Run one discharge test with a single known load and find your inverter and battery's true efficiency factor. Apply it to the backup calculator in one click and stop guessing at 85%.
Fully charge the battery, disconnect everything except one appliance of known wattage, run it until the inverter cuts off, and note the hours. Efficiency = (Load watts x Hours run) / (Battery Ah x 12V).
0.65-0.80 for a healthy new tubular battery and inverter. 0.45-0.60 suggests real degradation; below 0.40 the battery is usually near end of life.
Because the test measures the whole chain, not the inverter alone. Battery age and sulphation, low electrolyte, thin cabling and corroded terminals are all folded into one number — and the battery usually dominates.
Yes, in one click. The measured factor is passed to the backup calculator through the URL, so every subsequent estimate uses your system rather than an assumption.
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.