balance charging battery pack method - will it work? SERIES  - Page 1
Forum section: electronics / projects

author: user1235423643
author_rank: Regular Contributor
timestamp: September 12, 2016, 06:29:27 pm
content: hello, i am looking for some advice on this idea.the video linked below shows a cleaver trick to speed up a balance charging, but only 1 CELL at a time.the normal method uses a charge and drain cycle that is also explained in the video.Balancing your lipo battery more quickly (and how cheap chargers work)doing all that is a pain in the ass to be honest. and i want to know if there is any options for a one plug and play fast charge method.the method in mind:we have a 4S battery pack made up of 4 cells at max 4.2vtotal voltage is 16.8vwe could change all 4 at at 16.8v. this is dirty and if the cells are not A1 they wont change the same rate, under and over charging will occur.using the balance lead could we use 4 separate boost \ buck converters cc\cv. set to each cell total to charge each cell individually or something similar.PROS? CONS?** image attachedi have been able to use a small boost\buck cc cv to charge 2S cells of the 4s cell pack at 8.4v . no issues.but where to go from here.thanks

author: MarkM
author_rank: Regular Contributor
timestamp: September 12, 2016, 08:14:27 pm
content: Why not buy a proper LiPo balance charger?

author: Pjotr
author_rank: Frequent Contributor
timestamp: September 12, 2016, 08:24:19 pm
content: Parallel charging is quite old. It is the most reliable but also the most expensive method. It is usually used for high voltage high power banks of 600V --> electric cars.You actually don't need 4 converters for 4 cells. But one converter with 4 separate secondary windings. You will need anyway watching each cell tough. When it is full at 4.1V* that cell is individually switched off while the other cells keep charging.Balancing is automatic this way when charging. At discharging, the cell that gets through its discharge threshold first cuts off the whole battery.* Or the appropriate voltage for the chemistry at hand.

author: Fungus
author_rank: Super Contributor
timestamp: September 12, 2016, 09:06:35 pm
content: Quote from: user1235423643 on September 12, 2016, 06:29:27 pmJust buy a 4 cell charger, eg.:http://www.ebay.com/itm/122086346957(nb. randomly chosen listing...I've never bought/used that item)

author: user1235423643
author_rank: Regular Contributor
timestamp: September 13, 2016, 12:54:59 pm
content: thanks, i see there are "4S Li-ion Lithium 18650 Battery Chargers" on ebaybut i would like to know how they work vs the drain\charge balance chargers.4s is just a example for even larger cells.can cells in the series pack be charged separately at the same time. as shown in the image. and how can this be donehow is it connected up and at what voltages.links or examples would be greatthanks

author: Pjotr
author_rank: Frequent Contributor
timestamp: September 13, 2016, 01:33:01 pm
content: To me it is not clear what the guy in that movie is fiddlingLooks he is just (dis)charging one cell. But why? Not watching all cells at the same time is not a good idea.

author: user1235423643
author_rank: Regular Contributor
timestamp: September 13, 2016, 04:19:09 pm
content: i have been looking at these and none explain what charge input is required to charge the 4s pack, and if each battery is charged separately?i dont need the protection, but i do want to charge the cells in balance.Quote from: Fungus on September 12, 2016, 09:06:35 pm

author: user1235423643
author_rank: Regular Contributor
timestamp: September 13, 2016, 04:21:30 pm
content: hmm...the point of the video is cheap balance chargers take a long time. watch again its well explained. so rather then wait a long time you can charge the low cell up on its own which will speed up the balance charge.Quote from: Pjotr on September 13, 2016, 01:33:01 pm

author: user1235423643
author_rank: Regular Contributor
timestamp: September 14, 2016, 05:30:07 pm
content: does anyone know how to build a basic balance charger for a series 18650 pack. each cell gets its own charge? thanks

