How to Revive a Dead battery that was sitting for a couple years

[MarkJohnston]

My little brother has a battery and we want to revive it. His bike was stolen at work, he took the battery inside with him, thief did not get battery. He has left the battery sitting in his room for years and now it is dead. It's a 54.6 volt battery 10.5 A. IT is 13s3P I believe. The voltage is super low as he neglected to charge it. The battery no longer will charge with the charger. However I am hoping that perhaps the BMS drained the battery. Usually the BMS is only hooked up to the one of the cells groups.

I have seen instructionals online before that if I cut open the battery and located the dead cell group and put it on a TRICKLE CHARGER (100 mA) that I can revive the dead cell group just enough to enable charging to happen. IT was stated that this is a trick to trick the BMS. They used a bench power supply, I however DO NOT have a bench power supply, but I did just buy this off ebay! WIll this work? I do not want to have to spend $400 for a bench power supply (I will not cheap out on one for this! I will wait till I save enough for the BIG guns! No budget BPS for me!) This little driver has constant current and voltage! How about I use this outside to get the job done?

5A DC-DC Constant Current Voltage Regulator Buck Step Down Converter 4-38V | eBay

Output current: Max. 5A (adjustable). Therefore, the battery must be used at the beginning. Use as a high-power LED constant current driver module. Short circuit protection: Yes (limited current 8A).

www.ebay.com

Also what if we wait any longer to do this? WIll the voltage get so low that we can no longer try and revive the pack?

 

[fechter]

I've revived many batteries that were below 2v by slow charging to above 3v, then using a normal charge current. I have not had any issues, but as mentioned above, bad things can happen inside the cells when they get below 2v and there will be an increased risk of fire when charging. Charge in a fire safe location. Check the voltage on all the cell groups and try to get them balanced as much as possible.

 

[MarkJohnston]

Ok opened it up and it looks like two cell groups are at 100mV. That is what done it. This on the end that is hooked up to the positive terminal. The BMS appears to run the negative terminal of the battery through it. There is No LED indicator to indicate that this has integrated charging circuit. I am pretty sure the BMS has drained it over time.

I don't believe there is any way of further isolating the cells? They are all spot welded together. What a shame this battery looks very well made. Well not sure if I should try trickle charging those two groups? Or should I disconnect the BMS and when I get a chance I should take apart the battery salvaging the cell groups above 4.0 V?

Should I try trickle charging and monitor the battery for heat? Please advice.

 

[calab]

Slow charge at 0.1 amp and baby sit.

 

[fechter]

If you only have two low groups it won't be too hard to try it. The slow charge part is pretty safe. Once you get all the cells into the healthy range, you can use normal charging current. It might take a long time to get the all the way up.

 

[MarkJohnston]

Ok will begin experimentation with the trickle charger tomorrow. I will first see if I can get a couple of old individual cells up to 3.0 with the trickle charger, and then move on to the bigger battery. I am setting up a large outside area with cinder blocks. I have lots and lots of cinder blocks and bricks. I also have a large sandpit area far away from any trees or wood. I will have a fire extinguisher and several pals of water on site.

I will monitor the batteries for heat and if they get too hot I will take them off the charge. I just hope it doesn't start smoking or eject very far hot pieces of plastic/metal/battery peices/etc.

 

[MarkJohnston]

Ok there may be a problem with this charger. I used a single 18650 cell to test it. This cell was sitting at 970 mV. I set that charger to 3.5 V and 90 mA. I plugged it in and immediately it charged the battery up to 2.5 V! And now it is trickle charging slowly now. Why did it jump so fast? Perhaps it was just a bad cell? But the cell is not very hot at all, barely warm. Maybe I shouldn't trust this with a larger battery...


P.S. I have individual 1V 18650 also trying to revive.
Yeah the cell is just warm, not cool or hot. Is that ok? I have it charging at 1 amp. I think I want to bump that up to 1.5 amp from now on. Charging at 50 mA takes forever. I have a lot of batteries I am reviving ATM.

 

[fechter]

The initial fast rise is to be expected. It's not really charging until it gets to a bit higher voltage. At higher "revival currents" the chances of something bad happening go up. If the outside of the cell is warm, something inside could possibly be quite hot. Hopefully that's not the case. I usually try to get them above 3.0v before going to a normal charge rate. 2.7v might be high enough. If you have a group of low cells in parallel, charge them all at the same time in parallel.

 

[MarkJohnston]

Right It's just a pain, but I am doing it. I start out at 2.2 V and charge at 50 mA. Once it reaches 2.2V I switch to 3.7 V and 1.5 mA. I just tested with an Ammeter. The current is flowing out at 86mA to begin with when I set it to 86 mA. That is correct. however it reaches 2V VERY QUICKLY. I am wondering how this is possible? It happens in about 30 seconds. Once it hits 2V or so, it then starts trickle charging, voltage barely changes.

