Battery System Current and Power Calculator

Use this calculator to determine the total current and power requirements for your auxiliary battery system.

Click/press on the dots to enable or disable an accessory and compare the system load when various accessories are turned on.

The default system voltage is set to 13.6V, which is the voltage of a fully charged LiFePO4 battery. Adjust the system voltage with the slider to see how increasing or decreasing the voltage affects the amount of current drawn from the battery.

To determine the current or power required for each accessory check the manual (or website) for the product's specifications. Look for a power rating or current draw. Typically this will be the maximum current or power used by the device. Devices like inverters may also provide a no load or standby rating for when the device is on but not otherwise being used.

For 110V devices, a rough estimate of current required for your inverter can be made by taking the amps at 110V and multiplying by 12. Inverters aren't 100% efficient so we recommend adding at least 10-20% as an extra margin.

Either amps or watts can be entered in the calculator, the other field will be filled in automatically. To convert from milliamps (mA) divide by 1000 (e.g. 250mA is 0.25A).