I’ve been charging up the pack today and it seems to be working. The balancing is working and the cell’s resistance seems to be reducing so I think I may be able to save this battery after all.
I’d be scared to use it again. What would you rather fork out for a new pack or a new board? I’m going to try and fix my pack and just use it for low power applications, maybe a portable charger
You haven’t saved it. Its going to gradually shit on you completely no matter what you do. I did the same thing with some 2s lipos. Had one of them drop and it started taking out the others. Originally bought 6 2s for the build and ended up having to buy 4 more to replace the dying ones. Don’t compromise your other lipos! Replace it.
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I know he’s using a lipo. His cells are basically brand new, yours probably are not. The battery is not trash.
I do this for a living plus I also fly a lot of RC and have over discharged plenty of batteries when I forget to set my timer. If its an older battery it’ll get puffy and capacity will be greatly diminished and you can essentially call it trash. On a newer battery you’ll probably lose 20-30 cycles of life plus some capacity which isn’t insignificant but the batteries are definitely not trash.
If he takes better care of them, he’ll be okay. The battery isn’t 100% anymore but its also not super damaged.
@J0ker3366 Not two scenarios are the same. You had 6 different batteries to keep in check. He only has 2. Yes, eventually the lipo is going to crap out, all of them do. His battery being brand new and only over discharged twice now, (I hope) wont ride as good as it would had he never over discharged them but again, they are not trash.
He’s also got a balance charger, so he can learn how to use one properly and how to diagnose a dying lipo. With his charger he might even be able to do a capacity check, IR check, and temp check on a charge cycle, all of which can determine the state of his battery far more accurately than any of our guesses.
Doing a periodic capacity check on your cells is recommended so you don’t get caught off guard when a battery starts dying.
Yes, one bad lipo can take out other good ones but with the proper care, it won’t happen. If he follows my advice and raises his threshold so that none of his cells get over discharged any more he’ll be okay.
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Some general advice to help you get caught up quicker.
If you’re running without discharge bms, especially lipo. Don’t even get near the neighborhood of empty. Things get unpredictable near empty, especially with old or damaged lipos.
Check cell voltages of old or suspicious packs often.
Lipos have different “empty” voltage than 18650. About 3.7v is essentially empty. 3.85v is about 50%. Sounds like your battery meter, and your vesc settings, were for lithium ion not lipo.
Don’t leave lipos at full charge for long periods.
With lipo, you can plan your rides so you charge to full right before the ride, and finsh the ride at storage voltage, you can save from over discharge problems and a lot of fussing with storage charge.
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Thanks @PXSS. I’ve taken the batteries to storage levels which seemed to have balanced everything nicely again.
I cant do a capacity check with my charger, unfortunately. Can you suggest how I would do this? I’m also not sure what and IR check is?
Cheers and thanks for all the great help!
What charger do you have?
I’ve got the Graupner Ultramat 18 from Trampa. It can charge up to 12s, which allows me to keep the batteries in the battery box and just plug the charger into the xt90 sticking out the box.
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Update:
when I woke up this morning and went to charge the batteries for a morning skate, I saw that the one battery hadn’t retained the storage charge very well compared to the other. I didn’t jot down the voltages before I started charging, but I took pics just after charging had started, which should still show what I mean.
I’m going to ride it a bit after its charged and then check the levels afterwards to see how unevenly the draw is. I’ll post the results after that.
Everything was configured for LiPo. I got the board from Trampa, pre-built, and they advise the VESC configuration for LiPo, which I set accordingly.
Here are the settings that were sent to me when I first bought the VESC. These are for a single motor configuration.
Motor Current Max:
118Kv: up to 45Amps
136Kv: up to 50Amps (my motor size)
154Kv: up to 55Amps
Motor Current Max Brake: up to -35Amps (will give you efficient braking not too sharp)
Battery Current Max: 60Amps
Battery Current Max Regen: -30A
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This is what I was talking about with respect to vesc. 3.2v cut off per cell is low for lipo, especially with no bms on discharge.
sidenote: Even with BMS you don’t want to bump into low cell voltage cutoff and have the bms cut power.
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Do you use the balance lead when charging? Or do you use a bms in the box, if you don’t use balance leads the cells can’t be balance correctly
Definitely! The first thing you read about LiPos is how you need to ensure they’re balanced.
All g, I thought you weren’t by the way you said this
I thought I’d share my individual cell volt readings from yesterday to get some thoughts from the forum.
(I started tracking my voltages in a spreadsheet instead of just as pictures, to make it easier to share here.)
Below is a table of what the readings looked like:
| Description | Cell 1 | Cell 2 | Cell 3 | Cell 4 | Cell 5 | Cell 6 | Cell 7 | Cell 8 | Cell 9 | Cell 10 | Cell 11 | Cell 12 | Total Volts |
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Fully Charged for the day | 4,190 | 4,194 | 4,191 | 4,196 | 4,195 | 4,194 | 4,195 | 4,195 | 4,194 | 4,194 | 4,195 | 4,193 | 50,326 |
| After first skate | 4,077 | 4,067 | 4,100 | 4,033 | 4,127 | 4,081 | 4,094 | 4,094 | 4,094 | 4,089 | 4,095 | 4,094 | 49,045 |
| After second skate | 3,919 | 3,909 | 3,943 | 3,891 | 3,962 | 3,926 | 3,939 | 3,939 | 3,937 | 3,932 | 3,938 | 3,937 | 47,172 |
| After final skate | 3,729 | 3,719 | 3,741 | 3,706 | 3,752 | 3,731 | 3,742 | 3,742 | 3,737 | 3,739 | 3,735 | 3,737 | 44,810 |
You can see that cells 1-6 don’t discharge as evenly as cells 7-12. I’m not sure exactly how bad it is, as I’m not sure what the tolerance should be.
I’ve had no heating up or puffiness of the batteries and the batteries seem to be performing well.
The difference is less than 0.1V. I wouldn´t worry in this case. Just keep tracking the values in future. All your cells will have probably a slightly different internal resistance, so over the discharge they also slightly discharge different from each other.
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Thanks Andy. I’m glad my batteries don’t seem to be ruined.
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Sorry I havent replied. The thread wasnt pinging me. I’ll give you a more detailed reply tonight but your cells look good on a quick glance. Yes they are not as even on 1-6 but that’s expected after the over discharge.
I’m glad its not damaged too bad. Keep checking it regularly and it’ll last a long time 
Do change your vesc settings as @deucesdown recommended!
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A little off topic, but the cells I over discharged came back up to 3.98v after letting them rest for a day or two. I then charged them at 1 amp to 3.4v then 3.5amps up to 3.75. The cells seem almost unscathed as they perfectly balanced themselves without even using the bms or anything, just connected straight to the output of a hobby charger with two battery cell checkers connected.
I still plan to put a new pack into my board as I am paranoid about an esk8 fire, but I guess you were right about the cells being salvageable. They will now be a power bank for my phone and esk8 range extender
I would never recommend using a battery that was not balance charged immediately after an over discharge event. They might look ok but they need to get balanced at 4.2v. So unless you have a way to balance charge them, yes, you should replace them.
Also. Dont let your lipos rest too long after an over discharge, it’s not good for them. The sooner you get it to its storage voltage, the better. You do have to keep the battery cool though.