(ET) Min. battery voltage

["Markus Lorch" <mlorch vt edu>]

To the battery gurus on this list:

I have read several posts and online documentation on the lowest
save voltage to which a lead acid deep cycle battery may be discharged
and found values around 10.5V / 80% (for a 12V bat).
I think this is consistent with what Chris' recent battery monitor
looks out for. 

The question I have is: Is this the lowest voltage under load or the
voltage immediately after load is removed? I read somewhere that to 
measure battery voltage one should let the battery sit for 2 days without
charging/discharging to get an accurate reading.

Anyhow, I have one (12V) battery that seems to be not so good, it reaches
low
voltages before the others do and when I keep mowing after I see it go to
10V it is getting very hot and drops to as low as 6V when you start the
mower
or start driving. If I stop the current flow it returns to about 11V or so
almost immediately. So when do I reach 80% depth of discharge, when the
battery first dips to 10.5V or when it holds 10.5V after load is removed?

Also at what voltage do I have to fear cell reversal? the other two 12V
sections
in my pack do not dip below 12V when this troublemaker is already below 
10V,
so I
am concerned about them forcing current through these weak/discharged 
cells.


Thanks
Markus