| Load | Estimated Runtime |
|---|
How Battery Runtime Works
Runtime comes down to usable energy divided by load. A battery’s rated capacity in amp-hours, multiplied by its voltage, gives watt-hours of stored energy — but you can only safely use part of that. Divide the usable watt-hours by your load in watts and you get hours of runtime.
Depth of Discharge Changes Everything
A 100 Ah lead-acid battery is really a 50 Ah battery in practice, because draining it below half ruins it quickly. Lithium batteries flip that, safely giving up 80 to 100 percent of their rating. That single difference often doubles real-world runtime for the same labeled capacity.
Sizing a Battery for the Job
Working backward is just as useful: decide how many hours you need, multiply by your load, and divide by usable capacity to find the amp-hours required. The helper above does this so you can size a battery bank for a fridge, lights, or a night of camping.
Frequently Asked Questions
Why is my real runtime shorter?
Cold temperatures, an aging battery, high discharge rates, and inverter losses all cut into the ideal figure. Build in 20 to 30 percent margin for real trips.
What usable percentage should I use?
Use 50 percent for flooded or AGM lead-acid and 80 to 100 percent for LiFePO4 lithium, depending on how hard you want to push it.
Does running through an inverter change things?
Yes. An inverter is 80 to 90 percent efficient, so AC loads pull more from the battery than their watt rating suggests. Lower the efficiency value to account for it.