe it has several safety features including an orientation sensor, so maybe that was it. I probably wrote down some notes somewhere...Edit: Oops I forgot to mention... if those replacement cells from 2020 had been sitting for nearly 5 years without any use, then they likely have lost capacity or even gone bad. Typically you need to cycle a Li-Ion/Li-Po cell at least once a year or something like that. Again why I run at least 2 test cycles to see what capacity value I get. If the capacity changes much between the 2 tests cycles, or it is significantly different from other cells or what I expect, then I might run more or just put that cell aside. I don't know if the seller did anything like that before shipping them. In theory they should not store or ship them at a full SOC, and regulations for air shipment are less than 30% SOC.

author: Kean
author_rank: Unknown
timestamp: August 08, 2025, 03:03:47 pm
content: OK, replying to your edits that you made during my long reply (& edit).QuoteMaybe... probably... it depends on a lot of factors like brand/quality/capacity of the original cell, storage temperature, and possibly how rough or gentle you are on the cell after it sat all that time.I would say it will most likely charge to 4.2V fine unless it is dead. But the final voltage it charges to (or settles to after the charge) is not all that relevant unless it is below 3.7V (the nominal cell voltage). The relevant data is the discharge curve at whatever current you are drawing, as this is determined by the available capacity as well as the cell ESR*.If that curve is significantly different to the other cells in parallel then some cells in the bank will be put under more stress than others and likely fail early. **If the discharge curve of one bank is significantly different to the other banks in the pack, then the BMS should detect the imbalance and disconnect the pack before damage is done.* I now realise that didn't mention ESR earlier, so let me know if you already know about that or not. I mentioned above about charging and discharging during testing an 1A or less, as this is easier and gentler but slower. You don't need heavy duty equipment, wires, connectors, and the ESR does not have such a big impact on voltage or cell temperature. The voltage at a particular SOC will depend on charge/discharge rate, ESR, and temperature.** Edit to add: you can't really detect this once the cells are wired in parallel except maybe via individual cell temperatures - something very hard to measure in a densely assembled pack.QuoteSorry, I don't know but it seems likely. The labelling may also change with battery "generation". Look at some e-bike or torch related forums for description or photos of genuine vs fakes. I used to like browsinghttps://www.candlepowerforums.com/In the past I think I have mostly used Sony cells for 18650 Li-Ion, but I often buy Panasonic brand for prismatic cells. Lately I have been working more with LiFePO4 packs.

author: Kean
author_rank: Unknown
timestamp: August 08, 2025, 03:39:31 pm
content: Just pulled my Glitter 801D welder out from under the bench before I go to bed. Once I found the correct charge cable I made for it * (15V 2A with 1.3mm barrel plug), I was able to power it on with no problem. It will take 20 minutes to charge, so I am not going to leave it plugged in - but at least it powered on properly today.* The plug pack PSU it came with had a Euro style plug, no good for Australia, and I hate the cheap adapters they provide. The PSU also didn't look particularly good quality or properly certified, so I do not use it for safety reasons.

author: Tantratron
author_rank: Frequent Contributor
timestamp: August 08, 2025, 06:23:51 pm
content: Hello@Kean,First per your request, here are few pictures of the BMS which was bit hard to remove the very sticky foam installed by the french manufacturer in 2016. Part of the paper model was destroyed but he put some kapton then I removed the strong glue so we can read its P/N, namely ANN04-10S-20A but no idea of this chinese brand, schematics.Second about the 10 cells purchased from NKON in Netherlands, they are really the same model and reference as the 2016 except they claim to have been manufactured in 2020. I do read 2020 on these cells but oldest cells. I still have doubts about if they are legit from Panasonic or fake, not easy to say. One clue being the 2016 cells have printed 6614 date code which is clearly 2016 - june - 14 but I'm surprised lately why Panasonic would only printed 2020 or 2021 without day or moth or week from 2020. The other clue, as explained before with the previous bank with problems, they would charge up to 4 V so why now the replaced 2 banks reach only 3.75 V so in that case, their health status would be bad.Lastly I might give a go to your top-up charge method on the two banks but I'm still not sure to fully understand your wiring or de-wiring instructions to connect the charger, how to avoid destroying the BMS or short-circuit other banks. The 10 banks are all wired through nickel strip hence depending the schematics which I do not have any knowledge, how can we be sure it will not trigger other effects. Shall I disconnect the 11 pins connector which sense all metal strips bus bars as a safety, how about the main + and - terminal...Albert

author: Kean
author_rank: Unknown
timestamp: August 08, 2025, 07:50:38 pm
content: Yeah that date code does not match the Panasonic format like your 6614. e.g. trying at this websitehttps://batterybro.com/pages/18650-date-code-lookup-toolIt could be 20th week of 2020, but not Panasonic. What is the exact part number labelled on these new cells? Is it NCR18650xx?Also what is their C rating (capacity)? Around 3000mAh? And I presume the same capacity as the others from 2016?You mentioned a voltage display. Is that on the charger or e-bike? Or just your DMM?Some BMS have Bluetooth or other comms to show pack & balance voltages, but I don't think this one does.Your BMS is from ANN Power Technology (Shenzhen)http://www.annbattery.com/- but I couldn't get that website to work properly.I did not find that exact BMS anywhere, but I did find a listing for an ANN 7S 20A version, and yours is almost identical except for the 3 extra cells.https://vruzend.co.uk/products/7s-24v-20a-bms-li-ion-ann-battery-ebike-e-bike-balancing-uk-seller-uk-stockThe part number format is different, but you can see in the picture the same shape and the Blue, Yellow, and Black wires to P-, C-, and B- terminals.On that page is a wiring diagram that should help you understand how it is connected. Just imagine adding B8/B9/B10 and the voltage will be 36V nominal.Note the instructions regarding connections:QuoteFrom the specifications we can see "Balanced Current: 50mA". So it does do balancing, but only very slowly and possibly only when on charge.There are typically two type of balancing - active or passive. Active moves charge between neighbouring cells, but passive just slowly discharges the higher voltage cells.Not sure which is supported here, but I am guessing the simpler passive version.Lets do some math...With 5 cells in parallel of say 3000mAh, that is 15000mAh total.I will guess that at 3.75V they are 90% charged. The remaining 10% would thus be 1500mAh. Balancing at 50mA, that would take at least 30 hours.Clearly these BMS balancing circuits are not really designed for this much difference - more like just some 10-100 mV.I think what is happening is that the older cells are getting to a fully charged state quicker than the replaced cells. The charger supplies about 42V max at some amps to the cells, but as most banks of cells are fully charged there is not enough current flowing so the low voltage bank can charge fully. The balancing should help by pulling charge from the full cells, but it will only happen very very slowly. And I don't like suggesting to leave it on the normal charger for so long, unless you do it outdoors where a battery failure cannot cause too much damage or injure anyone. If that is possible then you can check the cell voltages every few hours to see if anything improves.My suggestion is to connect a single cell charger across the low voltage cells. You need to be very careful when doing this, but you do not have to disconnect the BMS (especially noting the warning above). The BMS is normally powered on anyway by the batteries and slow changes in voltages at low charge currents should be OK. You could unplug the 11-pin balancing connector and make the connection to the cell that way if you can do it safely. You must not have the pack connected to the e-bike, charger, or anything else when doing this. If those replaced cells are not in good condition, it may be possible to improve them by doing this a few times: charge, top-up, discharge (ride), etc.I can draw a diagram to help if needed, but first do you have any charger for Li-Ion/LiPo cells rated at 500-1000mA at 4.2V?

