At 08:10 PM 11/10/2010  -0800, Mark L. Hineline wrote:
>Is the shorter-but-still-measurable-in-years story right?

It all depends on how deeply you discharge it.  True deep-cycle
batteries are good for about a thousand cycles if you only discharge
to 50%; maybe 200 if you discharge to 80%.  Starting batteries aren't
*meant* to be deeply discharged ever.  They're optimized for
delivering huge current for brief intervals, but mostly operating in
what's called float service -- no significant drains, charging
voltage 13.9 or so.  If starting takes 200 amps for five seconds,
that's about one-third of an amp-hour.

Optima makes a fancy one that they rate for fifty deep discharges to
80% (i.e. 20% charge remaining) -- normal starting batteries wouldn't
survive that.

Yours,
David