parallel charging and cell balance

[Willyuk]

your views welcomed​​I have been parallel charging my 5s lipos for some time now and have a question for the experts about how the cells are balanced across the packs. EG. I charge 4 5 cell lipos, the charger only sees 5 cells, so all 4 cell number 1 are seen as one cell. The charger then balances between the 5 cells in the "pack". So it must average out the 4 number 1 cells, the 4 number 2 cells and so on. I have noticed that when looked at as one large pack, it shows all cells as equal but when I check each individual pack each cell is different across all of the packs, i.e I have 20 cells at slightly different voltages. Add them all up and they are balanced. Is this a problem?? Recently I have been parallel charging to 4.15 volts and then finishing the charge for each pack separately so that they all end up at bang on 4.2. Is it worth the effort or does a minor variation matter in terms of longevity etc.

[MattyB]

Just charge them singly every now and then (every 5-10 cycles) and you should be fine. However you should always check the cell voltages individually before you begin parallel charging to make sure you are not starting from a position where one or more cells in any pack is dramatically different to the rest. If it is, balance charge that pack singly at 0.5-1C to vice it a good shot at getting back into balance.

[Willyuk]

Thanks Matty, i thought the slight variations was not significant but they do seem to get worse over a period of time and also the IR raises a bit, one cycle on my PL6 seems to even everything out again.