author: Tantratron
author_rank: Frequent Contributor
timestamp: August 09, 2025, 05:38:34 am
content: Quote from: Kean on August 08, 2025, 07:50:38 pmI've always read each bank's voltage using my DMM.As for cell marking, except the strange or fake manufacturing date, wether original cells (2016) or the 10 cells purchasedto NKON in Netherlands, it is only printed as model reference NCR18650PF / Li-Ion MH12210. Note the vendor now states 2021 but when I bought these last june, it was 2020. Since then, I've read that one method to estimate if fake or real is to check the weightt of each cell. At that time, i did not know all these topics so now the 10 cells are all soldered with nickel strip but the NKON vendor states 46 g but I never weighted them prior welding.It was one member in this thread who suggested this vendor and model clearly looking the same as my 2016 cells. Another friend told me some good reports about this vendor plus checling trustpilot rating, I've bought in confidence. So this leaves either the topic of 2020 cells sitting unused for 5 years or fake ones or another root cause why they do not charge up to 4.0 or 4.2 VQuote from: Kean on August 08, 2025, 07:50:38 pmLast night after deconstructing the glued foam and making pictures for you of the BMS, I did disconnect the 11 pins monitoring cable but let the 3 main power wires (i.e. B- and B+ soldered on their respective nickel strip bank) !It seems maybe this video technical report shows some information about this BMS modelQuote from: Kean on August 08, 2025, 07:50:38 pmFor the moment, I do not have any Li-Ion/LiPo charger or tester

author: Tantratron
author_rank: Frequent Contributor
timestamp: August 09, 2025, 10:29:59 am
content: Later today, I've reconnected the 11 pins voltage sensor to the BMS then re-installed the battery-pack into the e-Bike. It seems to work fine (LCD and controller works) so I guess, no harm was done with improper sequence of connectors/cables removal. Namely the battery pack alone (no load, no motor, no LCD, no charger attached to it), only B- cable, B+ cable still soldered on the end nickel strip banks, wether removing live or re-connecting the 11 pins sensor seems to be trouble free. I've updated the system synoptic, see attached picture of my notes so it seems if no load neither main charger connected to the BMS then the BMS chips only get power via the 11 pin connector (B1- ground and B10+).Quote from: Kean on August 08, 2025, 07:50:38 pmWhat i'll do later is to solder two connectors on each partially failed or not fully charged bank (bank #4 and bank #9), each connector would allow local low power charging injection so it would simplify consuming task to remove battery pack, re-install, do e-Bike running, check.Now are you really sure it is not better and safer to disconnect the 11-pins balancing connector while injecting charge through either bank #4 or bank #7 ?I ask because clearly the BMS constantly receives power via B1- and B10+ wether eBike runs or not, see again the attached schematics. If you think it is OK and safe to leave the 11-pins balancing cable, it would simplify my process because the battery pack would stay in its box. Furthermore say we leave the 11-pin cable attached to the BMS, the chip firmware might actually decide or be troubled by local injection power, volatge change then re-balance or act strange, no idea how these BMS actually works.Anyway in the mean time, I'll first solder two injection cables plus plus pins to monitor with my DMM the bank's voltage increase. However i'm open to any suggestion on what cheap or simple low power charger I could use then again, does the BMS power on while parallel local bank charging is safe and sound.Thank you again, Albert

author: Tantratron
author_rank: Frequent Contributor
timestamp: August 09, 2025, 01:25:22 pm
content: P.S.1. There is someting I do not fully understand, maybe someone has a partial schematic of this BMS.If I leave the 11-pin balancing cable connected to the BMS board, wether measuring voltage from Battery or or Power output from BMS,I do get the same value, namely 39.24 Vdc. However if I disconnect the 11-pin cable from the PCB connector, the Power output voltages drops a bit to 37.89 Vdc.In all cases, the reference is B10+ or shared positive pole of the battery. If reading battery's total voltage, it is between B10+ and B1- or B- of BMS whereas reading BMS power output, it is between B10+ and P- in the previous synposis diagram.What is the root cause of this drop of voltage of 2.35 Vdc having in mind there are 4 mosfets in this BMS ?P.S.2. I've just found this articleabout RESET a BMS, could this make sens in my scenario where maybe the firmware stores some charging curves or data ?

author: Kean
author_rank: Unknown
timestamp: August 09, 2025, 03:55:14 pm
content: Quote from: Tantratron on August 09, 2025, 10:29:59 amMy understanding of that warning is that you should not connect the 11-pin balance connector before connecting the black wire to battery negative. It is OK to unplug or plug in again after that as long as the B- wire is connected. The P- and C- shouldn't be used for operation/charging of the pack without the balance connector plugged in. The BMS should isolate the pack from P- and C- if you unplug the balance connector as it sees a fault condition. It does this isolation via the large MOSFETs under the heatsink.Quote from: Tantratron on August 09, 2025, 10:29:59 amYes, that sounds like a good idea. You can check the full pack voltage, and divide by 10 then compare with those problematic bank voltages. The wires only need to carry 1A or so, but make sure they don't get crushed/shorted and that the connector also cannot be shorted or connected in reverse. There is no protection provided by the BMS on those wires, so if i does short then the thinner wires will at least melt pretty quickly, but it will be ugly and is not good for the cells.Quote from: Tantratron on August 09, 2025, 10:29:59 amYou can unplug the balance connector if you want, but it won't really have any effect other than shutting down the BMS. The BMS is only monitoring cell voltages (and maybe temperature) and then controlling the MOSFETs that isolate P- and C- from B-. If you inject power to one bank it will just see the voltage change there and I don't think it should be troubled by it. I don't think the BMS is that smart, as its main purpose is isolation for over current, over voltage, and under voltage. For under/over voltage it should monitor each bank voltage not just the pack voltage.One thing you probably should avoid is injecting charge into more than one bank at the same time. If you have two chargers, then they might have a common negative connection (through the USB/PSU or mains earth) and that would short out any banks in between those connections which would be very bad.So if you want to disconnect the balance connector that is fine, but I really do not think it is necessary. Just do no have e-bike or charger connected at the same time.Quote from: Tantratron on August 09, 2025, 10:29:59 amI'm not sure what chargers might be available to you - but if you find one from a local electronics store/eBay/Amazon then you can ask us about it. I make many circuit boards in my factory for devices with low current charging, so I have many options - but I also have some Turnigy RC chargers from Hobby King which I use for bigger packs and they are configurable for different battery types, voltages, and currents so they are very handy to have.Another idea I had today was to get a separate active balancer that does higher current balancing and connect it instead of the BMS for a day or two. Or you could get a better BMS to replace that one. One example of an active balancer that is available for 10S and does 1.2A balancing is this:https://www.aliexpress.com/item/1005008902994380.html*** Looking again at that active balancer on AliExpress, and I don't think it has the same connector as your BMSQuote from: Tantratron on August 09, 2025, 01:25:22 pmI don't have a schematic of the BMS, but this would be the same as what that Battery Doctor video shows when he cut off the temperature sensor and shorted it to simulate a high temperature.What I believe is happening is that the BMS is detecting a fault when you unplug the balance connector and isolating the P- and C- from B-. When measuring with your DMM you will still see a voltage due to leakage current through the MOSFET, but you will not be able to charge or discharge the battery. This is similar to ghost voltages that electricians might see on house wiring, and good a DMM might have a LoZ voltage mode to remove the ghost voltage. A DMM normally has an input resistance/impedance or 10MΩ, so normally the DMM draws almost no current. In LoZ mode the resistance might drop to a something like 3kΩ which removes any leakage/ghost voltage to confirm if there is any real power source.If you don't have LoZ mode on your DMM, then you can confirm this is correct if you have a resistor to use as a load on the battery. With about 36-42V and a small resistor (0.25W) you would use a resistor value of 10kΩ which would draw about 4mA at 40V and consume 0.16W. If you place this across the DMM inputs when connecting the battery, it should confirm the MOSFETs are isolating the battery.Quote from: Tantratron on August 09, 2025, 01:25:22 pmI don't think your BMS has a reset feature, so I wouldn't recommend trying this. The Yotobike likely has a much more advanced BMS, like the ones that you can connect to with Bluetooth.

