There is no safety issue. So probably you are concerned about
maximum battery lifespan. Right?
If so, 'st's comment is useless. His post would get you 100%
discharged (depth of discharge or DoD), and a car battery has very
few cycles to 100% DoD. You need to stop LONG before 100% to get
maximum life from your battery. I'd recommend 50% and that only if
desperate for power.
Battery will last the longest if you never discharge it. Keep it
floating at full-charge all the time. But that is a battery that
won't do much for you. Battery will last the least number of cycles
if you discharge it all the way every cycle. The less deep you go
each cycle, the more cycles you will get.
So you need to decide the compromise: less available energy by
shallower discharges but more cycles, or fewer cycles each with more
available energy.
The manufacturer of the battery can (or should be able to) give you
a chart showing number of charge/discharge cycles compared to DoD of
each cycle. Then from that you can calculate energy stored over the
life of the battery and determine your most cost effective DoD.
http://www.tpub.com/doeleadacid/leadacid14.htm
In order to obtain maximum life from lead-acid batteries, they should be
disconnected from the load once they have discharged their full capacity.
The cutoff voltage of a lead-acid cell is usually around 1.75 V. However,
please next time use google and "lead acid battery cutoff voltage"
Better to search for "state of charge" information:
http://www.google.com/search?hl=en&q=battery voltage "state of charge"
The homepower link is probably sufficiently detailed for most.
sdb
--
| Sylvan Butler | Not speaking for Hewlett-Packard | sbutler-boi.hp.com |
| Watch out for my e-mail address. Thank UCE. >>>> change ^ to @ <<<< |
It may be better to live under robber barons than under omnipotent moral
busybodies. The robber baron's cruelty may sometimes sleep, his
cupidity may at some point be satiated; but those who torment us for our
own good will torment us without end, for they do so with the approval
of their consciences. -- C. S. Lewis