Lipo arrives at 1.27V.  Is that a deal breaker? - Page 1
Forum section: electronics / beginners

author: Peabody
author_rank: Super Contributor
timestamp: February 02, 2018, 02:31:06 am
content: I spent two whole dollars for a "new" BH6X lipo cell. The box it came in has a date on it of May, 2014, and it measures 1.27V. Should I even try to charge it up, or does voltage that low kill it?Also, can I just solder wires to the little connector tabs?What I really need is a battery with wires already coming out of it, and no bigger than 64 x 35 mm. Any suggestions? Doesn't have to be protected since my charger will have all that.

author: viperidae
author_rank: Frequent Contributor
timestamp: February 02, 2018, 04:46:44 am
content: I'd give it a charge for a few seconds. It could be the internal protection has disconnected the output and needs a charge current before it reconnects it.

author: james_s
author_rank: Super Contributor
timestamp: February 02, 2018, 05:49:52 am
content: If you find that it doesn't rapidly wake up, or lacks a protection circuit then ask for a replacement. It's not safe to charge up a LiPo that has sat at such a low level for a long time.

author: Mr.B
author_rank: Unknown
timestamp: February 02, 2018, 06:19:54 am
content: Quote from: viperidae on February 02, 2018, 04:46:44 am+1Charge for 5 seconds and test the open circuit voltage.If it has jumped up to anything above 2.9v you should be pretty safe.

author: Mr.B
author_rank: Unknown
timestamp: February 02, 2018, 06:24:28 am
content: Quote from: james_s on February 02, 2018, 05:49:52 amBeing an industry standard user replaceable cell phone battery, I would expect it to have built in protection.I may be wrong...Regarding soldering on to the connection/landing pads...I wouldn't.You don't know the exact internal construction and how they are connected to the protection circuit.It may be OK if you are quick enough, but I personally would not do it.

author: digsys
author_rank: Unknown
timestamp: February 02, 2018, 06:42:17 am
content: Slightly different opinion here -IMO, we often drive EV / Solar Li packs (of all types) to below 1V per cell. As long as they are under a calculated current profile (at that voltage ~ 1/5C),they suffer NO ill effects. These are not like lead-acid, that degrade badly under ~10.8V.I'd run ~ 2-3 full charge - discharge cycles and see what improvements you see. That will tell you their state and condition.We also solder many tab types. If you don't let an ultra-hot iron on it for ages, it should be perfectly fine. YMMV :-)

author: IanMacdonald
author_rank: Frequent Contributor
timestamp: February 02, 2018, 07:26:29 am
content: Correction, should have noticed, LiPo. Not advisable with those. Send it back.

author: paulca
author_rank: Super Contributor
timestamp: February 02, 2018, 10:18:20 am
content: Quote from: IanMacdonald on February 02, 2018, 07:26:29 am+1A recovery charge is very, very low current. 50mA sounds fair.As to "Yea, it'll be fine", it might be. However LiPos are not LithiumIon or lead acid. The chemistry requires a voltage to hold it's structure. If the voltage gets to low the chemistry starts to break down. Applying current to a cell where the chemistry has gone bad can cause it to overcharge at a much lower voltage than the 4.2V per cell. So when you attempt to charge it to 4.2V per cell it would be like charging it to 4.3V. In short they can and have burst into flames.Give it a refresh as Iain suggests at 50mA to at least 3V.Let it rest for an hour and check it holds the 3VEase it up to nominal (~3.7V) and let it rest again to make sure it holds that voltage.Then fully charge it gently to 4.2VDO NOT TAKE YOUR ATTENTION OFF IT.If it puffs up at all, disconnect it. It should not get even slightly warm at low charge current.Have a metal tin and some oven gloves handy to get it outside if it suddenly expands or heats up.If it won't hold voltage it's a goner and trying to force it will probably result in an ugly response.

