RE: [A/S] battery power

["Craig Eldridge" <craig_e@xxxxxxxxxxx>]

If you have a group 27 battery then you will have either a 105 amp hr. or 
115 amp hr. battery.  Since you do not want to run the battery down much 
over 50%, let's say you have 55 amp hours to work with.  Check to see what 
amperage draw per hour you have and that will let you know how much time you 
have for nearly continuous running (which we know does not happen since the 
furnace cycles on and off).

I have one 115 amp hr. Duralast deep cycle and I have run a 34,000 BTU 
furnace for 7 hours with no ill effects while not hooked to shore power.  It 
is drawing 7.5 amps.  A 35 watt solar panel helped during the day with some 
of the power loss occuring at night.

The 24,000 BTU draws 3.5 amps, the 30,000 draws 5.5 amps and the 40,000 
draws a whopping 9.5 amps.

My '77 31' Excella had 2 Delco Voyager 105 amp hr. batteries for 210 amp 
hrs.  The 30,000 BTU furnace did fine for the 3 days I was boondocking with 
the solar panels.  This was with the furnace running two hours at mid 
afternoon in 40 degree weather and a little less than 7 hours at night.