author: Tantratron
author_rank: Frequent Contributor
timestamp: August 10, 2025, 02:32:24 pm
content: Hello@Kean,I keep hesitating or mind rambling on what should I do now.First there is still this open conclusion about if these cells made in 2020 with no standard manufacturing date or the fact they stayed 5 years unused could explain the issue.Second clearly I've done a big mistake to not charge-discharge test the 10 cells prior spot welding them inside the 10S5P matrixThird I've replaced 2x5 = 10 cells among 50 cells (2016 made with 400 charge-discharge cycles) so this represents 20 % of the matrix to be re-balanced, this is maybe a lot compared say to change one cell failed among 50 cells. The technical topic or business to repair Lithium-Ion pack might be more tricky or demanding about tools, process...Fourth there is not really any information about the firmware doing the balancing in this 2016 BMS hosting 4 mosfet, maybe 2 banks with other chemical history to be balanced among 10 banks cannot be handled by the algorithm.Quote from: Kean on August 09, 2025, 03:55:14 pmI only have two DMMs, one EX655 and one EX355 but both only offer AC LoZ, no DC LoZ. So I've done as suggested, namely normal DC mode with 10 K shorting the P- with B+ which confirms what you said, the voltage was around 1.17 VdcQuote from: Kean on August 09, 2025, 03:55:14 pmOne option I might buy (please share thoughts and advices) would be to purchasethis 10x unit 1S pack. It was suggested to another forum dedicated to Advantest R3261/R3361 repair to replace the 3.6V - 150 mA NiCd battery so my idea was to use some of the 18650 cells removed from the e-Bike battery for this retrofit. The vendor sells 10x so maybe I could use one unit connected to a 5Vdc power supply to inject/charge sequentially bank #4 and bank #9.Quote from: Kean on August 09, 2025, 03:55:14 pmI might later solder 2 sets of wires then protect them from shorting in order to later charge bank #4 and bank #9 as well as check their hopefully increasing voltage. So maybe I'll let the balancing connector plug connector so I can globally check the total 10S voltage through the LCD/VFD driver of the eBike. As safety I'd unplug the tri-phase output from the VFD driver connected to the eBike motor.

author: Kean
author_rank: Unknown
timestamp: August 10, 2025, 03:15:18 pm
content: OK, I agree in general with your summary. It is a pity you didn't know enough to weigh or test the cells prior to rebuild, but I am glad to hear the DMM with resistor worked for you to confirm the correct BMS protection functionality.That device you link to is not a BMS or charger, it is just a single cell PCM. It protects the battery in a similar way to the BMS, but no balancing and definitely not smart. I know these devices well, and use them more than I use a BMS. They just have one voltage detection IC and a MOSFET and are required for use of an unprotected cell on its own usually at lower currents (e.g. 2-6A). By all means get some to protect the removed cells and use them for other projects in a safe manner, but they do not solve your charging requirement.FYI this is one type of many cell charger/testers that I have which are pretty cheap. I think I have several of both 2-cell and 4-cell version and they have worked fine.https://www.aliexpress.com/item/1005005444930813.htmlNote that these can only do discharge test at low current (max 1A) so not ideal for proper testing of your cells where you really want to do individual cell tests at 4A or more, but usually a 1A test will show obvious problems when you compare the capacity and ESR measurements against specifications or between a good and bad cell.Maybe (hopefully) someone else will provide some further recommendations of what you should do next.

author: Tantratron
author_rank: Frequent Contributor
timestamp: August 10, 2025, 06:55:37 pm
content: Quote from: Kean on August 08, 2025, 07:50:38 pmI could not get either the ANN Power Technology to work properly with Safari on MacOS then I using Chrome, it works throughthis linkwhich now works with Safari. It seems their new version added a temperature sensor, mine does not have this sensor which was reported with some issues in one YouTube video. It is supposed to to do current balancing and voltage balancing but as you said, current balancing is very slow and I guess voltage balancing only done when reaching 4.2V

author: Tantratron
author_rank: Frequent Contributor
timestamp: August 11, 2025, 05:20:46 am
content: Quote from: Kean on August 10, 2025, 03:15:18 pmI do not understand the meaning of your last sentenceBy all means get some to protect the removed cells and use them for other projects in a safe manner. Does the 1 cell PCM product on AliExpress is good or not good idea to use on my removed cells (1 cell for one project) or what technical mean do you suggest to use for protecting each of them ?Among the 10 cells removed, I have only kept 6 of them: 3 cells have 3.16 V and 3 cells gave 3.68 VTo go back on solving or living with my e-Bike battery, I plan to apply the top-up charge you mentionned few days ago but what minimal charger model or DIY technical method do you recommend to top-up one 5P bank ?

author: Kean
author_rank: Unknown
timestamp: August 11, 2025, 06:01:33 am
content: Quote from: Tantratron on August 11, 2025, 05:20:46 amAs the cells you have removed are unprotected, then if you want to use them in another project you must add some alternate protection - either a PCM or a BMS.A BMS is basically a PCM plus cell balancing and possibly some additional smart features for monitoring/communications. Here is an article (the first from a google search) that explains the differencehttps://www.danenergy.com/blog-posts/pcm-vs-bmsTypically a protected 18650 has a round PCM on the top which makes protected cells a bit longer, so can fit in a battery holder (well most of the time, some holders are too short).Something like this:https://www.aliexpress.com/item/32994144009.htmlThe long thin PCM PCB that you linked to are also common and usually covered by heatshrink after wiring up with a pigtail connection, but then cannot fit into a battery holder.There are lots of other sizes and shapes of PCM for different number of cells and current ratings, just like there is a large range of BMS products.Most of the time I build battery packs that are 1S to 4S, and used at less than 2A - so I typically use a PCM, as cell balancing is not usually a problem in the lifetime of these products. I don't usually use the 18650 cell holders in my products.If you get a cell tester like the one I linked yesterday then you can run some tests on those older spare cells to see if they are any good before you add a PCM. Make sure they can charge to 4.2V and discharge capacity is usable (typically 70% or more of spec). Also ESR should not be too high, else the cell is close to failure. You will want some thin nickel strip like 3mm wide and 0.1mm thick to weld to the cells and then solder to the PCM. You can get it on AliExpress in pre-cut lengths or rolls. Some is solid nickel, and some is nickel plated steel. Not important at lower currents.As I previously mentioned, I do not think the ANN BMS is smart. It likely does not have a microcontroller or firmware. Usually just a bunch of discrete protection/balancing ICs and MOSFETs. I could only find a left over 3S 40A BMS in my box, and it is like this with no microcontroller. It is similar to the BMS PCB shown with this producthttps://www.aliexpress.com/item/1005007606405119.htmlYou could remove the metal heatsink from your BMS to investigate further if you wanted top pull it apart again...For the topping up, I would suggest getting some cheap USB-C 1A charging PCBs. Search Amazon or AliExpress for "Lithium Battery 1A Charger PCB". These will be very handy if you use those removed cells in other projects.I don't know if you will be able to view this from France, but try these examples (just quick search results, not sellers I have used)https://www.amazon.com/HiLetgo-Lithium-Battery-Charging-Protection/dp/B0CDWZ9MDC/https://www.aliexpress.com/item/1005008963528308.htmlhttps://www.aliexpress.com/item/1005003586772730.htmlSome of these charging PCBs include a basic single cell PCM as well for hard wiring to an unprotected 18650 (the ones that mention "protect").