author: amyk
author_rank: Super Contributor
timestamp: February 02, 2018, 11:59:52 am
content: Storing cellscompletely emptymay actually be the best for reducing aging capacity loss:http://jes.ecsdl.org/content/163/9/A1872.fullhttp://jes.ecsdl.org/content/164/1/A6066.fullIn fact, articles like this one suggest that cell manufacturers may already be producing ones that are completely fine with being stored at nearly 0V.http://pubs.acs.org/doi/abs/10.1021/cm702290pThere's also this, which studiessevereoverdischarge (as in, cell voltage becoming negative):https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4957210/"The results of the non-ISCr cells suggest that if the overdischarge is terminated before point B at approximately -12% SOC (the first platform after the occurrence of the minimum voltage), the cell can be fully charged back and reused with only minor side effects."-12% is well below 0V.I'd agree with all the others that it would probably be OK after a very slow charge up to normal empty voltage (~2.5 to 3V) and then normal charging to full.

author: paulca
author_rank: Super Contributor
timestamp: February 02, 2018, 01:53:15 pm
content: Note that while there are discussions on how the chemistry in many Lithium-Ion cells are actually Lithium Polymer the chemistry are quite different.LiPo's are typically geared to high current output, short cycle batteries. Lithium Ion are typically geared towards lower current output and longer cycle.LiPos are much more sensitive to over discharge than lithium-ion. IIRC the chemical polymer that holds the charge will not retain it's polymer state below a certain charge and effectively becomes a "short spot" in the cell. This is why charging heavily over-discharged LiPos can be dangerous. Those "short spots" can generate heat. The hotter the compound is the higher it's output voltage. When fully charged this can cause a cascade thermal runaway where the cell heats itself up into an overcharged state which generates more heat and PUFF, BANG, FLAMES!

author: paulca
author_rank: Super Contributor
timestamp: February 02, 2018, 02:06:56 pm
content: By the way, I thought I'd leave this here.NOTE! As to not scaremonger, these are deliberately overcharged batteries, however the thread on RCGroups where LiPo fires are discussed including real unfortunate examples, the makers of this video pointed out that some of the trigger batteries did not been to be overcharged by that much, I believe 4.35V was enough in one case to cause a full on flaming nightmare.

author: soubitos
author_rank: Frequent Contributor
timestamp: February 02, 2018, 02:42:09 pm
content: This is one of the reasons this is useful (actually one of the reasons i made these modules in the first place)https://www.tindie.com/products/11347/Unless you go for much more expensive chargers this module can charge your cells with as low as 60mA.And that is what you should do (some suggest even lower charge currents but 60mA cannot inflict any damage), charge the cell for 10-15minuts with a low current like that, if possible monitor its voltage and temperature...If it gets hot at any point and by hot i mean (for that low current) even a few degrees up is not going to be good, stop charging and dispose safely/recycle the cell. If its voltage raises, and i wouldn't expect it to do otherwise, you can leave it charging slowly until it reaches 2.8-3V... at that point, i would stop charging and let the cell rest 1-2 hours.. if the charge is stable (if was 3V and 2hrs later is 2.95 its more than fine, if its 2v its a no-no) you can resume charging with a higher current...BH6X is a 1800mAh battery for phones, and older ones also (2010-2011 era) which makes it only natural to not take it too high... i would charge this with a "standard" USB charge current of around 500mA, maybe 100-200mA more but only while monitoring its temp

author: Nusa
author_rank: Super Contributor
timestamp: February 02, 2018, 03:11:24 pm
content: QuoteEvery phone brand has their own version, and none interchange with any other brand as a rule. Ditto for most other consumer devices that use pouch cells.The 18650 is the only thing that's even close to a standard, and they aren't used in phones. USB/Phone power packs probably use them, however.QuoteProtection would be part of the cell phone, not the battery, under software control.

author: Audioguru
author_rank: Super Contributor
timestamp: February 02, 2018, 03:56:50 pm
content: The Motorola BH6X Battery in Google lists for $49.99 but since it is obsolete it is on sale for $19.99. One place sells them for $4.95.I think your $2.00 one was worn out and was thrown away. Why did you buy cheap used old junk?I have the Lithium-Ion battery from my daughter's first cell phone, it has been sitting unused for about 16 years and still holds its 3.7V storage charge.

author: paulca
author_rank: Super Contributor
timestamp: February 02, 2018, 03:57:03 pm
content: Blueskull, when was the last time you bought a phone?They don't come with replaceable batteries anymore. To replace the battery you need to open the case (not that easy), unglue and desolder the battery.

