I went for broke...
Almost. It was taking too long to hit my goal of 50V, so I chickened out at 66.
0.6Vx120 cells = 72v. 0.4Vx120 =48v. Numbers given by "battery university" regarding nickel cell reconditioning. 0.6v being the minimum to have an effect from one quoted source, 0.4v being suggested by another source as the goal.
The problem there being that only works if you are doing single cells, or by some miracle, they all stay in balance...which is basically impossible.
It all might be a load of BS, but I did read "50V" being the absolute maximum one seemingly informed user posted on insight central.
Watched a youtube video where one guy had "great results" from driving his pack don to 0v, which he did once or twice a year and had supposedly put 100k on his supposedly "bad" pack by doing this. He seemed
very un-informed, though. Absolutely no research or science behind his choices. But at least, if he wasn't lying, it suggested that the pack won't go belly up if you "accidentally" discharge it too low.
It's all about the cells being balanced, because unbalanced cells means they will - reportedly, from many sites - go in to "cell reversal", where they literally flip polarity and can/will be damaged irreversibly. Hence why I took several discharge/charge cycles before going for an even deeper discharge. The idea was to revive and, hopefully, balance as many cells as possible first. Otherwise the weakest cells would have gone deep in to reversal.
In theory, the worst cells should have been the first ones to drop low and then be reconditioned. Which means on the second cycle, they would
not be the weakest (they could have, in face, been the strongest, if they weren't actually damaged). So a second group of cells would have been the first to bottom out and get reconditioned on the second cycle. And again on the third.
The deep discharge was, realistically, to catch the cells that were the most healthy to begin with, so that all cells would be reconditioned at the end of it. Not having gone all the way down to 48v means I could have missed some...but then again, if they were that healthy, they probably didn't need reconditioning.
Take all this with a grain of salt. It's what made sense to me to do, while minimizing risk....at least without actually pulling the pack out and reconditioning each stick individually. That would be the best/safest way. I don't see much point in going through all that effort though, unless the pack can show me it's got enough life in it to be worth it.
Considering I bought it assuming the pack was toast, I wasn't counting on being able to revive it.
Considering even if I went through all that effort, it would probably still be a turd - it's not going to come back to 100% capacity, no matter what I do - it wouldn't be worth my time.
Hence, I went with an approach that I expect would prevent making it
worse than it already was, without wasting unnecessary effort. I was in no rush while i was waiting on parts, after all, and I have other vehicles. A week of charge/discharge cycles where the most effort I put in was in modifying the charge cord seems right up my lazy alley.
I could have assumed it was never going to revive, at all, and just tanked it right down to 0 volts the first try...reversing most of the cells in the process. Not how I do things.
22 hours in:
Highest voltage I've seen yet. Fingers crossed, that's a good thing. The highest I've seen it previously is 172, which quickly settled to 170...as this chemistry of battery drop 0.05v once they hit 100% SOC. I think 176 is the max a healthy pack will hit...
I'll find out if it was worth even this much bother later...haven't hit 24 hours charge yet, haven't fixed the leaky roof/pillar seals and it's decided to piss down rain this morning...might just wait until tomorrow. Might let it keep charging until the voltage it settles.
I'd be chewing my nails in anticipation if I was more excitable by nature.
