How Long Will a 50Ah Battery Last?

Answer
4.9 h at 100 W (LiFePO4)

A 12 V 50 Ah battery stores 600 Wh. Using 90% of a LiFePO4 battery through a 90% efficient inverter leaves 486 Wh, enough for 4.9 hours at 100 W. Lead-acid gives about half that because only 50% should be used.

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How we calculated this

    For estimating and educational purposes only. Results are approximate and are not a substitute for a licensed professional, the manufacturer's instructions or your local code. Disclaimer

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    Runtime by load (12 V, through a 90% inverter)

    LoadLiFePO4 (90% usable)Lead-acid (50% usable)
    25 W19.4 h10.8 h
    50 W9.7 h5.4 h
    100 W4.9 h2.7 h
    200 W2.4 h1.4 h
    300 W1.6 h0.9 h
    500 W1.0 h0.5 h
    1000 W0.5 h0.3 h

    Lead-acid runtimes at high loads are optimistic because of the Peukert effect.

    Frequently asked questions

    Can a 50Ah battery run a refrigerator?

    A 12 V fridge averaging 50 W would run about 11 hours on lithium (no inverter needed for a 12 V fridge).

    How many watt-hours is 50Ah?

    600 Wh at 12 V, or 640 Wh for a 12.8 V LiFePO4 battery.

    Open the full calculator: Battery Runtime Calculator →