I have thought about this many times.  For our "house" batteries we
don't really care about CCA, we are concerned about capacity.  I have
gently used various "inappropriate" batteries for my house battery
over the years, like starting batteries or SLA batteries designed for
UPS systems.  I have found it hard to even find out the capacity of
these batteries, they just advertise CCA.

I have wondered what would be a good laymans way to determine the
remaining capacity in these batteries as they age.  Maybe
this:  Charge them up. Let them rest for a while to get a good
resting voltage.  Put a known load of a couple Amps on them for a
fixed time.  (Not discharging too low of course.)  Let them rest
again.  Measure an ending voltage.  Calculate something.  There must
be some Electrical gurus (like David B.) on this list who could
devise a good method so that we don't have to buy that $3K analyzer.

Edward

At 10:17 PM 8/12/2011, Jim Arnott wrote:
>"The purpose of battery testing is to estimate the end of battery
>life. Automotive technicians are most familiar with CCA, a measurement
>that reflects engine cranking but does not always predict the end of
>battery life correctly. The leading health indicator of a battery is
>capacity. So we ask, "At what capacity should the battery be replaced?""
>
>http://www.ecnmag.com/Articles/2011/04/Design-Talk/Battery-Testing-at-Garages-Simplified/
>
>
>Go check out the article. See what $3k+ gets you....