To size a battery bank we take the hours needed continuously x watts = total watts/DC volts=amps needed.
Example: 3 hours of run time needed * 1500 watts = 4500 watts total / 12 volts DC = 375 amps. You will need a total of 375 amps of stored power in the batteries. We don’t recommend fully depleting your batteries so keep this in mind when you are calculating the number of batteries needed.
Here is another example: Let’s say you purchase a 2000 watt inverter 12 Volt. If you max out the inverter at 2000 watts, you are pulling 2000 watts /12 volts = 166.6 DC amps per hour. If you use a 200 amp 12 volt battery you would divide 200 amp battery / 166.6 amps = 1.2 hours of run time. This is if you plan on fully depleting the battery, which we DON’T recommend. We recommend 50% depth of discharge. Since we recommend 50% depth of discharge, you would divide 1.2 hours /50% = .60 hours. If you use 30% depth of discharge you divide 1.2 hours/30%=.36 hours.