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
new newsgroup users info : http://vancouver-webpages.com/nnq
GPS and NMEA info: http://vancouver-webpages.com/peter
Vancouver Power Squadron: http://vancouver.powersquadron.ca