author: Tantratron
author_rank: Frequent Contributor
timestamp: August 11, 2025, 08:30:31 am
content: Many thanks@Keanfor your time, data, references and links so I'm going to do my homework absorbing this knowledge: 10S active balancing network board, 1P charger with protection (BMS), 1P charger no protection PCM, 2 cells or 4 cells charge/discharge tester.As I've mentioned before, my bigger mistake was to directly spot weld 2 banks (each bank 5P cells) without doing any integrity test (weight, charge/discharge health monitoring) of the 10 cells purchased at NKON in Netherlands. Ultimately one option for me would be say to de-weld say one bank (5 cells) then do these tests. For the moment, I'm not in the mood neither time to do this so I'm rather focussing on your idea to top-charge separatly each banks while they are electrically wired in a 10S5P matrix.So I'll solder separate +/- wiring to directly connect each faulty or not fully charged banks but 2 questions come now to mind.Question 1: maybe i'm wrong but suppose I directly connect one USB-C 1A charger PCB to one bank, this bank has actually 5 cells (5P wired) so isn't a risk or issue or analog/digital blockage from the charging board since the 5 cells in Parallel will try to absorb 5x current than one cell would do alone ?Question 2: if I decide to purchase 2 cells or 4 cells charge/discharge tester module, does this module could actually be used by remote wiring charge the 5P bank or its firmware, sensor only assume one cell to be charged/discharge/monitored.One synthetic question fused from Q1 and Q2: can we use a charger or tester designed to individually connect/interact only with one cell onto a bank with 5P cells ?P.S.1. i've suddenly remembered one detail about the AC-grid 36V-5A charger used since 2016 to recharge my wife's eBike. This unit has red LED and green LED so for many years, it would stay RED as long as charging was not completed (this would also make its internal fan active to blow air). Once the battery pack was considered fully charged, it would display GREEN and its internal fan stop. When my wife reported to me few months ago her eBike would suddenly stop, it took me some time finally realize one bank was partially dead so the BMS was cutting power at 36 Vdc (faulty bank reached 3 V whereas all other banks were 3.6 V). When running the main charger, it would work then always PING-PONG mode for ever like 10 s GREEN then 10 s RED display. No idea if this was in relation with the BMS managing or polling the 10 banks values however when i've replaced the 2 banks, still this same effect of ping-pong mode.Quote from: Kean on August 11, 2025, 06:01:33 amP.S.2. do you know if my actual BMS when connected to my battery pack including 11-balancing harness does a permanent slow analog self-balancing of the 10 banks ?

author: Kean
author_rank: Unknown
timestamp: August 11, 2025, 01:08:25 pm
content: Oops, my reply failed to post as the attachments were way to big... so I lost all the text. Will try again but don't have time to re-write everything.Quote from: Tantratron on August 11, 2025, 08:30:31 amA (typical) battery charger will do constant current until it approaches the max voltage and then switch to constant voltage. So the charger cannot supply more than 1A no matter what the cells can absorb. It will just take five times as long to charge the 5P bank vs a single cell. With 2900mAh cells, that is approx 3 hours for one cell from empty to full, and 15 hours for 5P. It actually takes a bit longer as the current drops as it approaches the full voltage, and also some charge is lost as heat in the battery due to ESR.Quote from: Tantratron on August 11, 2025, 08:30:31 amYes, they can be used with remote wiring, and you get real time reporting of voltage and current.The 4 channel unit I have actually has terminal blocks for easy connection to external cells. It is powered off USB-C and I think might limit to a max of 2A, so with 4 cells only 0.5A charging.On review I remember that the 2 channel unit is actually only really 1 channel as the left side battery holder is only for supplying power while doing discharge testing on the right side battery. Or you can use it with USB-C power source and no battery on left side, but still only test cells in the right side holder.Quote from: Tantratron on August 11, 2025, 08:30:31 amNo. You would have to break the welds to isolated at least one side of the cell from the bank.You can't even use thermal imaging to detect hot cells except for those around the outside.Quote from: Tantratron on August 11, 2025, 08:30:31 amThis is probably the BMS going into protection mode near "full charge" due to the cells being unbalanced, and auto resetting after some seconds. That would probably mean that leaving it on charge for many days would still not achieve a balanced pack.That is why I suggested the top-up charging of the unbalanced banks. It is possible those replacement cells are bad, but it is also possible they just need longer to charge because they have more life and thus higher capacity.Quote from: Tantratron on August 11, 2025, 08:30:31 amNo idea. I suggest to contact ANN Power and ask them for more info.I had a look around my office and I only found a 3S 40A BMS. It is very basic, and has no microcontroller but just a bunch of MOSFETs, resistors, and small cell monitoring ICs.It looks like the BMS PCB in the producthttps://www.aliexpress.com/item/1005007606405119.htmlI suspect if you removed the heatsink from your ANN BMS we will not find any microcontroller.

author: Tantratron
author_rank: Frequent Contributor
timestamp: August 12, 2025, 04:18:26 pm
content: Ok after pondering different options, routes, the high risk that either then 2020 cells are not so healthy or require more charge to reach max voltage versus the 2016 cells, I've mixed 40 cells (2016) with 10 cells (2020) so 20% replacement, many other things or explanations plus my initial mistake to not verify the 2020 cells prior spot-welding... anyway the minimal route I plan to follow now, first i've ordered10S active balancerand4 channel charger/tester.Once I will receive both boards, I'll solder or bridge permanently the 11 balancing wires onto the battery pack so two sets of permanent balancing cable: one for the BMS and another one for the external active balancer. Not sure if BMS can be live connected with an external active balancer so I'll first disconnect the BMS balancing wires before connecting the active balancer.The charger/tester will be used first to check the health from 2x3 = 6 cells (2016) removed, 3 cells from bank #4 and 3 cells from bank #9 having in mind 2x2 = 4 cells were trashed for their evident failure. Then depending on the active balancing result, I'll use the charger to top-charge individually bank #4 and bank #9 to check if they can reach higher max voltage than 3.75 V

author: Kean
author_rank: Unknown
timestamp: August 12, 2025, 04:50:03 pm
content: I've got one of those active balancers coming in the next few days, although I got the 8S version.I saw that some other listings for similar PCBs state that they are not suitable for maintenance, i.e. the kind of job you are doing - but I cannot see why exactly.Also there is mention to plug the connector on at an angle to ensure B- connects first to avoid damage.I considered one of the Heltec active balancers with display, but until I get around to making another battery pack I will put off spending the money as I'm not sure if I will build the next pack as 6S or 8S and Li-Ion or LiFePO4.https://www.aliexpress.com/item/1005009156921328.htmlWhen you get the cell tester feel free to reach out if you have questions.

author: BILLPOD
author_rank: Frequent Contributor
timestamp: August 12, 2025, 07:22:34 pm
content: Tantratron, Thank you for the information on the spot welder. VERY much appreciated.

author: Tantratron
author_rank: Frequent Contributor
timestamp: August 20, 2025, 06:17:39 pm
content: Quote from: Kean on August 12, 2025, 04:50:03 pmI've received the cell tester today and hope to receive the cell balancer in a few days.As a reminder, I've replaced 2 banks each 5P among the 10 banks from the 10S5P matrix.Bank #4 was the major problem, namely 2 cells among the 5 were totally dead (close to 0V once removed) so that bank was only running with 3 cells which might have aged significantly due to parallel stress.Bank #9 was another problem, one cell was leaking and another cell got some bumps but paradoxically, none were aged compared to the 3 lefts.Anyway I recycled in junkyard 2 cells from bank #4 and 2 cells from bank #9 so I still have 3 cells of each bank.Attached pictures showing preliminary test: no charge, no discharge, just first use of the cell charger-tester from AliExpress, left cells are from bank #4, right cells from bank #9 as they were de-welded from my battery pack few weeks ago.Tomorrow I'll try to charge them full then discharge or the other way around (not sure how this equipment works) to evaluate their respective health through one loop auto test.