author: ajb
author_rank: Super Contributor
timestamp: September 14, 2016, 06:14:15 pm
content: You'd have to have a fully-isolated charging circuit for each cell. That means a separate transformer per cell, or a single transformer with multiple secondaries. One way or another you'll need to monitor and control the charging state of each cell as well. That's the only option.I don't really see what the point is, though. Don't most chargers for series packs charge at a fixed rate until the pack is full, and just shunt excess current past the cells that reach full charge first? So the total time to charge is still determined by the cell that fills up last. The only benefit to independently charging each cell in the pack is that you don't have the power loss in the bypass transistors like with bleed balancing, so some increase in efficiency, but how much difference is that going to make for a 4S pack of 18650s?.

author: Wolf
author_rank: Newbie
timestamp: September 15, 2016, 07:17:56 am
content: Quote from: user1235423643 on September 14, 2016, 05:30:07 pmbattery charge control IC may work, that is what they use in things like e-bike packs and laptops iirc, but I have never bothered to research them, a straight 4 cell 4s 18650 pack I would opt for loose cells in a 4x carrier, if its 4s2p or more in parallel I would then look at pack building....

author: user1235423643
author_rank: Regular Contributor
timestamp: September 15, 2016, 09:56:29 am
content: a few reasons would be, individual charge and the ability to use lower input voltages 5+ volts boost buck cc cvdo you have any more info on the isolation issue?also on bigger packs with shitty cells it would be better balanced with out waste charging and at lower voltages.is there any way cheap way to hack those $1 18650 usb charge moduals to work?thanksQuote from: ajb on September 14, 2016, 06:14:15 pm

author: user1235423643
author_rank: Regular Contributor
timestamp: September 15, 2016, 10:37:40 am
content: http://electronics.stackexchange.com/questions/234086/new-layout-3cell-charger-with-tp4056something like this? why why not

author: amyk
author_rank: Super Contributor
timestamp: September 15, 2016, 10:38:12 am
content: Quote from: ajb on September 14, 2016, 06:14:15 pmNo, all you need is for adjacent outputs to be limited to 4.2V from each other (and current-limited to the maximum cell charging rate.) You don't need to isolate each cells's circuit completely, you just need to use the lower cell's upper voltage (or ground for the lowest) as the basis of each cell's voltage regulator reference.Here is an example, I believe you could reference them all to the same ground if you add additional circuitry to make the V(n) = V(n-1) + 4.2 condition hold for each regulator's output.Edit: see alsohttp://www.linear.com/solutions/5417

author: user1235423643
author_rank: Regular Contributor
timestamp: September 15, 2016, 10:49:18 am
content: http://electronics.stackexchange.com/questions/131309/3-cell-series-li-ion-charging-with-tp4056Quote from: amyk on September 15, 2016, 10:38:12 am

author: Siwastaja
author_rank: Super Contributor
timestamp: September 15, 2016, 11:24:36 am
content: If a battery requires a lot of balancing all the time, it's seriously broken and must be replaced.Normally, the balancer does little work and doesn't limit your charging time much at all, because the cells do keep their balance. When the battery is balanced once, the cells reach 4.20V at the same time, even at quite high charging rates. If some cells is at 4.20V and another one is at 4.19V, it doesn't limit the speed considerably, and even the normal "weak" balancer can do the job.With cell-by-cell separate charging, you could save a few seconds in the normal case.Of course, there are corner cases: if youalwayswant to only fast charge, and never allow full CV phase and never give the weak balancer any time to work, and do this for hundreds of cycles, the imbalance can start affecting your energy storage.Separate buck or boost converters do not work, because what we most often call "buck" or "boost" is a non-isolated topology which shares the ground, so you end up shorting the series cells by connecting the - leads together. Flyback is IMO the best topology for non-dissipative balancing or cell-by-cell charging the series-connected packs, but I wouldn't bother.

