On Wed, 16 Jun 2004 11:09:23 -0400, Guy Fawkes wrote:

Nigel wrote:

Stupid question time...
If I have a 100ah battery how much power can I expect to get out of it...
is 100ah the total battery capacity or it's useable/available capacity. My
understanding is that a normal lead acid battery shouldn't be run too
flat, so when is flat too flat? If I should only let my battery drain down
to say a 90% charge, have I only got 10ah before I need to recharge?

batteries are USUALLY rated on a 10 hour cycle, so a brand new and fully
charged 100Ah battery with put out 10 A for 10 hours, a 60 Ah battery will
put out 6 A for 10 hours, and so on.

snip

Also worth mentioning that discharge at a higher current (ie over
shorter time) will produce less amphours - doubling current drain
might take 10percent off amphours. For this reason, batteries are
often quoted at 20 hour rate (C20).

Ian