author: Tantratron
author_rank: Frequent Contributor
timestamp: August 22, 2025, 12:31:25 pm
content: Hi@Kean, regarding the 3 cells removed from bank #9, here are the test results of looping 1 time for discharge down to 3V then charge.As for the 3 cells removed from bank #4, I'll try later or tomorrow but I think they are not safe or good. Yesterday when I run only charge test, they would never reach max voltage, they would get warm or hot, current still flowing through them so the charging process would never complete.

author: Kean
author_rank: Unknown
timestamp: August 22, 2025, 03:32:04 pm
content: OK, so those results are after charging.What you really want to do now is cycle them 2 or 3 times - charge and then discharge, and record the discharge capacity each time.Ideally the discharge capacity should increase a bit further than than those initial readings.The end voltage after charging is approx 4.1V, which is OK. It should charge to a max of 4.2V, but can quickly drop once charging stops and may settle after some time to around 3.9-4.0V.Charging capacity is over 2000mAh which is a bit low but acceptable for older cells. Note that there is losses during charging so actual usable charge (discharge value) will be lower.A new NCR18650PF is rated for 2900mAh with a discharge cut off of 2.5V, and max discharge of 10A. I am not sure what current that rating is tested at.This tester can only discharge at 1A (fixed?), which isn't a lot for these cells. You can set the stop a bit below 3.0V, but no lower than 2.5V. I normally wouldn't go that low except at high currents.If you can still get 80% of specification (i.e. >=2320mAh on discharge test) on an older battery that is pretty good, but of course you are not testing at the full 10A.These cells should still usable for other less demanding projects.Once done testing, make sure to charge them again. And for storage (more than a month unused), I'd suggest discharging to something between 3.3V and 3.5V.

author: Tantratron
author_rank: Frequent Contributor
timestamp: August 22, 2025, 04:36:48 pm
content: I believe the 4ch charger/tester is the same model you have been using in your company, not sure. Indeed it only charges max to 1A per channel, as for the discharge same max 1A per channel whereas attached an old datasheet i've found about these cells from Panasonic, they test capacity at 4A (see pages 4 and 5).As for the 3 cells from bank #9, I waited few hours after their 1 loop discharge/charge, their voltage keeps 4.11V via my DMM reading so I think these 3 cells are OK for other projects than the eBike 10S5P pack.I'll try later this week-end to test the 3 other cells from bank #4 which I'm pretty sure to be not healthy or not safe because only with charging, they never complete this phase. Furthermore even reaching 4V, they become warm when I touch their body with hand. My hope to solve the initial problem of replacing 20% of cells (full bank #4 and #9) on the 10S5P battery pack was to re-use 5 cells (2016) from both partial failed 2 banks, de-weld 5 cells (2020 purchased from NKON) then spot weld 5 cells (2016) to see if the global balancing would work better.Let's see my further testing but chances are low, i'll only have total of 3 aged but healthy cells whereas I need 5 to make a balanced bank.By the way, I'm still waiting for the delivery of active balancer from Aliexpress to see if it can locally fix the main issue after changing 20% of cells with claimed legit 2020 cells.The other option now that I have this charger-tester will be to top-charge bank #4 and bank #5 as you suggested before to see if the BMS can re-capture a global balance.Another technical question about active balancer, I've seen 2 types: one withcapacitive balancingand another calledinductive balancingDo you know the pros and cons of both balancing circuit concept ?

author: Kean
author_rank: Unknown
timestamp: August 22, 2025, 05:00:45 pm
content: Yes, the charger looks the same as mine - but that means little when buying stuff from sellers on AliExpress, where the products sold change specification all the time.If those specs are at 4A, then testing at 1A isn't too bad compared to the other extreme of 10A.It is quite normal for the cells to get warm during charging, but they shouldn't get so hot that you cannot pick them up. You can see the temperature curve on page 6 goes up to 50C for the PF (110C for PD).I received my 8S balancer a week ago, but I'm busy with another project so I've not tried it. I also got some cheap BMS boards in the mail today.From what I understand the inductive active balancing is usually for lower currents (like 1A or to 2A), and thus smaller sized battery packs. And capacitive balancing is better for larger current (maybe 5A peak or more), and thus larger packs like 100Ah total and above.The sample one I got is inductive, as I'm not currently making such huge packs.

author: Tantratron
author_rank: Frequent Contributor
timestamp: August 23, 2025, 08:12:58 am
content: Quote from: Kean on August 22, 2025, 05:00:45 pmOk then I've re-installed to charge both 3 cells from bank #4 this morning and they finally all reach 4.10 V with the charger/tester stating finish status. They did not heat as the other day so maybe they kind of self-heal or change chemically, no idea. Then I've waited an hour and now, I've launched complete one loop test discharge/charge which will probably take around 4 to 5 hours as the other set yesterday.I've to say this 4 channels charger/tester is quite handy, good, easy to use and correct price so I might re-order a second one to the same seller.N.B. As for your question regarding discharge, when cells are full voltage it will discharge at 1A on each channel but when the volatge decreases the discharge current will decrease. For example now discharging at 0.85 A while 3.42 V. I'll check when it reaches near 3V but I remember it was lesser discharge amperage.

author: Tantratron
author_rank: Frequent Contributor
timestamp: August 23, 2025, 12:56:27 pm
content: Here are now the complete test (loop 1) of the 3 cells taken from the faulty bank #4, this time no overheating when I touched with my fingers, they charge full then discharge down to 3V and recharged full.So technically I have 3 cells (2016) from partially faulty bank #4 and 3 cells (2016) partially faulty bank #9, each 5P bank had 5 cells.BTW. I've been delivered of my 10S active balancer so will solder at some point its 11 wire cable directly into the 10S5P battery pack.

author: Kean
author_rank: Unknown
timestamp: August 23, 2025, 01:29:50 pm
content: I normally use the charge and discharge functions separately so I can see the individual values. The discharge value is the most useful indicator of capacity.Also, forgot to mention that the ESR readings of 73mΩ or so are good. Higher ESR means more voltage drop and heat during charge and discharge. and sign of a failing battery (similar to capacitors).In any case, these cells seem OK for their age.

author: Tantratron
author_rank: Frequent Contributor
timestamp: August 23, 2025, 02:23:57 pm
content: Quote from: Kean on August 23, 2025, 01:29:50 pmWe both have the same unit or model from AliExpress but as you said, maybe not exactly the same version of firmware (mine is 6.1.1). In my case, if choosing AUTO mode then it will first do some charging but will not count any mAh. Only when it will shift to discharging, then it does count precise mAh. Once limit of discharge is reached (i.e. 3V), it will start charging again and not count any mAh. So with AUTO mode in my unit, it only reports and datalogs the discharge capacity.

author: Kean
author_rank: Unknown
timestamp: August 24, 2025, 09:03:05 pm
content: I don't know if I have ever used AUTO mode so I wasn't aware it worked that way.Mine has firmware v4.1.

