On 27 Feb, 11:42, "Dave Liquorice"
wrote:
On Fri, 27 Feb 2009 10:58:53 +0000, T i m wrote:
I was looking about to see if anyone had an affordable solution for
testing realistic battery capacity out there.

For wet cells the specific gravity of the electrolyte tells you the state
of charge.

State of charge isn't the same as capacity, as the total capacity of
the cell falls with age - s.g. only tells you what proportion of this
total you can still expect, not how big a pot might be available.

The claims for this gadget are clear enough, but it's hard to tell how
accurately this "frequency response" technique maps onto actual
capacity. You'd have to do 100s of long-term discharge cycles to know
for sure, as they do indeed claim to have done.