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Re: (ET) Min. battery voltage

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.

Always check voltage while under load. That's when you can get a reasonable reading. If you're dropping below 10.5 volts under load, you are running the risk of reversing a cell.

Anyhow, I have one (12V) battery that seems to be not so good, it reaches
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
That is a battery that is reversing. Consider it "toast"

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?

When it dips to 10.5, though my guess is it will fall thru to 6 really fast after that.

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

10.6 volts.



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