author: Tantratron
author_rank: Frequent Contributor
timestamp: August 25, 2025, 01:57:26 pm
content: I've now ordered a second 4 ch charger/tester from the same AliExpress vendor so this will be easier for me to run side by side test of the 2x3 = 6 remaining cells (2016).It will take probably 7-10 days to receive from AliExpress the 2nd charger so I'll let the 6 cells fully charged then will DMM test their voltage to see if one is loosing charge quickly. The idea would be in the worst scenario to de-weld 5 cells (2020 from NKON) then re-weld the 5 best cells (2016). If I really go down this road, I'd then check their weight (i.e. 46 g) to see if they are fake because I still feel something is not clear with NKON (why no precise date of manufacturing printed on the 2020 cells green sleeve).In the meantime, the eBike will be run more km to discharge say down to 34 V or 32 V, the idea being to deep discharge each bank (2016 bank and 2020 bank) then see if the BMS can rebalance all the voltages after a full charge. If not then I'll use the external board active balancer from Aliexpress or I'll top-charge both 2020 banks then see if it solves the problem.The more I think about this topic, it seems really a pain to recondition or repair a battery pack if changing few cells:finding an authentic and trusted cell vendor (low MOQ)matching chemical age and manufacturing when replacing failed cellsBMS control law balancing technology

author: Tantratron
author_rank: Frequent Contributor
timestamp: August 26, 2025, 07:00:31 am
content: Quote from: Kean on August 09, 2025, 03:55:14 pmExcellent visual spot and guess, indeed they are not compatible in size neither in polarities

author: Tantratron
author_rank: Frequent Contributor
timestamp: August 27, 2025, 07:32:28 am
content: On second thought, I wonder if after all the NKON batteries are finally legit 2020 because the only picture I took (see attached), we guess date code 0Y20. I've contacted NKON to ask them about the date code formulae and more, they do not know anything neither asked their distributor in China. However NKON is now selling 2021 cells and they gave me one date code 1227 so it seems the first digit would be last digit of year of production. Only question being where does Panasonic prints which decade (2010-2019 or from 2020) on the green sleeve. In my case, the 0Y20 would imply manufactured nov. 20th, 2020 and their new stock 1227 would imply manufactured feb. 27th, 2021On a side note, i've foundanother websiteexplaining date code for 2010 decade which covers the letter X, Y, Z whereasthe Battery Pro date calculatordoes not work with letters. I contacted Battery pro to know the complete formulae, their answers so far are totally incomplete. I've founda battery repair in Swedenthrough YouTube who answered me but still, he does not know either how Panasonic tracks 2010 decade or 2020 decade since they seem to use only 4 character (4 digits or 3 digits + 1 letter).Anyway it seems probably the NKON cells would really legit and authentic made by Panasonic in 2020 if we assume 0Y20 were manufactured in 2020 and not 2010 (the battery would be dead) so the technical challenge is more how to rebalance 2 banks (2020 never used) versus 8 banks (2016 charged around 400 times). The NKON replied me a similar answer than@Kean, namelyThe cells are not balanced, some cells reach the threshold and stop charging. Balancing can be very slow. Capacity mismatch, the voltage of the cells depends on how much they are charged. Of your old cells lost some capacity they will reach the threshold value before the larger cells have change to fully charge. If you can use a lab power supply to charge the banks individually until they reach the desired voltage.Right now the battery pack reached 35V after addition km riding so I'll pursue more rides to go down say 34 V or 32 V then will fully recharge in the hope some better rebalancing can take place via the native BMS. If we go back to the initial post and topic of failure, the BMS would always isolate (disconnect) the battery pack once reaching 36 V due to one 5P bank partially failed. Now this problem is clearly solved so remains to solve the re-balancing if possible after replacing 20% of cells.

author: Tantratron
author_rank: Frequent Contributor
timestamp: August 28, 2025, 08:00:44 am
content: The eBike has run more km and the battery pack reached 33.7 V then started to disconnect then reconnect. So I've removed the battery pack and measured precisely each bank voltage:bank #1 -> 3.40 Vbank #2 -> 3.40 Vbank #3 -> 3.40 Vbank #4 -> 3.11 Vbank #5 -> 3.42 Vbank #6 -> 3.42 Vbank #7 -> 3.51 Vbank #8 -> 3.46 Vbank #9 -> 3.11 Vbank #10 -> 3.45 VSo I still have the non-balancing effect on bank #4 and bank #9 explaining why BMS will cut if one bank reaches 3V.To measure each bank voltage with DMM, I had to access the complete battery pack (i.e. removing partial kapton and other temporary physical protection) then I've now soldered the specific 11 wires cable to be used later with the 10S active balancer board. Then everything has been repacked and re-kapton, now the battery pack is being recharged so the idea is to see if some rebalancing took place via BMS.Depending results, I'll either to-charge both 2020 banks versus 2016 banks to see if it fixes the issue.I need to check if technically possible to bridge the 10S active balancer with BMS then leave always connected during eBike ride (discharge) or eBike recharge. Idea would be to have a reinforced BMS balancing with external board, no idea if this is safe.

author: Tantratron
author_rank: Frequent Contributor
timestamp: August 29, 2025, 07:51:31 am
content: The full recharging yesterday did not solve the rebalancing so i've decided to jump in the pool this morning. I've connected directly the active balancer while BMS connected to the 10S5P pack but no charger neither no discharge.I'm not sure to fully understand all the features and LED indication from the balancer, see attached 2 pictures. The first was when I've connected the balancer board which seems to confirm issue related to bank #4 and bank #9. After say 5-10 minutes, one LED switched off where I assume it took care of bank #4 balancing. However it stayed with the 2 LED related to bank #9 for an hour so I've checked with my DMM each bank which seemed all equalized, no idea why some LED kept being witched on whereas all 10 voltages seemed now perfect at 3.94 V

author: ME
author_rank: Frequent Contributor
timestamp: August 29, 2025, 08:30:51 am
content: Why not fit a bms with blutooth,mine has lots of options for setting the balance parameters+you get to see the cell states on a smartphone.

author: SMdude
author_rank: Frequent Contributor
timestamp: August 29, 2025, 12:04:34 pm
content: Righto, 2 things, ESR and capacity.The banks with the new cells in them have a lower esr than the older banks and will have more usable capacity. The new banks will discharge and recharge at a different rate to the other banks.Charging each individual bank to full voltage to begin with is the correct thing to do, but be aware that the older banks will reach their cutoff voltage before the new banks do. And then whether they charge to full correctly again will need to be checked.Probably the best way to have gone about this repair without a full refurbish would have been to take cells from existing good banks to rebuild the failed banks, then evenly put new cells in each bank, ie 1 new cell in each bank, to achieve the same ESR and capacity across each bank.PS, I do a lot of battery stuff, so not talking out of my ass! Measuring and matching ESR is essential.Cheers

author: Tantratron
author_rank: Frequent Contributor
timestamp: August 29, 2025, 05:38:59 pm
content: Quote from: ME on August 29, 2025, 08:30:51 amThat could be an ultimate choice, actually@Keansuggested 1 or 2 weeks ago that approach as a last chance.For the moment, I'm trying now to use and learn the effect of the 10S active balancer which i connect directly to the BMS prior charging. So far so good, this morning max charge was 39.5 V and now I reach 40V. Then another run of active balancer then when all its LED are off, I recharge full to see an increase 10S5P cumulated voltage.The other option I've still not tried is to do the top-charging of both banks with 2020 cells. This should be easier to do because the active balancing board offers an ease to solder 2 wires for each bank so I'd not need to deconstruct the battery pack casing protection with kapton. Now I've received the second 4 channel charger so rechnicall, top-charging is doable easy but requires strategy because my problem is related to 20% of 2020 cells versus 80% of 2016 cells.Now with new BMS or say a smarter digital BMS wether bluetooh or no bluetooth. Probably there are models that can by software dynamically balance 10S banks and void the issue of old cells mixed with new cells. The all idea being that say a few cells are dead in 10S5P, just not going right away to junkyard and throw everything (pollution, more Lithium mining...), buy new battery or rebuild new battery.

