New Lipo accidentally discharged to 2.6V

[rg12]

Hey guys,

My friend bought 3 7S 16Ah 25C LiPo packs and has no cut off in the controller (Chinese one set for 41V) so on the first ride he wasn't used to the low distance he gets since he runs about 120A and he discharged the packs to 2.6V per cell and the cells got slightly puffy (only a bit).
I never seen that on a new pack and is 2.6V really a LiPo killer?
Anyway I told him to immediately charge it and be next to it all the time and now it's back to normal voltage and suprisingly everything was perfectly balanced.

Question is, do you thing it did any harm to the packs from one time dropping to 2.6V?
I guess if it was settled at 2.6V that under load it was alot more so...

[skeetab5780]

Oh ya they are ruined! It only takes one time. They may work for the next 5 years but they will never be 100% again. Be careful

Anything below 3.5v on lipo is bad, especially pumping 120a

[SirLongAss]

I recommend putting somewhere outside and away from anything you don't wish to part with if you plan on charging it. 2.6v is salvageable if you can set a lipo charger to trickle charge it at 0.1A until it gets to 3.2v.

I perfer just to overcharge it until it explodes

[rg12]

Yesterday had a ride with that friend and the left side of his frame open and everything looks good, performance is insane (nasty acceleration...)
Does it really take one time while they are brand new to damage them?

[SirLongAss]

Yesterday had a ride with that friend and the left side of his frame open and everything looks good, performance is insane (nasty acceleration...)
Does it really take one time while they are brand new to damage them?

I can not stress this enough, yes! However, the battery is above 2.5v so the risk is minimal.

On the odd chance, a hair of lithum metal can build up between the anode and cathoide after a number of charge cycles and cause the battery to short.

[rg12]

Holy shiz...

Yesterday I the guy added that he got to cut off while the controller's cut off is 40V!
meaning that they settled at 2.6V but the sag to get to 40V means 1.9V

[SirLongAss]

Holy shiz...

Yesterday I the guy added that he got to cut off while the controller's cut off is 40V!
meaning that they settled at 2.6V but the sag to get to 40V means 1.9V

Just worry about the idle voltage.

I just noticed you said the cells had puffed. You're friend should depose of them. The puffing is already an indication that the metal lithium is building on the thermals. Even charging outside, the damn things could go off on between you're friends legs while driving.

Maybe have a way of quick ejecting the batteries if they start to burn off.

[Alan B]

The puffing is a sign that some gas was released.

I have some LiFePO4 that puffed years ago. They still seem to work fine. Different chemistry, do we know what for a fact happens with this chemistry when this situation occurs?

The safest thing is of course to start over. Anything else is an experiment.