WIN-J · EVERYDAY & WORK TOOLS
Camping battery runtime calculator
Estimate power-station runtime from capacity, appliance wattage and duty cycle. Include charge level, reserved energy, conversion efficiency and idle draw, then find the capacity needed for your target duration.
Results
Estimate assumes your efficiency and a constant average load. Temperature, ageing, automatic cut-off, starting surges and simultaneous charging are excluded. Set efficiency for your product and output type.
How to use
- Enter rated battery capacity and its unit. Ah and mAh also require nominal voltage.
- Set starting charge, reserved charge, conversion efficiency and battery-side idle draw.
- Enter each appliance's running power, quantity and duty cycle, then set the target duration.
- Review the results and output-limit message, then save a CSV containing the calculation settings.
Example
With 1,000 Wh, 100% starting charge, 10% reserve, 90% efficiency and 5 W idle draw, a 50 W fridge running half the time plus two continuous 10 W lights average 45 W. Battery draw is 55 W and usable energy is 900 Wh: about 16 h 21 min. An 8-hour target needs approximately 488.89 Wh of rated capacity.
Method and limitations
Wh = Ah × nominal V = mAh × nominal V ÷ 1,000. Usable battery Wh = rated Wh × (starting charge−reserve) ÷ 100. Average appliance W = Σ(running W × quantity × duty cycle ÷ 100). Battery draw W = average appliance W ÷ (efficiency ÷ 100) + battery-side idle W. Runtime = usable battery Wh ÷ battery draw W. Required rated Wh = battery draw W × target hours ÷ usable fraction. Idle draw is added once on the battery side. A zero usable fraction gives zero runtime and no finite required capacity. Supports up to 30 appliance rows, 100 units per row and 8,760 target hours. A single average efficiency is used; results do not guarantee exact product runtime or connection compatibility.
Frequently asked questions
Can mAh alone determine runtime?
Nominal voltage is also required. For example, 20,000 mAh × 3.7 V ÷ 1,000 = 74 Wh. Check which voltage the manufacturer's capacity rating uses.
Is 90% efficiency appropriate for every device?
The default is an example. Efficiency varies by product, output and load. Use manufacturer data or measurements, checking that idle draw and conversion losses are not counted twice.
How should I enter fridge power?
Use running power with its actual duty cycle, or measured average power with a 100% duty cycle. Applying both reductions can underestimate consumption.