author: Peabody
author_rank: Super Contributor
timestamp: February 02, 2018, 10:21:08 pm
content: Thanks very much for everyone's responses.I have a TP4056 module on order, but it's probably two weeks away. And I don't know if it can be set as low as 50 ma charging current. Meanwhile, I have an 18650 charger that's rated at 650 ma. Even if I connect it to the BH6X through an 84-ohm resistor, it will probably shut down, or not start up at all, because the 50 ma would be less than 10% of the full charging rate. So would it be ok if I just adjust a 317 regulator to 4.2V, and use the resistor with that, at least to start with?Other interesting things:I pulled back the tape cover a bit, and it turns out that the metal case is connected to the + terminal. Wasn't expecting that.Are there wires coming out of the battery that connect to the contact tabs? If I remove the black plastic perimeter casing, would I have something to solder to? I need wires, not contact tabs. Well, I guess I've got the whole case I could get + from. So what about ground? And I will have protection in my TP4056 module, so could do without that in the battery if necessary.And Audioguru, the Ebay listing said it was brand new, and from the packaging I suspect it was. But the ad didn't say it was that old. And of course it's not a genuine Moto battery.

author: amyk
author_rank: Super Contributor
timestamp: February 03, 2018, 02:27:55 am
content: QuoteIt's not actually a pouch cell, but prismatic:Quote from: paulca on February 02, 2018, 01:53:15 pmYou may want to readhttps://www.eevblog.com/forum/projects/lithium-ion-charging/msg624770/#msg624770Also read the rest of his posts inhttps://www.eevblog.com/forum/projects/diagnosing-lithium-cells/, it's someone who researches lion cells.

author: paulca
author_rank: Super Contributor
timestamp: February 03, 2018, 05:58:25 am
content: Quote from: amyk on February 03, 2018, 02:27:55 amLet's see. 10 years of experience with LiPos that would eat all the lithium ions I have seen for breakfast, reading and seeing experiments from dozens of people who actually use them in the real world, reading battery datasheets and test results, and then one guy on a forum who doesn't even present backings for his facts... which do I believe.He is correct in some of the posts I read, but seems to miss some of the details/point. Yes they are all Lithium Ion technology. Lithium polymer is a type of Lithium Ion, but they are not the same. The original solid electrolyte idea "plastic" lithium ion that the Lithium Polymer name was born from might not have been fully realised, but the cells are still not the same. They are designed for different applications using different details in the cell chemistry and construction.I don't see anyone using 18650s to run a 700 size heli on 150 Amps.The rant he has about the 3.6/4.1 versus 3.7/4.2 ... as I understand it Lithium Ion's of old in the 90s used to be 3.6/4.1, but have since moved onto 3.7/4.2 as technology improved in the new century. Battery charger manufacturers have been confronted about this and pointed out that they leave the 4.1V charger mode there because you can use the LiPo mode for 4.2V cells. The 4.1V program is handy if you don't want to max the cells out, or just happen to have some much older Ion cells.So, arguments about nomenclature asides they are not the same and have different particulars and different requirements and applications.Lets look at practicalities. In front of me I have two batteries.A Turnigy LiPo 5000mAh 3 Series 30C/50CAn 18650 5200mAh 3S2P laptop cells.Should I charge them the same way? Can I fast charge the 18650s at 20 Amps? Can I discharge them at 150Amps with 250Amp bursts, will they start my car? Should I discharge the LiPo down to 2.75V per cell?You can if you want, but please video it.EDIT: On those BMS boards. Based on the test results I have seen for them. I might trust them to charge a small cell or a metal cylindrical Ion cell, but I would not trust them to charge a large LiPo. The cut off voltages and charge current accuracy is pathetic. Some charge as high as 4.3V, others discharge as low as 2.3V. However I have ordered a bunch of them to test myself, but I don't hold much hope for them. The multi-cell BMSs are even worse. So I'll stick with my hobby grade chargers which have tested over the past 10 years and while their voltage accuracy can be out, it's usually by less than 25mV and I've never seen one that read low. They always read high for safety.