author: user1235423643
author_rank: Regular Contributor
timestamp: September 15, 2016, 11:53:45 am
content: thank you for your reply. but i am not looking for excuses, i am looking for solutions to my objective.build a very cheap basic balance charge for each cell in a series pack. if i was not clear the whole point is to balance charge cells that are not the best something of the shelf chargers take forever to do.and ultimately i would like to do it using variable input boost buch cc cv. so it can be charged of any power supply and not need a fancy chargerQuote from: Siwastaja on September 15, 2016, 11:24:36 am

author: ajb
author_rank: Super Contributor
timestamp: September 15, 2016, 12:03:05 pm
content: Quote from: user1235423643 on September 15, 2016, 10:37:40 amThose chargers use a simple linear regulator, and the negative input is connected straight through to the negative output. If you wire them as shown in that diagram, from a single supply, you will short out all of the batteries.Quote from: user1235423643 on September 15, 2016, 10:49:18 amNote that in this case the OP uses a separate power supply for each charger to avoid the problem I mention above. So there are three separate, isolated 5V power supplies supplying the chargers.Quote from: amyk on September 15, 2016, 10:38:12 amThat's a clever part. The charging current for any given cell still has to flow through (or past) any cell below it in the pack, though, which works here because the LTM8052 has a bypass transistor included. So it's halfway between the standard single charger with bypass balancing and fully independent charging of each cell. If the uppermost cell in the pack is the last to finish charging, then there's no advantage at all, since you'll be bypassing all of the other cells until the end of the charge cycle. If the lowest cell finishes last, then yeah, you get the same benefit as fully-isolated charging. Intermediate cases will have intermediate benefit. So it's only halfway to the fully-independent charging I understood the OP to be after.On second thought, I suppose another way to get fully independent charging of each cell would be to do a half bridge + inductor + current sense at each cell junction. Sinking current at a given node would charge the cell above, sourcing would charge the cell below. Turning the bridge off entirely would obviously do nothing. So if you needed to charge only cell B, you could sink from the bridge at B- and source at B+ without doing anything to cells A or C. Possibly still want a balancing circuit to soak up any error, but that would do it with no more components than a separate buck converter per cell would require, at least in principle. I suppose if you went with a boost topology instead of buck you could use a single 5V input for everything.

author: ajb
author_rank: Super Contributor
timestamp: September 15, 2016, 12:11:29 pm
content: Quote from: user1235423643 on September 15, 2016, 11:53:45 amThe cheap and basic solution to what you want is a single buck-boost charger suitable for the number of cells and a bypass balancing circuit. I don't think that anything else will be cheap or basic by comparison, especially since conventional battery charging and protection ICs are produced in such vast quantities. If you're willing to deal with a much messier but still pretty cheap solution, you could use one of those cheap battery charger PCBs per cell and just power each one from a separate wall wart.

author: sleemanj
author_rank: Super Contributor
timestamp: September 15, 2016, 12:26:08 pm
content: Quote from: user1235423643 on September 15, 2016, 10:37:40 amAs ajb says it creates a short circuit because these are not isolated modules, the output negative is connected directly to the input negative, or multiple of them, here I have highlighted in orange how the charger is effectively shorted if you connected power to it, but more dangerously I highlighted how the battery cell is shorted in hot pink because it really will be quite hot if you did this :-)

author: user1235423643
author_rank: Regular Contributor
timestamp: September 15, 2016, 12:51:12 pm
content: "I suppose if you went with a boost topology instead of buck you could use a single 5V input for everything."how so example?what if i used a boost buck cc cv. i think i have seen isolated types?i would really like a simple hacked up 18650 TP4056 modual per cell, or some boost bucks, etc.. the variable input voltage is the key 5v >+ 12v etc4 isolated converters and 4 TP4056 ? still under $10 and can be expanded for as many cells as neededbasically i dont want to have to need special chargers only a voltage input

