Can I calculate runtime if I only know the battery voltage and load power?

Usable battery capacity refers to the percentage of the nameplate capacity that can be safely discharged before recharging; entering a lower percentage will reduce the calculated runtime accordingly.

How does system efficiency affect the runtime result?

The calculator supports both series and parallel battery configurations by allowing multiple voltage and capacity inputs, though the interface primarily treats entries as a single equivalent source.

Miscellaneous CalculatorsTool Review

Battery Size Calculator

Provided byCalculator Academycalculator.academy

This battery run time tool calculates runtime, required capacity, or power relationships using battery capacity, volt...

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About this tool

What Battery Size Calculator does

The Battery Run Time Calculator at Calculator Academy determines battery runtime, required capacity, or supported load by accepting battery voltage, capacity, and power or current draw. Users can solve for any missing variable, with inputs accepting standard units such as volts, amp-hours, milliamps, watts, and kilowatts. The tool also includes advanced options for specifying usable battery capacity as a percentage and system efficiency to account for inverter or conversion losses. Results display the calculated runtime in hours, minutes, or days, providing a practical estimate for single batteries or configured bank systems.

Step by step

How to use the Calculator Academy Battery Size Calculator

1
Select the variable you need to solve for: battery run time, required capacity, or supported load power
2
Enter the battery voltage in volts, millivolts, or accepted units
3
Input the battery capacity in amp-hours, milliamp-hours, or accepted units
4
Specify the load as power (watts, kilowatts) or current (amperes, milliamperes), and optionally set usable capacity percentage and system efficiency
5
Click Calculate to view the estimated runtime in hours, minutes, or days

Is it right for you

Best for

Ideal for hobbyists, RV owners, and off-grid system designers who need quick estimates of battery runtime or required capacity for DC loads, especially when accounting for usable capacity and conversion efficiency.

Limitations

Results are theoretical estimates and may vary with real-world conditions
No support for unit switching beyond the listed metric and milli-unit options
Does not model temperature effects or battery aging on actual performance

Questions

Battery Size Calculator FAQ

Can I calculate runtime if I only know the battery voltage and load power?: Usable battery capacity refers to the percentage of the nameplate capacity that can be safely discharged before recharging; entering a lower percentage will reduce the calculated runtime accordingly.
How does system efficiency affect the runtime result?: The calculator supports both series and parallel battery configurations by allowing multiple voltage and capacity inputs, though the interface primarily treats entries as a single equivalent source.

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