author: Nusa
author_rank: Super Contributor
timestamp: February 03, 2018, 06:52:13 am
content: QuoteDepends on the specific cells used and the pack configuration. Reading the datasheet for the battery in question will give you the manufacturers answer to those questions. You do the math for packs. "Can I" questions exceeding those limits are usually trading away cycle life, if it works at all. "Should I" questions are usually a disguised "Can I" question.

author: james_s
author_rank: Super Contributor
timestamp: February 03, 2018, 08:29:21 am
content: Lithium ion is a broad category of which LiPo is a sub category. Likewise Vehicle is a broad category while "car" is a sub category. There are many different types of lithium ion batteries with varying characteristics.

author: Peabody
author_rank: Super Contributor
timestamp: February 03, 2018, 02:48:05 pm
content: I farted around with the battery this morning to see if I could get any response. I rigged up a testing circuit that goes from a regulated 5V supply, through a 1N4001 diode, then through a 33-ohm resistor to the battery. When connected, the votage across the battery is about 2.5V, and the current is about 40 ma. At first I thought that was a bad sign, but after messing with it for a while taking measurements, I went back and checked the battery voltage, orignally 1.27V, and it's now 2.5V. So apparently that little charging I did either woke it up, or got it up to the point that it's at least measuring as fully discharged, and not something totally wonky.So now I need to solder wires to the contact tabs, and rig up some kind of constant current circuit to charge it at 40-50 ma until it gets up to at least 3V. But I remember something about the LM317 not working well at these low voltages.If I set up an NPN transistor with the right emitter resistor to ground, and then set the base voltage for a given drop across the emitter resistor, will that produce a constant current through the collector for any collector voltage? Seems like it would. Then I would connect the battery positive terminal to a 4.2V regulated supply, and the negative terminal to the collector. What do you think?Anyway, I think this has some chance of working. But I have to say - this battery is rated at 1800 mAh, and there's just no way. It's 64 x 41 x 6 mm, and comparing it to other lipos I have, unless there's special magic of some kind, this battery has to be more like 1200 mAh or less. That would work ok, but, you know, it's not nice to fool mother nature. :-)

author: Ian.M
author_rank: Super Contributor
timestamp: February 03, 2018, 03:08:46 pm
content: Don't solder to it yet as there is a fair chance you'll need to reject it if it doesn't recover or has far less than rated capacity. The easy way to attempt recovery would be to charge it from a much higher voltage through a diode and series resistor, with a 3.9V Zener across the cell to prevent it overcharging. Check the Zener voltage is under 4V with no cell connected - if its over, try another Zener or reducing the current.

author: paulca
author_rank: Super Contributor
timestamp: February 03, 2018, 03:34:28 pm
content: If you have a bench supply with CC, CV modes, put it on 40mA 4.2V and it will take care of it.

author: Peabody
author_rank: Super Contributor
timestamp: February 03, 2018, 05:12:30 pm
content: @Ian.M: The battery cost $2, so I doubt I'll be sending it back. And I don't have a connector that matches the contact tabs, so soldering wires to them is pretty much the only way I can do the charging. And I need the wires for my ultimate intended use.@paulca: Unfortunately, I don't have a bench supply. Didn't Dave do a review of a $20 one recently. I probably need to get one of those.But I think I have the NPN transistor circuit figured out. The regulated power suppy is a convenient 5V, not 4.2V, and the emitter resistor to ground is 16 ohms. There is a 1K pot from +5V to ground, with the wiper connected to the base of the NPN, and that's adjusted until (after the base-emitter diode drop) the voltage at the top of the resistor is 0.8V. At that point, emitter current will be constant at 50 ma., over 99% of which will also be collector current. The battery will be connected between +5V and the collector. The maximum voltage it will see is 5V - .8V = 4.2V if the transistor is fully ON.Current can go above 50 ma only if the voltage across the emitter resistor increases. But if it does, gate voltage will become reverse-biased, which will shut down the transistor. And if the voltage across the resistor drops below 0.8V, more gate current would flow, and the gain of the transistor would immediately bring it back up to 0.8V. So current is constant. That's my story, and I'm sticking with it.I would have to watch for when the battery voltage gets up to a partially charged level, and turn the charger off at that point. If left on, the charger would just keep supplying 50ma at 4.2V even after a full charge is reached, which is not what you want.Anyway, I'll try to set the curcuit up later today and see if it works. Film at 11.

