Battery Sizing Chart
1. Determine total watt-hours per day
2. Determine days of storage required. This approximates the greatest number of cloudy days in a row expected (3 to 7 is common for residences, 7 to 14 for remote communications and monitoring sites.
3. Multiply line 2 by line 1
4. Determine planned depth of discharge. 80% is the maximum for lead acid deep cycle batteries, 50% is common amount for optimum longevity. Divide line 3 by .80 or .50.
5. Derate your batter for low temperatures by multiplying the answer in line 4 by the factors in the table above using the lowest expected weekly average temperature.
6. Find the watt hour capacity of your selected battery. Voltage x Amp Hour capacity. Example 6 volts x 350 amp-hours = 1200 watt hours.
7. Divide line 5 by line 6. This will be how many batteries you will need.
Round the number of batteries to fit the voltage such as a 24 volt system will need sets of 2 when using 12 volt deep cycle batteries, or a set of 4 batteries when using 6 volt deep cycle batteries.
