Things we should know: P = V . I (ie. power in watts = volts x amps) Every battery has a amps/hr (Ah) rating which signifies for how many hours it can deliver that much amount of current? for eg. 2000mAh battery can deliver 2000mili Amps per hour Eg.1 Inverter battery standby calculation 1.Calculating the total battery capacity in Watts/hr: if our inverter battery has a rating of 150Ah and voltage 12V thus it can deliver 150Amps per hour. thus power delivered per hour will be 1800Watts/hr (1800 = 12 x 150) .............................( P = V . I ) 2.battery threshold level : (actual battery capacity) now before proceeding take into consideration that the battery wont be fully discharged due to the internal protection circuit in the inverter so we have to first take 85% of our total battery ca...