Find out how long your battery bank will power your home or cabin.
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Multiply your battery capacity (Ah) by system voltage (V), the number of batteries, and your usable depth-of-discharge, then divide by your load in watts. For example, a single 100Ah 12V LiFePO4 battery at 80% usable gives 960Wh, which runs a 300W load for about 3.2 hours.
Lithium LiFePO4 batteries safely deliver about 80% of their rated capacity, while AGM, gel, and flooded lead-acid batteries should only be drained to about 50% to avoid damage. That means a lithium battery gives you roughly 60% more usable runtime than a lead-acid battery of the same Ah rating.
Size your bank so its usable watt-hours cover your daily energy use multiplied by the number of backup days you want. For true off-grid resilience without solar input, aim for at least 2 to 3 days of storage so cloudy stretches do not leave you in the dark.
Runtime depends on total watt-hours, not voltage alone, so a 12V and a 48V bank with the same total Ah-per-voltage energy last the same time on the same load. Higher voltage systems like 24V or 48V mainly reduce wiring losses and let you run larger inverters more efficiently.
Bugs, confusing bits, or ideas — all welcome. Thank you!
