Trickling that dead pack up with a small charger, maybe putting an amp or so into them over many hours to slowly bring the voltage up should be about the safest way to do it. When i rezzed an 8 kw dead pack I hit it with 1.5 amps for about 6 hours to get them to a voltage the BMS would say ok, I see batteries again. At that point still, do a very slow charge up to full cap.
At this point check each cell as you can, to see if any balancing needs to be done, if so, do it. Let it set about 2 or 3 days, then check the cell voltages again, see if any drifted significantly. This will tell you if you got on that is bleeding internally and likely to cause a catastrophic event.
From here Id do a controlled discharge at a medium rate down to rated cut out voltage of say 20 percent charge left. From here, check cells see how they fare, any significantly higher or lower ones in the series is telling of bad players, that again, can cause you great grief.
From here charge back up at about a 0.5 C rate. This is fast enough that it will generate some heat to see if they ARE still good, but without just daring them to super nova on you! Hit full charge, check cell balance again, yes check it again, you are cycling them fully because any cells that are significantly degraded capacity wise will quickly take down the pack and force others into a critical point. Critical Event for LiPo's tend to be extremely thermal. ie a bad day and pissy neighbors when that cloud of acrid smoke wafts into their windows.
if they behaved to this point, the pack should still be good to use.
Also, as a general comment: When LiPo's Do decide to give up the ghost, often you have very little notice. By the time it's swelling, it's often too late, if it's smoking, IF IT IS SAFE, get your insulated pliers and cut that sob out of the pack if you can!! AT least cut the power cables to try to keep it from causing a sympathetic ignition of the other packs (this is assuming it don't rupture and spew flames right at them, in which case you are just #$$ked). If you see them puff and hiss, often you have very few seconds to react.
and whatEVER happens, and this pisses me off the most because god damned fire departments should KNOW BETTER, They have been trained supposedly......
DO NOT POUR WATER ON A FKN LITHIUM FIRE, IT DOES NOT PUT IT OUT, IT CATALYZES IT !!!!!.....ok ok fine, the chemists out there are going to scold me, fine, whatever, it's more of a reagent but the point stands it makes the fire much WORSE !!!
Disclaimer: I have been playing with electricity and batteries for over 40 years. I am comfortable doing the things I told you but do know that they can be very DANGEROUS, especially if you are not savvy to the way this stuff behaves, or are shy about electric. If you don't like the way it sounds, then please don't do it, but if you are confident... here are some possible tips.
Good luck and if you want to reach out in DM's please feel free. I know that some probably would not want me to continue on THIS path on a public forum.
Aaron
Author
Topic: Yet Another Dead battery... but hoefully not (Read 817 times)