T i m wrote:
On Tue, 17 Nov 2020 12:13:56 GMT, Pamela
wrote:
Surely that has been incorrectly taken from the standard advice to
slow charge a new battery for a long time (say 8 hours) to ensure
all cells reach max charge. Hard to see why it's applied to single
cells.

Same thing though isn't it Pamela? A battery only (typically) being a
combination of single cells wired in series and so the current though
the battery = the current though each cell?

Yes and no. NiMH cells can tolerate a certain amount of overcharge without
damage - they just turn it into heat. In a pack, you aren't monitoring the
cell voltages (like you would in lithium ion) so you're applying a current
and hoping the cells take charge equally (ie that current x their cell
voltage is the amount of power they're taking) until you reach charge
termination of the whole pack. If the current is low, it doesn't matter if
cell A is fully charged and burns it off as heat while cell B is still
charging. But if it's higher the risk is cell A overcooks before B has
finished.

If you're charging a single cell you know charge termination is for that
cell alone and so you can run a higher current and still detect it
correctly.

Theo