Battery Runtime Calculator for 12V, 24V and 60V Systems
Use this free battery runtime calculator to estimate how long a battery can power your 12V, 24V or 60V load. Enter your battery bank capacity, choose battery type and then enter the load as battery-side current or power.
Enter your battery and load details
Results
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How to use the battery runtime calculator
Enter your battery voltage and total battery bank capacity in amp-hours, then select the battery type. Next choose whether you want to enter the load as battery-side current in amps or as appliance power in watts. The calculator estimates usable battery energy and then calculates approximate runtime based on the selected load and reserve.
- Enter Ah for your total battery bank capacity.
- Choose Current (A) if you already know battery-side current draw.
- Choose Power (W) if you know the appliance wattage only.
- Use inverter = yes only when entering load power in watts and the load is powered through an inverter.
Why battery type matters
Different battery types have different practical depth-of-discharge limits. AGM and lead-acid batteries are usually not discharged as deeply as LiFePO4 batteries if you want good battery life. That means two batteries with the same Ah rating may give very different practical runtime.
Typical usable battery assumptions
| Battery type | Typical usable capacity | Comment |
|---|---|---|
| AGM / Lead Acid | 50% | Common practical assumption for battery life protection. |
| GEL | 60% | Often slightly deeper usable discharge than standard lead acid. |
| LiFePO4 | 90% | Usually allows much deeper usable discharge. |
How runtime is calculated
The calculator first estimates usable battery capacity based on battery type and selected reserve. In current mode it uses the battery-side current directly. In power mode it converts watts to battery-side current using system voltage, and includes inverter efficiency losses if inverter mode is selected.
Example runtime checks
Example 1: A 12V 100Ah AGM battery powering a 5A battery-side load may run for many hours, but not all 100Ah is treated as usable.
Example 2: A 12V 100Ah LiFePO4 battery usually provides much more practical runtime than a 100Ah AGM battery.
Example 3: A 230V appliance powered through an inverter uses more battery energy than the appliance wattage alone suggests because inverter losses must be included.
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FAQ
It depends on battery size, battery type, usable depth of discharge and the real load. This calculator gives a practical estimate rather than a perfect real-world guarantee.
Yes. In power mode the calculator converts watts to battery-side current using system voltage and inverter efficiency if selected.
Because a larger proportion of the rated capacity is typically usable in real applications without reducing battery life as quickly.
Yes. Leaving a reserve is a practical planning method because real-world loads vary and most users do not want to fully drain the battery in normal use.
Yes. If the load is powered through an inverter, the battery must supply more energy than the appliance actually consumes because some energy is lost in the inverter.
These calculator results are provided as a practical technical guide only. Final battery sizing, cable size, fuse protection, installation method and equipment selection should always be verified against the real application, installation environment and manufacturer specifications. Electrical systems should be installed using appropriate protection devices and suitable cable routing for the intended load conditions.