100AH inverter battery: how much backup does it really give?

"100AH" tells you how much charge the battery stores, not how long your fans will run. Converting one into the other takes two constants that no box ever prints: inverter efficiency, and the share of the charge you can safely use.

The calculation

A 100AH 12V battery holds 1200 watt-hours on paper. After inverter losses (roughly 20%) and keeping discharge to 60% so the plates survive, you have about 576Wh to spend.

What that means at real loads

• 200W (lights and two fans): about 2 hours 53 minutes
• 400W (lights, fans, TV): about 1 hours 26 minutes
• 600W (add a fridge): about 0 hours 58 minutes
• 800W (small shop): about 0 hours 43 minutes

Anyone quoting you double these figures is quoting a 100% discharge — which a lead-acid battery will tolerate perhaps a hundred times before its capacity collapses.

Charging time

Expect roughly 9 to 13 hours from flat to full, depending on the charging current your inverter supplies. If your area gets less mains time than that between cuts, a larger battery will never reach full charge and will sulphate — a smaller battery is genuinely the better buy.

Who should buy 100AH

This is the right size for a single room, a PG, a small shop or a rented flat where the load is a few lights and fans and the battery may have to be moved.

Before you order

1. Check your inverter's charging current supports this capacity — an undersized charger will never fill it.
2. Measure the trolley space, including height with the vent caps open.
3. Keep the old battery for exchange; its scrap value comes off the bill.
4. Confirm the warranty split between full replacement and pro-rata months.

Backup figures above are calculated at 80% inverter efficiency and 60% usable depth of discharge — the numbers a battery gives in a real home, not on a test bench. Actual results vary with battery age, ambient temperature and how many appliances are switched on together.

Order in Telangana or Andhra Pradesh

Battery Express delivers across Telangana and Andhra Pradesh, with the old battery collected at the door and its scrap value adjusted against your bill. Browse the full range on our products page, or message us with your model number and we will confirm the exact fitment before you pay.

Delivery is currently limited to Telangana and Andhra Pradesh. If your PIN code falls outside these two states, checkout will let you know rather than take an order we cannot deliver.