Battery Vehicle Society

Well, after two nights of charger puffing and blowing, my cells are finally getting balanced :D I had the load cutin voltage set at 3.40 volts and when I checked this morning they were all round about this level (and most of the loads were on), and after settling the pack showed a nice healthy 85V :...

I haven't really had the time lately to do any more investigation on this cell problem, but I've now modified my charging code so that instead of one cell hitting the preset max voltage and finishing the charging process, it now just stops charging, waits for the high cell to be pulled back down by ...

I was going to say I don't really have any control over or way of testing individual cells' states of charge, but I also presumed that paired cells balance themselves anyway if they're healthy?

I had thought about possible variation in batches, the new cells I bought are visibly different from the old ones, the negative end is silver in colour instead of black. Given that there may not have been anything wrong with the original cells I'm now thinking of putting the other old one back in an...

As an update, I'm still getting strange behaviour on that cell. The scooter is rideable now but that cell still dips to 3V or so under acceleration, and still causes the charge to cut off prematurely. It's really annoying because I can never get the cells balanced now, I'm lucky if I get a "ful...

Swapped that cell last night, and although it still dips it's not as bad as it was, so I may have to live with it. It still charges quickly so maybe if I can get a better balance in the pack over time it won't be such a problem. I hope

Yikes! That looks a little more complicated that I expected :shock: However, I had a sudden brainwave last night on what's happened. I realised that my reconnection "fireworks" only involved one cell in my new cell pair. I reckon that took it out so that pair is now running on half capacit...

Well I think I can rule out the BMS - I tested the voltage at rest and charging (as I said, pretty difficult to test under load :) ) last night and it pretty much matches to within 20mV (which is obviously the resolution of the BMS anyway). I also swapped the PIC with its neighbour to rule out any i...

I'm beginning to suspect the BMS/wiring even more now as the problem is still there (although not as extreme as before). Under load, cell 5 drops to <3.00V (even though it was the one that triggered a charger stop on Saturday when I last charged it). Any clues where the problem might lie? I'm thinki...

It would be interesting to do a capacity test on the old cells. One of my projects is a battery/cell cycler that will safely charge and discharge cells and report the capacity Now that sounds interesting - I wanted to test the cells anyway because they may be fine, but battery testers seem to be pr...