For a 12 Volt System:
(10 x (Battery Capacity in Amp Hours) / (Load Power in Watts)) / 2 = Run Time in Hours
For a 24 Volt System:
(20 x (Battery Capacity in Amp Hours) / (Load Power in Watts)) / 2 = Run Time in Hours
Tip: Deep cycle (marine) batteries generally have the highest reserve ratings. They are also capable of withstanding repeated drains of power and recharging.
Tip: Engine start batteries should not be discharged below 90% charged state, and marine deep cycle batteries should not be discharged below 50% charged state. Doing so will shorten the life of the battery based on most battery manufacturers recommendations.
Note: If you intend to use power tools for commercial use, or any load of 200W for more than 1 hour regularly (between battery recharging) we recommend installing an auxiliary battery to provide power to the inverter. This battery should be a deep cycle type and sized to meet your run time expectations with the engine off. The auxiliary battery should be connected to the alternator through an isolator module to prevent the inverter from discharging the engine start battery when the engine is off.