Makes me wonder if I can get away with setting it at 1.5A at the beginning. right now I am just testing old bad cells I've been meaning to revive from another pack I took apart a long time ago. I have seen videos on YouTube of people bump charging single 18650 cells with no resistors.

The thing is a pain to adjust no wonder people do this with bench power supplies. Thankfully I don't have many more batteries to do.

The battery gets just a little warm. Nothing even close to hot. And it does that even when the trickle charge 86mA and low voltage are hooked up. Honestly it might even just be me.

I am still thinking about attempting the larger pack. yes it is 13S3P. I have isolated the bad cell groups. I really don't want that thing to burn.

Ok thank you. I think I can use my powerful Strong Neodymium magnet to magnetize a long peice of metal to link the rest in parallel and then for the + terms is easy. I can find wire to stick in there. This should save time. That is good. So that will be about 5 dead cells all at 1V or a little less, all hooked up in parralel on the trickle charge. Excellent. Would this though mean that the cells are out of balance ? I guess it won't matter if it's individual cells however I would like to have these cells set up and ready when I do eventually want to pull them out of storage to do a build/and/or sell them if possible. I want to use this charger above to bring these all to 3.7V and of course all of them having the same capacity.

 

[fechter]

Any cells below about 3.0v are fully discharged and should not be a problem to connect in parallel. At 86mA, there isn't enough power going into the cell to heat up anything so should be fairly safe. Bringing a cell from near zero to 2.5v doesn't involve any of the charging reactions, so this can happen quickly. This is normal.

When cells get below 2.0v, some of the copper can start dissolving and when you charge it, the copper plates onto whatever is nearby, possibly causing a short. I think most of it plates back onto wherever it came from, but there is no guarantee. How much copper is dissolved depends on a lot of variables, like how long it stayed dead, temperature, what voltage, cell construction, etc.

 

[MarkJohnston]

Ok. The ones I sis last night have held their charge overnight. I guess I will do the rest. I even have an a power bank I am restoring.

 

[MarkJohnston]

Shit! I messed up with the BMS and bridged the FD and CD CIRCUIT! Did I break the BMS? ANYWAY to test the BMS? Before and after pics attached.

ALSO, the LI ion charger I bought AGAIN did not come with the specified voltage! Its suppose yo be 12.6 V but is instead 12.74 volts. Spread across 3 cells in series that amounts to 4.24 ~ per cell. Is this dangerous? I've been checking a lot of my chargers, NONE of them see to at spec, either above or below. Will the overcharge protection on my BMS protect me?

 

[fechter]

Not sure what FD and CD are.
4.24v may be OK for a test but you wouldn't want it that high all the time. Some chargers have a voltage adjustment pot inside.
Also, make sure your voltmeter battery is good. A low battery can cause inaccurate readings.

 

[lifepo4ever42]

i guess 18650 are better to recover, but if it was lipo or lifepo4 forget about it

 

[MarkJohnston]

Not sure what FD and CD are.
4.24v may be OK for a test but you wouldn't want it that high all the time. Some chargers have a voltage adjustment pot inside.
Also, make sure your voltmeter battery is good. A low battery can cause inaccurate readings.

FD and CD are places you can test during charging I guess. One is full charge and other is while currently charging. Perhaps one is not always on.

I can't take apart charger easily. The volt meter should be correct. I tested with my other one too. Same reading

I'm going to ask for a free charger from ali

 

[fechter]

Try that first I guess.
A crude way to lower the voltage is to place a diode in series with the output. A regular silicon diode will drop about 0.7v depending upon current. That would be too much to get full charge though. A Schottky diode will drop a little less and might be in a good range.

 

[MarkJohnston]

I found a diode on this charger I took apart. I guess I'll give that a shot. Maybe the seller will send me a new charger for free, or perhaps I'll just do this crude method...

So in order for this to work I need to put this in series with the output? So just run the positive of my battery BMS terminal through the diode? And then the other end of the diode will run to the positive of the charging port? How much will this little diode drop the voltage? I am really in tight tolerances for this application. I pretty much need the 12.6 Volts because I am drawing 800 mA @ 12V. I know I should probably have built this as 4S2P and bucked down the voltage more. Sorry I know this is a bit off topic, and thank you for helping me.

 

[From-A-To-B]

There’s not much energy in a cell between 0.1V and 2.0V, and the voltage jump you see is a little bit like voltage sage happening in reverse. The cells are trying to soak up the 2V+ you’re feeding them, and the voltage rise happens very quickly.

I’m reluctant to resuscitate cells under 2V, and would just forget about cells at 0.1V. They may charge up for you initially, but are almost guaranteed to have a lower capacity and higher IR, leading to pack imbalances and heat from those groups in the future. The cell structure is physically impaired when discharged that low (per Fetcher’s explanation, and I’d consider the cell bunk.)

I’d just replace those cells groups, if you have a spot welder, or at the very least keep a super close eye on it and store in a safe location.

FWIW: many people use 5V cell phone chargers to bring up low cell groups and balance batteries. You can find these in 200ma output variations. But you have to watch the process because 5V is far too high of an ending voltage and 200ma is too high of an output to trickle charge cells under 2.0V, IMO.

