LiPo degredation
 

Due to an error on my part, two of our packs went way under voltage. No physical signs, but both seemed to loose some steam.

It could be that both my son and I noticed the same thing coincidentally. Or, does a single undervolt situation have that much of an impact on the pack?

1 pack is new, 1 has 10 race days on it so 50-60 cycles.

Trying to decide if I need to order new packs ASAP or if the damage will shorten their lifespan at the end?

How low are we talking here?

Chances are your pack is fine. Its only a placebo effect that you're feeling with your packs loosing steam since you and your son know the pack you are using were the one you "over discharged". Ive had this happen to me a number of times where I thought the packs I put in the car was charged, but ended up hitting voltage cutoff. My packs still runs fine, didnt puff up or anything and been running strong for almost 2 years.

One was down to under 2v per cell. Mine wasn't that low. I think my perceived issue had more to do with heat in the motor from a 7 minute main and then a second one (different batteries) after the next race. Maybe heat soak. Maybe ill handling cars as the handling went away in mine. IDK

It could be a bit degraded. I've done it before, and what worked for me was to charge it at a lower C rating ( I mean like .1-.5C) and then gently run it down to 3.7 per cell (don't go all out, just putt around or use a low amperage cycle mode on your charger) . Cycle them a few times and then ramp up to 1C charge and normal discharge, and be diligent with stopping when your timer rings (or cut a few minutes off for a few cycles). Then after a couple of those cycles, go back to normal. It should get it's pep back after that.

Of course, watch for puffing throughout those cycles.

Over-discharge just once like that may reduce life of the pack, but hard to say for sure by how much. It's kind of hit or miss, TBH. I have a 2s RX pack that I've been using in my air radio for about 10 years now and have discharged it to almost zero a couple of times. I know it's a low C RX pack, so that is a contributing factor, but this one pack seems to be really resilient. I had to cheat in order to revive this pack, though, as it was so low it would not register as a 2s LiPo when the charger does the pre-charge test. I've also had packs that I ran down to 3.3 and they puffed in under 10 cycles.

I can run a few more cycles through it though it's already been through a race day. At least they were cheap LiPo packs for a spec class and not an $80 stock pack.

2v per cell would totally do it. Theres a reason why basically all escs have a voltage cutoff. The battery chemistry is permanently damaged. It might not appear immediately but its definitely not the same. The lower you go the more risk. Some people say that its fine and it often is not much different than before or it puffs a lot quicker than others. Quick fixes are cycling slowly but it's not a real fix. Anything below 3.7v per cell is too low but not as bad especially if it was only for a short while, anything below 3v per cell is way too low.

It was totally accidental. Tried to increase the LVC and ended up reducing it inadvertently. Good times.

I would keep an eye on the IR of the cells and go from there, more info on how I track my IR here:
https://www.rcgroups.com/forums/show...0#post43510433

i would say they are damaged.
https://www.electricrcaircraftguy.co...ged-LiPos.html

Once you take a cell past 3.60 volts you do damage to it.. no way to rescue this.

If they have already seen a race day then no sense in doing anything else. Just use them and if they are not up to snuff for race day, just use them for practice and setup.

The slow cycling suggestions are for immediately after you realized you made a mistake. It happens, don't beat yourself up over it... we've all done it.

Live and learn. At least they were only $40 each. I'll pick up a couple and get back to burning tires.

Most ESCs default to a lower cutoff than that. You can safely go to at least 3.2V per cell before causing damage.

I believe hobbywings and other brands default to 3.5v per cell. Its debatable what causes damage to cells and to what extent but in general its agreed that below 3.6 per cell is not ideal and above 8v for long period is not good either, and the farther away you are, the more damage done. 3.2v is too low by then you've already done some damage, could be a lot could be a little but definitely not in the safe zone.

Just taking a quick survey of some of the ESCs I have lying around. Hobbywing XERUN XR10 Pro G2 uses 3.3V as the auto setting. Hobbywing XR10 Justock defaults to 3.2V per cell. LRP Flow Works team defaults to 3.2V per cell.