Battery Runtime Calculator
How long will your battery run a given load? Chemistry-aware DoD, optional inverter efficiency, and starting state of charge for LiFePO4, AGM, Gel, and lead-acid banks at 12V, 24V, or 48V.
Battery Runtime Calculator
DoD 80% · round-trip eff 95%
Advanced settings
Runtime
Discharge rate: 0.05C (60W effective load on 100Ah)
Need a complete wiring diagram?
VoltPlan designs full electrical systems with automatic wire sizing, fuse placement, battery configurations, and solar.
Design Your SystemCommon Camper & Boat Loads
Approximate continuous wattage for the loads people most often plug into the runtime calculator. Add up the loads that run at the same time for your real-world worst case.
| Load | Typical Watts | Type |
|---|---|---|
| LED light strip (full) | 10–25 W | DC |
| 12V compressor fridge (avg) | 40–60 W | DC |
| Roof vent fan | 3–10 W | DC |
| Diesel heater (combustion only) | 20–40 W | DC |
| Water pump (running) | 50–80 W | DC |
| Laptop charger (typical) | 45–90 W | AC via inverter |
| Coffee maker (drip) | 900–1500 W | AC via inverter |
| Microwave (1.0 cu ft) | 1100–1500 W | AC via inverter |
| Induction cooktop (single) | 1500–1800 W | AC via inverter |
| Hair dryer | 1200–1800 W | AC via inverter |
| Air conditioner (small RV) | 800–1500 W | AC via inverter |
Frequently Asked Questions
How long will a 100Ah battery last?
Depends on the load. 100Ah 12V LiFePO4 = 1280Wh, 80% DoD = 1024Wh usable. 50W load → ~20h. 500W load → ~2h. Use the calculator above for your specific case.
What is depth of discharge (DoD)?
How deep you can drain before damaging the battery. LiFePO4: 80%. AGM/Gel/Lead-acid: 50%. The calculator caps usable energy at the DoD limit, not nameplate Ah.
Does inverter efficiency matter?
Yes. AC loads through an inverter pull extra power for conversion (~5–10%). Set the slider in advanced settings to match your inverter.
Why is a lead-acid battery worse than the spec suggests?
50% DoD limit + Peukert effect (capacity drops at high discharge rates). LiFePO4 is mostly Peukert-immune.
Can I drain to 0% in an emergency?
Once or twice, probably. Repeatedly: no. Cycle life drops sharply below the DoD limit. The "full discharge" number in the result is theoretical, not safe.
How does temperature affect runtime?
Cold reduces usable capacity. Below 0°C, expect 70–85% of rated Ah. LiFePO4 also will not charge below 0°C without a heater.
Related Calculators
Battery Bank Sizer
Reverse direction — given runtime targets, get the required Ah.
Battery Charge Time Calculator
After you discharge — how long to charge back up from a charger or solar.
Ah ↔ Wh Converter
Convert between battery Ah and stored Wh / kWh.
Inverter Size Calculator
Pick an inverter sized for your AC load list.