Usable Battery Capacity Calculator

A 100Ah battery is not always 100Ah you can use. Here is the real figure.

How much of a battery you can use depends on its type and how long you want it to last. This shows the usable amp-hours and watt-hours. Everything is worked out in your browser. Nothing is saved or sent anywhere.

1. Your battery

Lithium often 80 to 90%. AGM about 50% for long life.

2. Results

How it was worked out

    What this does and doesn't tell you

    • Check the maker's data sheet for the recommended depth of discharge and cycle life.
    • Capacity drops in the cold and as the battery ages.
    • Work on 240V AC wiring, including inverter outputs and mains inlets, must be done by a licensed electrician. For high-current DC gear, follow the maker's installation manual and have an auto electrician check your work if you're unsure.
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