Tell Battery Buddy your appliances and how many hours of backup you need. Get the inverter VA, battery Ah, system voltage, series configuration, charger current and a start-up surge overload check — with every formula shown.
Required VA = (average load in watts / power factor 0.8) x 1.25 safety margin, rounded up to the nearest standard Indian retail tier. It also runs a start-up surge check against that tier.
Energy needed = load x desired backup hours. Required Ah = energy / (system voltage x efficiency x 50% depth of discharge). The result is matched to the nearest standard bank in the master sizing table.
Because average load crossed 400W or 800W. Higher system voltage moves the same power at lower current, which reduces cable losses, heat and the wiring cost of a safe install.
Roughly C/10 to C/8 of the bank capacity — 15-19A for a 150Ah bank. Under-charging leaves a lead-acid battery permanently short of full; over-charging cooks the electrolyte.
Battery Buddy is free, needs no sign-up, sells no batteries and shows every formula it uses. It is built by Flocci Technologies, an India-first AI-native software studio behind 30+ apps that share one Flocci identity.