author: user1235423643
author_rank: Regular Contributor
timestamp: September 15, 2016, 12:57:57 pm
content: how about using diodes? to block that?or something likeDC-DC Converter Isolated Power In 10V-16V Double Out 5V 120505 2W 200mA ULhttp://www.ebay.com/itm/DC-DC-Converter-Isolated-Power-In-10V-16V-Double-Out-5V-120505-2W-200mA-UL-/151063302953?hash=item232c131329:g:xWYAAOSwT~9Whd-oQuote from: sleemanj on September 15, 2016, 12:26:08 pm

author: sleemanj
author_rank: Super Contributor
timestamp: September 15, 2016, 10:38:29 pm
content: Quote from: user1235423643 on September 15, 2016, 12:57:57 pmThen you defeat the purpose, your cells are no longer usefully in series.Quote from: user1235423643 on September 15, 2016, 12:57:57 pmYes you can use anisolatedsupply for each charger board like that, but by the time you buy all the required isolated supplies you are spending just as much as buying an actual multi-cell balance charger. Also note that those isolated supplies have a low current capacity so your charger will be sloooooooow.

author: user1235423643
author_rank: Regular Contributor
timestamp: September 18, 2016, 09:25:45 am
content: hello, you seem to miss the point. i dont want to use a special charger. i want to use a variable input and the boost bucks\ cc cv do the resti need a work around to wire up///also i dont understand "Then you defeat the purpose, your cells are no longer usefully in series." not sure what u think i meanQuote from: sleemanj on September 15, 2016, 10:38:29 pm

author: user1235423643
author_rank: Regular Contributor
timestamp: September 22, 2016, 02:16:39 pm
content: does anyone know a way to make this work?

author: Mechatrommer
author_rank: Super Contributor
timestamp: September 22, 2016, 02:48:25 pm
content: just buy this...http://www.hobbyking.com/hobbyking/store/__64345__Turnigy_Accucel_6_80W_10A_Balancer_Charger_LiHV_Capable.htmlif you are cheap arse, this...http://www.hobbyking.com/hobbyking/store/__58319__Turnigy_B6_PRO_50W_6A_Balance_Charger_Blue_.htmlthey seems to share common FW interface like the clone balance charger that i own bought from china ebay. so i smell an OSHW leak for this, maybe this...https://github.com/stawel/cheali-chargerbut i dont know. i'm not interested in buiding it myself, maybe an opportunity to the OP.disclaimer: i'm not affiliate of hobbyking, just an occasional customer. mostly i will buy from ebay china if i have better deal.

author: user1235423643
author_rank: Regular Contributor
timestamp: October 11, 2016, 08:52:55 am
content: ok again... i dont want to use a external specific charger.is it possible to use something like this with DIODES so not to short out?

author: ajb
author_rank: Super Contributor
timestamp: October 11, 2016, 11:59:55 am
content: No.

author: user1235423643
author_rank: Regular Contributor
timestamp: October 12, 2016, 01:55:04 pm
content: why not?

author: ajb
author_rank: Super Contributor
timestamp: October 12, 2016, 04:13:15 pm
content: Because in order to keep the chargers from shorting out you'd need a diode between the two batteries with cathode at the positive of the lower battery and anode at the negative of the upper battery. In that orientation, the diode will also keep the batteries from discharging. That's what sleemanj was telling you.You could use an active switch between the two batteries, but that's not going to be a simple solution like you keep asking for.

author: user1235423643
author_rank: Regular Contributor
timestamp: October 12, 2016, 04:55:38 pm
content: hmm ok, so why cant the diode be put in line with the negative out of each charger which will still the back feed of + ? or on all the + which everalso option of using cheap dc to dc isolators?http://electronics.stackexchange.com/questions/234086/new-layout-3cell-charger-with-tp4056

author: ajb
author_rank: Super Contributor
timestamp: October 12, 2016, 05:08:24 pm
content: Quote from: user1235423643 on October 12, 2016, 04:55:38 pmThere is no way to add diodes to the circuit to prevent shorting out either the battery or the charger without also preventing the use of the batteries to power a load. The diodes you've drawn there will not even protect against shorting out the chargers, because they will all be forward biased when the chargers are powered on!QuoteYes, as has been mentioned repeatedly, using isolated DC to DC converters or isolated wall warts would be the only way to make your proposal work. However, if you go the isolated DC-DC route, be aware that all of the really cheap DC-DC converters are only good for a watt or two. If you want to charge the battery at 1A, you will need at least a 5W converter. This will maybe not be so cheap, by the time you buy one per cell.