author: Tantratron
author_rank: Frequent Contributor
timestamp: August 30, 2025, 10:25:13 am
content: Another update for what it is worth after i've contacted the AliExpress seller of the 10S active balancer about if OK to leave always connected its board with my BMS. He said it was OK so I've proceeded this time to fully recharge or say complete recharge while 10S active balancer is voting at the same time as the BMS. It does work with no problem where it seems possible to softly increase and balance all the banks including the 2020 which now reach 4 V instead of previous max 3.75 VI fully understand the discharge and charge of 2020 cells will be different than the 2016, the question being if it is an advantage to top-charge max the 2020 cells then later while eBike is running, the 2020 cells would this time have a higher voltage than the 2016.

author: Tantratron
author_rank: Frequent Contributor
timestamp: September 01, 2025, 09:02:56 am
content: Quote from: SMdude on August 29, 2025, 12:04:34 pmI'm not sure to fully understand your approach beause (1) it will require a dewelding and welding huge task (2) testing many cells to know their ESR and mAh health (3) will parallel older cell with newer cell so through time this could degrade the bank. Not saying you are right or wrong but it seems what you suggest is only time/financial viable if you're a company specialized in battery pack repair so you can factorize many tasks, many tests, many used cells...In the meantime to make things simpler, I've kept 2 banks each with 2020 cells assumed to have the same ESR/mAh stored and never discharged to co-exist between 8 banks each 2016 having being charged/discharged around 400 times. To speed the mismatch balancing or slow balancing from the actual BMS, I'm turbo-charging or hybriding this process via an external fast BMS connected to the internal BMS, more details on my video.Time will tell after riding again the eBike in the next months.

author: BILLPOD
author_rank: Frequent Contributor
timestamp: September 01, 2025, 07:45:09 pm
content: I've had several chargers for my cylindrical batteries, but the very best one I have, which also discharges and automatically cycles them, (many settable parameters in the menu). is the SkyRC MC3000. It costs more than the Alliexpress specials, but you get what you pay for.https://www.amazon.com/SKYRC-MC3000-SkyRC-Multi-Chemistry-Charger/dp/B075HRVJ4Q/ref=sr_1_3?adgrpid=1241349658771807&dib=eyJ2IjoiMSJ9.myhcztdUWfIVLsPvDf5S-9h-tz_RwQPQawiHDRtaQFrfaFhQaItZHKOIBE0FcnxiaWNbhPGaUKmp3kce-vLevUQpz__TTgqBZSufcrLALxXlM3T9PwL-5DaGJYEHrtO9UOIAwHdcbyXRVV5h1d1WEf_aqv7iPYYqMRn0OEu5REUJ9XOW6-sDmuI3g2NKDPpNNYEHVbc_iU551iu7bVtJznPGNKDSCxsCD_bKs-orRFI.WNxvbfK4G8idH9ARVS_tlZTk5DSO7muuu6JbwihFmT0&dib_tag=se&hvadid=77584485629453&hvbmt=be&hvdev=c&hvlocphy=105222&hvnetw=s&hvqmt=e&hvtargid=kwd-77584642062895%3Aloc-190&hydadcr=14684_13497504&keywords=mc3000+charger&mcid=f22807538b0c3f5ca04b09b5d2a294a5&msclkid=55937cc812f715e3c957147de753dcef&qid=1756755387&sr=8-3

author: danno_cj
author_rank: Contributor
timestamp: September 01, 2025, 09:49:16 pm
content: The right way to repair the battery is to rebuild with new cells. Buy all the 50 cells from the same place one time. This will guarantee same ESR and same capacity that will make a solid battery pack that will last another 9 years. I fixed this way 10S4P bicycle battery with Sanyo NCR18650GA 3450mAh red one made in China bought from Nkon. It is already 3 years old and is working fine. Take care when closing the case to avoid water ingress.

author: Tantratron
author_rank: Frequent Contributor
timestamp: September 02, 2025, 10:00:50 am
content: Quote from: danno_cj on September 01, 2025, 09:49:16 pmWhat you describe is not a repair but a build or rebuild only keeping the BMS and the spacers.The topic of this thread is repairwhereas other topics or tutorial are maybe build by yourself an eBike battery pack.On a side note as I've explained on my last video, we as engineers and technicians should show the way of ecology, repair and investigate why failure then solve. If we all start to put in junkyard an old battery pack, not checking why it works or fails, how could we re-use or recondition the cells then no wonder our planet is just going CO2 nuts, same with kids working on Lithium mining. At some point we need to be responsible, in particular if we have skills on electronics instead of throw away parts that could still have new life or another use.It is a clear fact that balancing different type of cells is not an easy task, I've made initially a few mistakes but it is a learning curve. Technically speaking in my case, only 4 cells had a problem among the 50 cellls, later I checked with charging/discharging procedure the remaining cells still had an acceptable ESR and mAh charge.All the best, Albert

author: danno_cj
author_rank: Contributor
timestamp: September 03, 2025, 09:15:43 pm
content: Let's think and act from these facts:1. The cells are old with around 400 cycle done so far. I consider those cells at the end of their life.2. The power requirement is really high. The motor can eat 10A for long time, and even more for short periods.3. The battery tester that you're using is not appropriate for your case. The numbers came from discharging at low rate 1A, not high enough to simulate real scenario on bicycle. Check them at 2A or even better at 3A. This will give you the real capacity available on bicycle. The internal resistance provided is a fake one. If 75mOhm is real then your cells are bad. The small 13300 size and 500mAh lithium battery recovered from disposable vape give me 50 mOhm measured with original Yaorea YR1035+. Compare this number with yours in terms like physical size, claimed capacity.4. Balancing the cells with BMS when charging is only half of the story because when discharging with lots of amps they become soon unbalanced. This was already happening to you and the cause is different internal resistance between cells. The load is equal distributed on each group and inside of each group only when the internal resistance is equally matched. The BMS take care for the difference in internal resistance between groups when charging but do nothing on discharging.Already someone else wrote that the battery pack must be totally disassembled and then check every cell. Of course you need two new tools for this. With the money spend on battery discharger at 3A and true internal battery tester you can have all new cells needed to rebuild the battery pack.As for environmental issues I suggest to build power bank/ups from old cells. Charging a laptop or a cell phone don't require brand new lithium cells.

