Just to add, it's sometimes cheaper to buy a different make of
battery that may be on offer and rob it of its cells to fix another.

This is not generally a good idea. Replacing the bad cells in one battery
with new, good cells, is likely to cause cell reversal during operation.
You
should generally replace all the cells.

I think that's what he means. Rob one (unusable brand) battery to
replace the cells of your (wanted brand) battery. As long as the cells
themselves are the same, it's all good.

Perhaps. But the principle stands -- replace all the cells.


It's also useful to have some way of measuring each cell's capacity
while discharging it, so you can roughly match the cells' capacities.

The cells are sometimes stamped, if not, you can get a clue from the
label of the battery case (the outside plastic case). They may not give
you too much information other than the brand and model, but they
usually do state the Ampere/hour capacity.

It's ampere-hour, not Ampere/hour. Big, big difference.

Cells with the same mAh rating from the same company nevertheless vary in
capacity. I've had to return new cells for replacement because they were way
out of spec.