author: Peabody
author_rank: Super Contributor
timestamp: February 03, 2018, 09:57:29 pm
content: My pretend constant current 50 ma charger worked fine. I got the battery up to about 3V, and am letting it rest for an hour. Then I'll try to take it up in stages, then switch over to using a real lipo charger to finish off. Then I'll have to do some discharge/recharge cycles and see how it performs. But at this point I'm enouraged that it may work out ok. Thanks for everyone's help.

author: james_s
author_rank: Super Contributor
timestamp: February 04, 2018, 01:01:00 am
content: Is it worth a house fire to save a $2 battery? Granted one that small is not going to create a big fireball, but I certainly would not leave it on any flammable surfaces.

author: timb
author_rank: Super Contributor
timestamp: February 04, 2018, 01:37:45 am
content: Quote from: paulca on February 03, 2018, 05:58:25 am18650’s are commonly used for electronic cigarettes. For this, they’re commonly used in single and dual (parallel, occasionally series connected) configurations. In the simple mechanical mods, the batteries are hooked directly to the coils (a 0.1 to 5 Ohm Load) through a switch; in the more advanced configurations they power a buck/boost converter, which is capable of delivering up to 200W for 5 to 10 seconds at a time.That’s a lot of power out of what you call a low current cell. (In fact, I’ve got some IMR18650 cells here rated for 30A continues output.)Laptop battery packs also traditionally used 18650 cells and were capable of putting out tens of amps, and that was 20 years ago!Tesla battery packs are made out of 18650 cells and can be fast charged.By the way, the aforementioned IMR18650 cells are pretty cool. These don’t have built in protection circuits as they’re Lithium Manganese. This chemistry means the batteries don’t violently explode if damaged or overheated; instead they heat up a bit, maybe put out some smoke and then slowly break down. There’s also the newer INR cells, which are Lithium Manganese Nickel. These have the thermal stability of IMR cells, but can put out over 50A!In fact, the only real advantage Lithium Polymer cells have is that they can be custom manufactured in a specific size and shape, allowing you to pack more capacity into a given area then you could with 18650 cells. (Which is why high end laptops now use internal LiPo packs, instead of external packs filled with 18650s.)The other advantage LiPo has is in the number of discharge/recharge cycles (500 to 1000 for high end cells). Though, modern Lithium Ion chemistries are catching up—if not surpassing—LiPo in that area.So no, 18650 cells aren’t relegated to low current usage.

author: james_s
author_rank: Super Contributor
timestamp: February 04, 2018, 03:57:12 am
content: It's worth remembering that 18650 is a physical form factor, cells of widely varying characteristics are available in that form factor. It's been a while since I've looked at a datasheet for a typical laptop cell but I recall seeing a spec of something like 2C max continuous discharge rate and 1C fast charge.There's a reason that electric RC aircraft and other vehicles almost universally use LiPo batteries rather than 18650 type cells. It's very common to have single LiPo cells that are rated to supply a continuous 30C or more, that can be charged at 5C or in some cases 10C while still offering a few hundred cycles.The price to pay for this is they are somewhat temperamental, if you abuse them by drawing too much current or discharging excessively they puff up and the IR increases dramatically. If you overcharge or physically abuse them they burst into flames, I've seen it happen before, somebody crashed a large electric helicopter at the field while I was flying planes, the thing made a fireball shortly after impact. There have been a number of house fires posted on the RC forum, mostly charging accidents.