author: Siwastaja
author_rank: Super Contributor
timestamp: October 12, 2016, 05:28:23 pm
content: Your circuit is just perfect and will work perfectly, no need for diodes, just buy and connect everything together and you'll see! Your idea is so brilliant that I suggest you test it using as big cells as possible, for a great demo.

author: user1235423643
author_rank: Regular Contributor
timestamp: October 13, 2016, 10:31:44 am
content: thanks can you please explain why the diode idea wont work?what i have been told is the feedback of - and + on the common outputs will short but i dont understand how if diodes are used. thanksQuote from: ajb on October 12, 2016, 05:08:24 pm

author: sleemanj
author_rank: Super Contributor
timestamp: October 13, 2016, 10:50:58 am
content: Quote from: user1235423643 on October 13, 2016, 10:31:44 amBecause the modules are not isolated, the IN- and OUT- are effectively directly connected so you will create short circuits, eg...Actually that's only because you drew one of the diodes backwards (right most)But even if you corrected that error, you can see without using isolated supplies, the charger board is still shorted on it's output, if the B+ has a route to the B- (even if it can't get to the battery because of your diode) then it is shorted out.If you provided this circuit with isolated supplies (and didn't connect them on the supply side as you showed) it would be fine (as has already been said to you), if you don't, then you shorted out your supply, the boards, and at worst, the batteries.Also how will the devices sense the cell voltage if they are behind diodes. Answer: not well.

author: user1235423643
author_rank: Regular Contributor
timestamp: October 15, 2016, 06:53:20 pm
content: thanks for the reply. but how is it flowing back if the diode is blocking the +/- flowing into the -/+?from what i was told the - or + of the battery would short the output of the chargerQuote from: sleemanj on October 13, 2016, 10:50:58 am

author: sleemanj
author_rank: Super Contributor
timestamp: October 15, 2016, 09:06:40 pm
content: Quote from: user1235423643 on October 15, 2016, 06:53:20 pmIt has been explained to you multiple times, there is no isolation in to out, there is no other way to explain this, the only way you can make your plan work is with some manner of isolated supplies for each board, if you try anything else at best it won't work, at worst something will explode. Be my guest to try, but at least do it outside so you still have somewhere to live after the fire.

author: user1235423643
author_rank: Regular Contributor
timestamp: October 16, 2016, 09:02:26 am
content: ye ok dude, thats isnt answering why and what is going on for it not to work.how can it short if the diodes are blocking the polarities mixing. if you cant explain or dont know how to answer, leave it for someone who can. thanksQuote from: sleemanj on October 15, 2016, 09:06:40 pm

author: cs.dk
author_rank: Unknown
timestamp: October 16, 2016, 09:14:50 am
content: Quote from: user1235423643 on October 16, 2016, 09:02:26 amAnswer people like that won't help you..That is drawn in the post right up above

author: user1235423643
author_rank: Regular Contributor
timestamp: October 16, 2016, 03:00:38 pm
content: right.... how does that explain how the + is flowing back up the - if there are diodes??? it should only allow flow in one direction?? so again if you cannot help explain dont bother to comment. thanksQuote from: cs.dk on October 16, 2016, 09:14:50 am

