Battery Sizing Calculator
Calculate the battery capacity (in amp-hours) needed to power a load for a given time at a specific voltage.
Battery Sizing Calculator
Calculate the battery capacity (in amp-hours) needed to power a load for a given time at a specific voltage.
Real-World Examples
60W fridge for 10 hours on 12V at 80% DoD
62.5 Ah
15W router for 24 hours on 12V at 50% DoD
60 Ah
40W LED lights for 6 hours on 24V at 80% DoD
12.5 Ah
Common Mistakes to Avoid
Ignoring depth of discharge (DoD) limits
Fix: Most battery types should not be fully discharged. Lithium batteries often allow 80-90% DoD, while lead-acid batteries are typically limited to 50% to preserve lifespan. Use the right DoD for your battery chemistry.
Using nominal voltage instead of actual discharge voltage
Fix: Battery voltage drops as it discharges. This calculator uses nominal voltage for simplicity. For precise sizing, use the average discharge voltage, which is slightly lower than nominal.
Forgetting inverter and system losses
Fix: If you are powering AC devices through an inverter, add 10-20% to account for inverter inefficiency. The calculator gives the ideal battery size; real systems need a margin for losses.