That's why I said you really should have an AH meter.
The 12.2V is a resting voltage which is the only way to
determine level of discharge by measuring voltage. Also,
the 12.2V is for liquid electrolyte batteries (obsolete
technology IMHO) but cheap in the short term.

Doug
s/v Callista

"Jeff Morris" wrote in message
...
12.2 is rather high if the load is large. Also, different batteries have
different characteristics.

I use an Amp-Hour meter, but also watch the voltage. If my fridge is
running -
a 30 Amp load - the Voltage can go to 11.9 even if the batteries are down
only
25%. Anything lower than 11.8 is getting pretty low on most batteries.

The fully charged, no load Voltage is only of minor interest, since it
isn't a
very reliable measure of anything. Once even a load is put on, it drop
down to
about 12.6. If all you have is a Volt meter, its a bit difficult
determining
what's really going on - too much depends the load and the recent history.


"Doug Dotson" wrote in message
...
Or to state it another way if you don't have an amp-hour
meter (which you should), 12.2 volts is a good lowest
voltage.

DOug
s/v Callista

"Peter Bennett" wrote in message
news.com...
On Sat, 20 Dec 2003 19:39:04 +0100, "Ric" wrote:

I have just bought a couple of Delphi Freedom marine deep cycle
batteries
for my service bank. Is there a recommended minimum voltage below
which
one
should not discharge? Also, if the nominal capacity is (say) 100Ah,
is
that
measured between standard voltages or is it measured from a nominal
full
charge (with full charge voltage dependent on the charging system)
until
totally discharged - ie 0v? Or is there a standard "never go below"
voltage
which manufacturers use?

10.5 volts is considered "fully discharged".

For best results, it is generally recommended that you should only
discharge a battery to 50%, so you should only take 50 AH from a 100
AH battery.




--
Peter Bennett, VE7CEI
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