author: CraigHB
author_rank: Regular Contributor
timestamp: October 16, 2016, 04:32:10 pm
content: The attached drawing in reply number 13 shows how to do what you are wanting to do. I'm surprised nobody emphasized it within the good number of replies afterward.Basically you use a single cell charger on each cell with a virtual ground as shown in the drawing. This is not the same method as used in the video posted in the original reply. That method is used by hobby chargers which may charge at rates well above 2C. Batteries used in powered models may have acceptable charge rates up to 10C. Hobby chargers use a pack charge (only two wires) then during the final CVM phase of charging the charger balances cells as shown in the video. There's a few reasons why hobby chargers balance this way, but none of them apply to your application. The best way to charge series cells in your case is by using the method shown in the diagram of reply 13.One thing to keep in mind is the power you have available to charge with. You mentioned 5V a few times so I assume you're using a USB source. Those are typically limited to an Amp with specialty chargers going as high as 2.1A such as those used for iPhones and Blackberries. Since voltage has to be boosted somewhat above terminal battery voltage, charge rate will be reduced accordingly. For example a typical limit for a USB port would be 5W. At 20V you'd be limited to a 250mA charge rate neglecting losses.

author: ajb
author_rank: Super Contributor
timestamp: October 16, 2016, 05:02:38 pm
content: Quote from: CraigHB on October 16, 2016, 04:32:10 pmYes, conceptually that will work, but not with the TP4056 chargers the OP wants to use, which have an absolute maximum input voltage of 8V. That isn't really even going to be enough to be able to do two cells in series. For the overall system to not be horrendously inefficient you'd need to use some sort of switching charger topology.Quote from: user1235423643 on October 16, 2016, 03:00:38 pmIf you don't understand the problem from the diagrams and explanations that have already been provided, I suggest you try working through it yourself. Start with the application schematic from the TP4056 datasheet, noting in particular that the negative terminal of the battery is connected to the charger's ground. Place two of these schematics together, and connect them up the way you're proposing. Now trace out where current flows through the circuit, starting from your positive supply. Be sure you understand how diodes work so that you can identify whether or not current will flow through them. (We'll leave aside the problem of placing diodes in series with the battery that was explained in your other thread for the moment.) Post your work here, and I'm sure people will be willing to help you understand. The forum best helps those who help themselves.

author: user1235423643
author_rank: Regular Contributor
timestamp: October 18, 2016, 01:00:38 pm
content: hellowhat i am not understating is the issue is suppose to be the mixing of the + and - of the battery's with the output of the chargers.ie. backfeeding + into - and - into +a diode is suppose to allow flow in one direction?if i am blocking the directing what is the problem then?there must be a youtube video that can help explain this better to me?thanksQuote from: ajb on October 16, 2016, 05:02:38 pm

author: user1235423643
author_rank: Regular Contributor
timestamp: October 18, 2016, 01:04:50 pm
content: thanks for the info, im not looking to run off 5V usb either a power suply. also looking to run of a boost\buck so i can charge from any good supply voltage,do yo have any more info about the image in post 13?basically i want a very cheap way to charge mixed 18650s in series so they are balanced and the charge time is not wasted on discharge \ balance. thanksQuote from: CraigHB on October 16, 2016, 04:32:10 pm

author: ajb
author_rank: Super Contributor
timestamp: October 18, 2016, 04:28:26 pm
content: Quote from: user1235423643 on October 18, 2016, 01:00:38 pmYou're not blocking the problematic current with the diodes oriented as you've drawn. If you oriented the diodes to block the problem current, you would also block the charging current. Draw out the circuit and see for yourself. You're also continuing to ignore the fact that diodes between the batteries and charger are a bad idea, as pointed out in your other thread.Quote from: user1235423643 on October 18, 2016, 01:04:50 pmBalancing doesn't waste any time at all. It doesn't matter if you charge each cell separately at 1A or the entire pack at 1A, the time it takes the whole pack to finish charging will be determined by the time it takes the last cell to finish charging. For all of this effort, you will not save any time.