Good luck, have fun, be safe.

i guess 18650 are better to recover, but if it was lipo or lifepo4 forget about it

Not at 0.1V levels. Pouch cells would swell when discharged those low. Cylindrical don’t swell because they’re stuffed into a can, but the same damaged has occurred internally. It’s easier to have a false sense of security because there are no visible changes in the cell.

 

[fechter]

With that diode, the voltage will probably drop to about 12.0v with your charger. You can at least charge partially without worrying about going too high. The diode will get pretty warm too, but should be OK for 800mA.

 

[MarkJohnston]

With that diode, the voltage will probably drop to about 12.0v with your charger. You can at least charge partially without worrying about going too high. The diode will get pretty warm too, but should be OK for 800mA.

Ok there are are smaller diodes on the bread board too. I will get a different one

 

[MarkJohnston]

From-A-To-B​

When you say " store " in a safe location, does that mean its possible the battery could explode just sitting there with no charger connected and no discharge ? I do keep the batteries in a cool dry place....

 

[MarkJohnston]

The diode trick didn't work. I used a smaller diode and ran it in series with the charger. The charger said 12.45 volts. It's gone down from 12.7volts. But in practice after charging for a couple minutes it cut off the charge at 12.00 volts...Hopefully the charger isn't broken... Why won't it charge up to 12.45? perhaps the BMS won't let the battery charge beyond a certain point? I am doing independent research on this diode charger thing as we speak.

I am discharging the battery right now for testing purposes. I have it hooked up to some cells in parallel I am restoring. IT is discharging and not cutting off the discharge. SO I don't believe the BMS is broken because charge and discharge share same port. I have shorted out the battery many times because I only have large clunky tools and I get frustrated easy, I don't have the most steady hands. On circuit boards everthing is so close together, it's easy to arch too, I hope I haven't broken the BMS or the charger, again I say that.

I am about to just buy an IMAX B6 and say screw this charger and BMS.

P.S. The diode thing is super confusing too, because current can only flow one way. I guess that when using the resistance setting on the meter you can tell which side is which because the wrong way will generate OL or infinite restistance, and the other way should give a number betwenn 1000 ohm and 10 ohm, something like that. But I'd figure that me hooking it up and seeing the voltage on the end of the charger with my meter, that should be the correct way. But when the diode was connected to the circuit board, I could run current through it both ways, very strange.

 

[fechter]

You can measure the voltage across the diode when charging to see how much voltage drop you're getting.
Some meters have a diode check function that is nice. Using an ohmmeter can give you goofy readings as you have found out.
With the diode in series, the voltage reaching the pack would be around 12v. If there is enough charge on the cells, the current may be low enough to trigger the end of charge cutoff.
You could just use the full 12.74v and babysit the end of charge to manually turn it off when it reaches 12.6v.

 

[MarkJohnston]

You could just use the full 12.74v and babysit the end of charge to manually turn it off when it reaches 12.6v.

No way. I could set up a mechanical outdoor timer though that cuts off at a certain time. But first I need to know how long it takes to charge the battery. Pretty sure I screwed up here, because the LED this is going to power only works at 12V and draws 800mA. I hope this 3s2p battery is going to be able to provide the voltage for a while, otherwise light will go dim pretty quick.

Nothing can be done now, except hope this works. There is no more space for another cell in series or parallel in the custom case I designed. Also BMS is designed for 3s...., dont think BMS can be hacked for less or more cells in series?

 

[MarkJohnston]

So far I haven't been able to get the charger to charge past 4.225 volts. This is without diode. The diode actually snapped off, these diodes are flimsy and not meant for mechanical stress in line with a charger cable. Maybe I can cut off a peice of circuit board(can you get cancer dremeling apart circuit boards? guts tell me so), and do it that way... But still I have not be able to charge battery to 12.74. I just charged to 12.68 and then unplugged the battery. I then came back two hours later and plugged it back into charger. I left it on charger for two more hours. I came back and tested. It's now at 12.63! So it dropped some voltage! I can feel the heat sink on the BMS warming up, what kind of BMS has a heatsink anyways? Is this the 'overcharge protection' spoken of in the manual?

This is all making me wonder... If this charger is so cheap I wonder if it's even a designated Li ION adapter? I have other chargers one was for a router not a lithium ion product by any means. That charger will only charge at 1.5 amps and is 12.3 volts, so no danger of overvolting there.

I did get a refund for this crappy charger of $5 whopping bucks. Lol. seller was pretty mad, but I tested with two different meters and got... the exact same reading. Don't think it's the meter low on batteries unless both meters are exactly the same low on batteries, and both gave the same exact reading...

should I try the other charger....? or is a 1/4 volt over 4.2 super dangerous? I don't give a crap about the life span, I have plenty of cells, I can just keep making this same battery over and over and over.

I don't feel like baby sitting the charger all the time, it's annoying...