"who where"
"Wild_Bill"


I don't presume to know.. internal resistance is a factor, maybe not the
most critical, but a parameter that could be useful. As I've said, I
believe
ESR/IR is more useful than a simple battery test meter.
As the cell's IR increases, it's capacity drops, from what I've read.

No. Note TWO relationships: (1) Internal resistance will have an
effect on the usable capacity, in that it will result in earlier
discharge termination at the terminal voltage will droop more under
load. (2) As the cell's usable capacity reduces due to "wear and
tear", the internal resistance will usually rise for similar reasons.
But IR is NOT the cause of reduced capacity.

** Bill's post does not say it was - only that there is a correlation.

There is a strong correlation between measured ESR and state of charge for
non-rechargeable cells - but it is only when a NiCd or NiMH cell is almost
completely discharged that the ESR rises.

The whole idea is that ESR testing is a COMPARATIVE measurement applied to
a *number of cells* that are of the same type and with a similar history to
see if any show higher readings than the others.

It is also useful to apply ESR testing to a pack of cells and see if the
total ESR is any more than slightly over the typical ESR of each cell
multiplied by the number of cells. A higher than expected reading indicates
one or more bad cells or possibly high resistance spot welds inside the
pack.

It can take hours to do a charge and discharge tests on a packs of cells -
but only SECONDS to do an ESR test on a pack and find immediately that no
further testing is warranted.



..... Phil