I stupidly left my battery monitors on my 4s HRB LIPOs while I was on vacation for a week and now two of the cells on all 8 of my packs are below 2Vs. I’m assuming my only option is to throw all 8 packs away and buy 8 more batteries. Anyone else ever make this mistake? Any other options besides tossing them or Frankensteining the 2 good cells from each pack to make 4 good packs?
Afaik there is no reliable way to wake them back up. They will always be a risk and need to be treated like charging or discharging will make them self destruct. Ive had little lipos just spontaneously puff and I don’t think i would trust them in my house. I have some ammo cans that i keep lipos in and i keep the cans on some scrap gypsum board in a fire safe area. With an inch of gyp board between them and everything else.
Maybe someone else can chime in on a good way to cut the bad cells out and weld on new leads. Isn’t there some issue like it’s an aluminum tab or something so it needs a beefy welder to pull it off or something?
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Any cells you want to use you need to charge as slow as possible as soon as possible. I think at least smaller LiPos have soldered series connections and you can take them apart.
anything below 2.5V is not worth keeping around. period.
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Yeah probably going to dispose of them at this point. 2 cells are at 3.7 V and the others were at 2V, and the 2V cells are climbing so the other cells are actively charging the cells. Sad that it’s $600 down the drain. I have them in a BAT-SAFE currently. Going to take them to the battery recycling center today.
They are probably ok, but you don’t know how much of that “okay” there’s left, as discharging them that low damages them, degrades capacity and can even result in internal short circuit. You can try to charge them in a safe way (in a bucket full of sand, outside) and if they go poof you at least have some fireworks. Beats just throwing them away. 
or a partial short circuit that gets worse over time as more dendrites slowly form from regular use
Not worth the risk.
Someone with battery building experience could disconnect the good cells from the bad ones and make 4 good packs, but depending on how the connections are done on the inside, it might require a beefier welder than most people in here have. So the chances of someone repairing it for you are pretty slim.
It’s probably just that they are partially recovering slowly after you removed the load from them. The good cells can’t put their energy into the bad cells. They are just connected to them in series. No need to worry about this.
Just don’t manually connect the pack or the bad cells to a charger.