The Bms isn’t wired for discharge. Would you really put max regen at -20a per side? That would be going well beyond the cells charging limits.
So far so good. Just a little squeaking in the back probably from the cloud wheels. Other than that yeah, pretty good.
EDIT forgot about the thing when breaking when there’s no or very little power to the board. I don’t think that affects anything though.
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What if one cell or many cell groups is/are going low enough to trigger the soft cut or hard cut of the VESC, and/or those soft and hard cuts are set too high?
When under load a potentially compromised cell can drop a lot of voltage, and rebound back upto where it looks normal in relation to the other cells when the load is removed.
Cell balance in teh 3.8v range does not really mean all that much. its more telling in teh 4.18v range or when under 3v if any groups are out of whack with the others.
I am not saying the battery is junk, only that older cells have a higher chance of lesser performance, even from just calender aging
A 12mv delta is nothing, but it would mean more if that was at 4.19v or at 2.89v, instead of the middle of the discharge curve.
If the vesc settings are correct you’d need to be at the lower end of the charge for it to sag all the way through the soft cutoff into the hard cutoff. It definitely can happen, but in my experience only when the battery is on the lower end of the voltage to start with.
In regards to regen, it’s been discussed here many times, it’s very rare that you’re going to see that max regen current for any more than a fraction of a second, because as you brake and slow down, that battery current is going to drop exponentially. General consensus is that an extremely short burst of strong regen current is preferred over not having strong enough brakes
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In this scenario then yeah, it could sag all the way through to the hard cutoff but that battery looks healthy af
When I was riding today I had my bms app open trying to see how much it would sag and the most I saw was around 2v ish. I think that’s pretty good for a 2 yo battery but I could be wrong.
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Post up your hard and soft cutoff settings 
2v is fine considering how high you had those battery amps
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There at 40v and 36v. I have all my settings posted above with some minor changes.
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That’s pretty conservative for 12s and i’d recommend leaving them there.
If it happens again, your best bet for diagnosis without a logger is to print faults in your vesc tool app. Do you have a bluetooth module?
Even if you don’t, i believe you could leave the board turned on, connect it to the computer and print the faults through the vesc tool terminal.
As long as you don’t turn the board off, any recorded faults during the ride will show up
So what do you think the values should be?
The 35 amp max discharge is not a continuous discharge rating. It is the maximum amperage a healthy cell should be allowed to provide, and only as long as it is kept below the maximum temperature, which according to the datasheet you attached is only 60C, but I suspect the full datasheet would say 80C.
Some newer cells will have a pulse discharge rating and a duration of that pulse which is allowable, such as 120 amps for 3 seconds.
Mooch rates the P26A as a 25 amp cell, meaning that is the continuous amperage a single cell in free air can handle without exceeding 80C Discharging from 4.2 down to 2.5volts.
Inside a battery pack, inside an airtight enclosure the Continuous discharge ratings must be reduced, and as cells age their internal resistance goes up as well, meaning they will get hotter providing the same load for the same duration as they did when new.
But it looks like your battery is still healthy and your board’s issues lay elsewhere.
2 volts of sag is not much, if that BMS is actually capturing the actual sag and not averaging it over a period of time. I have no experience with Smart BMS and My Vesc attempts should be purged from my memory.
This battery had barely any cycles on it and was always stored around 3.5-3.6v/cell, so I’m sure it’s plenty healthy. Construction on it is excellent too.
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Good to know. Only thing that could go wrong with it is my wiring but I’m not too worried about that.
I’m so done with esk8. 2 dead batteries in the past year. Very tempted to just part out for cheap and be done with this.
Gimme a price for anything here plus shipping and it’s yours. I don’t think you would want the battery.
That looks a lot like a balance lead has come disconnected. I’d be willing to bet that battery is fine, just need to fix a balance wire
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