[Ozarkguy]

Determining your battery bank requirements
1. Converting AC amps to Watts: AC amps x 120 Volts = Watts
2. Convert Watts to Actual DC amps: (Watts / 12) x 1.1 = actual DC amps
3. amp hours consumed between charge cycles:
run-time of appliance (hours) X actual DC amps = amp hours consumed
4. Number of batteries required:
(Total amp hours consumed X 2*) / amp hour rating of battery = Number of batteries required
*Since deep cycle batteries should only be discharged to 50% total capacity, the total amp hours consumed between charge cycles should be multiplied by 2.
Example:
amp hours consumed between charge cycle = 126
amp hour rating of battery = 90 (Group 27)
(126X2) / 90 = 2.8
(Round up to the nearest whole number.)
Therefore, the minimum number of batteries required is three with the above values.

Typical Battery Amp Hour Rating
Battery Size Amp Hour Rating
Group 27 90
Group 31 105
4D 160
8D 220
6V Golf Cart 225