author: paulca
author_rank: Super Contributor
timestamp: February 04, 2018, 08:42:48 am
content: Quote from: timb on February 04, 2018, 01:37:45 amRC LiPo batteries are rated in 30C constant 50C burst and some even claim 50C constant. You can get 8Ah cells that are rated 50C. So thats 400A without parallel cells. Pro 700 size 3D heli motor can pull 3kW. They often use 2x6S in series (44V) to try and lower the amps and prevent melting wires etc.The pack will be depleted in a single 6 minute display. It will be almost too warm to touch and slightly puffed.Actually. Seems thing have moved on a little since I last looked...90C constant 6.6Ah = 594Amps. (Although 2S2P)https://hobbyking.com/en_us/graphene-6600mah-2s-hardcase-w-5mm-female-bullet-connector.html

author: Peabody
author_rank: Super Contributor
timestamp: February 04, 2018, 05:49:16 pm
content: I finished charging the lipo this morning. I connected it to my 18650 charger, which says it's output is 4.2V, 650mA. The lipo claims to be 1800mAh, but my guess is the 650mA is really something like 0.5C.The voltage across the lipo increased slowly, and I finally lost my courage when my cheap digital multimeter said it had reached 4.25V and the red LED on the charger was still on. The lipo measured 4.19V on my meter after terminating the charging.I think what I need to do is charge an 18650 while watching the voltage, and see where it is when the green LED comes on.There was no heat produced in the lipo that I could detect. But I don't know what protection is in the lipo, or in the charger. But if I plug in the charger with no cell in it, or connected to it, the green LED comes on. So I kinda assumed the charger wouldn't overcharge. But 4.25V is a bit much. The 18650s I have are protected. So I may try to get into the charger and see what's there.

author: paulca
author_rank: Super Contributor
timestamp: February 04, 2018, 06:20:11 pm
content: If it holds the 4.19V or close to it overnight it's a winner. Put it somewhere it won't set fire to stuff thoughWhen you aren't using it the LiPo will thank you for dropping it to around 3.8V

author: james_s
author_rank: Super Contributor
timestamp: February 04, 2018, 11:07:13 pm
content: Quote from: paulca on February 04, 2018, 08:42:48 amA lot of those C ratings are pulled out of thin air. I've seen LiPos that claimed C ratings so high that the discharge leads would burn out almost instantly. Any claims beyond about 40C continuous are highly suspect. A true 40C discharge would deplete the pack in under 2 minutes, 90C would mean the pack goes from full to dead in 30 seconds. If that were even possible it might work for a drag race but not much else.

author: paulca
author_rank: Super Contributor
timestamp: February 05, 2018, 08:20:21 am
content: Quote from: james_s on February 04, 2018, 11:07:13 pmYes. I have seen people doing speed trials with RC cars where they got one run from the battery. Probably binned it to afterwards. I think the record is around 200mph.I'm sure a lot of them are fictional. I accidentally shorted one through a mosfet load that went fully open when the sense line broke off. Luckily it was a little small one, 500mAh, but it was rated for 15C. The multi meter registered 16 Amps while screaming at me as it's 10A rated. Luckily I got every disconnected fast enough that I didn't blow the fuse or the LiPo. The LiPo was puffed and warm after only about 10 seconds.

author: james_s
author_rank: Super Contributor
timestamp: February 05, 2018, 09:20:14 pm
content: Some guys have done internal resistance tests and found many of the C ratings to be demonstrably false. I typically assume that a LiPo from a reputable brand is good for about half the stated C rating.

author: paulca
author_rank: Super Contributor
timestamp: February 05, 2018, 11:00:53 pm
content: I can test a few small ones, but I'm not testing a big oneThe 500mAh one for example has been through the wars a little. I can test if it will sustain a load of 15*0.5 = 7.5A. I recon it will.I know the 2200mAh 20C packs can sustain 200-300W@12V, so thats 17-25A, not really a challenge to the claimed 44A and I don't really have a load that will test it at 44A. That is of course the other problem. Testing them at those loads.The 30C sustained, 50C burst 5000mAh LiPo should be able to start my car. 250A burst. I could probably measure that, but it would require quite an interesting set up, probably involving copper pipe or welders wire as a sense resistor. How long could it sustain 150As without melting is more the question a 0.1Ohm resistor in a bucket of water can't possibly be sensible, can it?But Lipos producing enough burst current to start a car is not new, they sell them for that purpose in some devices.

author: Don Hills
author_rank: Regular Contributor
timestamp: February 06, 2018, 12:45:13 am
content: Quote from: paulca on February 05, 2018, 11:00:53 pmBig Clive did exactly that. Quite spectacular.