author: Tantratron
author_rank: Frequent Contributor
timestamp: September 10, 2025, 09:02:36 am
content: Hello@danno_cjThanks for additional explanation, suggestions and food for thoughts. It is too bad you did not know or catch up early june when I started this repair and initiated my learning curve. I see there are different shool of thoughts, strategies, trade-off of quality, cost, test equipment and labour. For the moment, it is bit too late to redo or recondition my wife's eBike battery pack which seems to provide decent km range. So far with 8 banks (all 40 cells from 2016 cycled around 400 times) and 2 banks (10 cells from 2020 never used from NKON), the eBike already run more than 100 km after my humble repair at 19081 km (no balancing). For the record after the active balancing last week, its mileage was then 19002 km and last night it was 19068 km without any recharging, the battery read 36.4V while it was recharge to its highest possible 40.4 V so I will see tonight when my wife returns from 20 km ride of the day what battery's voltage. Of course no way to obtain say 42 V max recharging value since cells are old and used so now the question will be to observe the de-balancing effect when eBike run say 50 km or 80 km without recharge.Now for those interested in cheap good spot welder, I've purchased another model from AliExpress still made by same company but using SuperCapacitor technology instead of transformer technology. Both are connected to the AC-grid so we do not have the stand-alone internal Lithium failure issue discussed earlier. See attached picture of the new model (left) and prior model (right) then some pictures of quick testing on my 6 cells (spares removed from battery pack). My first comment, there is a confirmation of initial problem that one cable firm grisp lock issue existed on first model because I've tried all 4 cables combination, the new spot welder is tolerance fine gauged. My second comment, it is very easy to solder, here I've tried gear 13 with 0.15 mm nickel strip and found energy, spark to be smoother and more repetitive (see 2 attached pictures, one pack of positive electrode, another pack with negative electrode). I still wonder of the first model where you are supposed to tune amperage and time, not clear if precise plus if you do many spot welding cells, does it keep its welding factor. My third comment is both have quality screw tip removal solder, both are heavy duty but I notice as shown on my last picture the SuperCap model has wider tip end transformer moidel (right). Of course both have the same Litz wire power cable part number and screw-lock part number.I do not know if some of you are interested to have more testing information or review or pictures, maybe I could do a YouTube video but not sure how to camera film myself while in use. Actually the prices from AliExpress keep changing everyday, every week, no idea why but I was able to purchase this SuperCap model cheaper (61 €) than the transformer model (68 €) all with shipment included to France.

author: Tantratron
author_rank: Frequent Contributor
timestamp: September 11, 2025, 08:36:30 am
content: Quote from: danno_cj on September 03, 2025, 09:15:43 pmI still need to DMM measure each bank to observe precisely the de-balancing of 8+2 banks then check if upon full recharge, the actual low cost BMS will re-balance without the external assistance of active balancer board.In the meantime, here is a synthesis of km range, no initial balancing followed by eBike rides then balancing followed by rides.August 27, 2025 @ 18981 km: 2 banks were spot welded with NKON 2020 cells + 8 banks left with 2016 cells (cycled around 400 times), full recharge reached 39.5 V with NO balancingSeptember 2, 2025 @ 19002 km: full recharging reached again 39.5 V so few alternate cycles of external acyive balancing, full recharge brought ultimately full recharge at 40.4 VSeptember 11, 2025 @ 19086 km: eBike battery packs read 35.4 V so 84 km were ridden without any rechargeMy idea now is to either ride some more distance the eBike or try full recharge without external active balancing to check what max voltage can be reached. The ideal case is to not use anymore the external board doing active balancing (max 1.2 A) versus the interbal BMS balancing (max 50 mA) to see if possible to reach max battery voltage 8*4.0 + 2*4.2 circa 40.4 VQuote from: Tantratron on September 10, 2025, 09:02:36 amI've tried this new spot welder with gear #1 then gear #8 instead of yesterday gear #13 having in mind max gear to be #25 (see attached picture and yellow pointing). Only sht spot welding were done on my actual simple pack, it seems actually gear #8 to be more than sufficient to firmly spot weld 0.15 mm but I do not have spare cells to try. Too much work to de-weld my 6 cells, grind them with my Dremel then spot weld again due to risk of possible damaging structural inetgrity of 1865 panasonic electrodes... maybe the fact I've re-spot welded nickel strip already welded change the result with some bias so only if welding new cell electrode with new nickel strip would be more conclusive.However if some of you living close to my place near Toulouse (France) have some cells and nickel strip thickness to try, you could stop over then we'd verify together the results.Albert

author: Tantratron
author_rank: Frequent Contributor
timestamp: September 12, 2025, 11:08:16 am
content: Here is an update of km range without recharge then recharge with and without final balancing.August 27, 2025 @ 18981 km: 2 banks were spot welded with NKON 2020 cells + 8 banks left with 2016 cells (cycled around 400 times), full recharge reached 39.5 V with NO balancingSeptember 2, 2025 @ 19002 km: full recharging reached again 39.5 V so few alternate cycles of external active balancing board, full recharge brought ultimately full recharge at 40.4 VSeptember 12, 2025 @ 19099 km: eBike battery packs read 34.8 Vso 97 km were ridden without any recharge, full recharge with NO balancing at 40.4 VSo it seems I'm quite lucky (TBC) where the BMS discharge while riding 97 km did not un-balance the 2020 banks versus the 2016 banks then full 36 V-5A recharge provided again 40.4 V with NO external balancing board. This BMS did manage quite well the discharge then recharge of the reconditionned battery pack. The strategy and analysis of@Keanto use external balancing board to solve the issue seems working very good, no need to change 50 cells but only replace 10 cells.

author: Kean
author_rank: Unknown
timestamp: September 12, 2025, 12:23:14 pm
content: A very good result.I think there might be value in keeping the active balancer attached long term. It will consume a little power when on "standby", but it will also avoid any imbalance problems caused due to the different cell ages that might cause the pack to fail again prematurely.On the topic of battery welders, that new one seems to give pretty good results. I did have another play with my Glitter 801D welder which uses super capacitors. It takes quite a while to charge up before use, and must be kept powered from the12V DC15V 2A DC supply while operating. Unfortunately the 1.3mm DC jack used is quite temperamental, which is what was causing my issues - it must be plugged in very firmly else it will not power on.I'd say the weld quality is not quite as good as shown by @Tantratron in the previous few posts, but that could be my technique and/or the difference in supplied probes. It is easy to get a weld, but hard to get a very strong one without instead vaporizing the surrounding nickel strip.

author: Tantratron
author_rank: Frequent Contributor
timestamp: September 12, 2025, 12:46:38 pm
content: Quote from: Kean on September 12, 2025, 12:23:14 pmThe last model which i've purchased (internal supercap welding tech) has an external power supply (100-270 Vac /DC 12 V - 3.5A) to recharge. The jack seems quite strong so far tight once inserted into the main unit. If the external power supply is not connected, the spot welder does not turn on even if supercap are fully charged. With this unit, you can either pedal trigger the spot welding or choose automatic sense delay time.

author: Tantratron
author_rank: Frequent Contributor
timestamp: October 03, 2025, 10:27:46 am
content: Quote from: Kean on September 12, 2025, 12:23:14 pmHere is an update, now the eBike reached 19201 km still recharge without final external balancing neither top-charging.August 27, 2025 @ 18981 km: 2 banks were spot welded with NKON 2020 cells + 8 banks left with 2016 cells (cycled around 400 times), full recharge reached 39.5 V with NO balancingSeptember 2, 2025 @ 19002 km: full recharging reached again 39.5 V so few alternate cycles of external active balancing board, full recharge brought ultimately full recharge at 40.4 VSeptember 12, 2025 @ 19099 km: eBike battery packs read 34.8 Vso 97 km were ridden without any recharge, full recharge with NO balancing at 40.4 VOctober 2, 2025 @ 19201 km: eBike battery packs read 34.2 Vso 102 km were ridden without any recharge, full recharge with NO balancing at 39.9 VYou might be right that at the end, I might permanently solder the external active balancer since we notice max recharge 39.9 V instead of 40.4 V to keep a permanent hybride balancing (BMS max 50 mA and external board max 1.2 A). Let's see through time, in fact not too much ridding because my wife visited our son in Canada 10 days in september but she will resume more use of her eBike from now on.I've made my last video because after checking some other tutorial on YouTube, there might have been an integrity / safety issue with all 11 wires from the BMS. The french manufacturer left them all same size length and grouped them packed in pizza style, I show my redo of this wiring in my last video. Furthemore if later I see the need to reinstall the external active balancer, then I will use same layout on the other side of the battery pack. In the video, I do mention the other balancing solution proposed by@Keanbased on top-charging each new banks to trigger or lock the fact 2020 cells will always be charged higher max than the 2016 cells.