author: CraigHB
author_rank: Regular Contributor
timestamp: October 18, 2016, 04:41:04 pm
content: Quote from: user1235423643 on October 18, 2016, 01:04:50 pmThat makes things a lot easier then since you have a range of voltages and currents available limited only by your power supply. You can use whatever rate you want at whatever voltage is required. Though there is the limitation of the charger controller chip you use which is typically an Amp for the linear type.There is the option of using a buck type charger controller which can support higher currents. Usually when charging 18650s a 1 Amp rate is adequate though it will only be about 1/3C for a typical 18650 cell. The charger controller you mentioned is the linear type which is limited by the power dissipation of the chip, that being the difference between input voltage and battery voltage times rate. From my experience a linear charger controller having a thermal pad soldered to a ground plane tops out about an Amp when driven with a 5V supply.It's a pretty simple thing to put charger controllers in a ladder to charge a series pack of Li-Ion cells. I've not actually built a charger like that so I can't speak from experience. I've done a number of single cell chargers though. The poster above stated that voltage tolerance for each chip in the ladder must be greater than input voltage, but I don't believe that's the case. The ground for each chip is referenced to the plus minus connection of the cell in the battery it's charging so it's never going to see full input voltage.The simple linear controllers you mentioned should work in a ladder. If there's any doubt about voltage tolerance you can always put a charger front end in front of each chip such as the TI BQ24316DSJ. Or you can use a charger controller with a higher voltage tolerance. There's also the option of a buck type charger controller to support higher rates.

author: ajb
author_rank: Super Contributor
timestamp: October 19, 2016, 04:34:11 am
content: Quote from: CraigHB on October 18, 2016, 04:41:04 pmLook at the diagram in post #13 again. The bottom charger in the ladder sees the full 20V input. You could do something like have a different step-down converter for each 'rung' of the ladder such that each charger only saw 5V or whatever at its input, but unless all of those converters are setup to track the battery voltage, the input voltage to each charger will be larger when the pack is discharged, and a pack with many cells in series could wind up violating the max input voltage of one of the middle-ish chargers.But there's actually another, more insidious caveat with that topology, which is that the charging current for any of the upper batteries must flow through all of the batteries below it. That means that if one of the lower cells reaches full charge first, the upper charger will wind up overcharging the lower cell as it attempts to finish charging its cell. The only way to avoid that is to use two-quadrant chargers that can sink current as well as source it to prevent overcharging or--surprise surprise--use an additional balancing circuit. The LT part linked earlier in the thread would work, since it's two-quadrant. It's also a switching topology, so it would be more efficient as well. The TP4056 is NOT two-quadrant, so on its own would not be a good choice for this topology, even if its max input voltage weren't a problem. The overcharging problem is compounded by the fact that, since the charging current through any battery will be the sum of the charging currents supplied by all of the chargers at or above its level in the ladder, if all the cells are similar the lowest cells will always finish charging before the upper cells--if they don't die from excessive charging current first. Again, you could avoid all of these problems by using a separate isolated supply for each charger+cell, or by using a single charger for the overall pack plus a balancer.

author: user1235423643
author_rank: Regular Contributor
timestamp: October 20, 2016, 09:19:16 am
content: "Balancing doesn't waste any time at all. It doesn't matter if you charge each cell separately at 1A or the entire pack at 1A, the time it takes the whole pack to finish charging will be determined by the time it takes the last cell to finish charging. For all of this effort, you will not save any time."that make no sense at all....did i understand the video wrong??https://youtu.be/wIbHLacozFo?t=368where he explains the balance charger will charge in parallel and once a cell reaches full, it STOPS and discharges them.(there for not charging and wasting time discharging)and when charging a series pack in parallel is each sell getting - 1000mah / 3 = 333mah or each cell is getting 1000mah l (max) ??again the point is to find a way to charge a mix 18650 that may not be the same condition, quickly with out wasting time to discharge.even a cleaver way to put a switch between each cell to isolate them while charging is a more simple option.the battery packs will be running boost converters anyway and using recycled battery'sforget the diagram #13 is was just a example i found, i am looking for a solution's not an excuse. thanks