Lithium Battery Run Time Calculator
Professional battery life estimator for solar, backup, and RV systems. Account for discharge depth, system losses, and device loads instantly.
Estimated Battery Life
| Connected Device | Qty | Consumption (W) | Total Load |
|---|
Add System Loads
Use the library or manual add to calculate duration.
Analyzing Lithium Runtime
Our lithium battery run time calculator uses precise energy equations to help you plan your power requirements. Lithium chemistry (specifically LiFePO4) offers a flat discharge curve, meaning you get consistent voltage until the battery is nearly empty.
However, system losses from inverters (typically 5-15%) and self-discharge must be considered. This battery life estimator allows you to model these variables for highly accurate real-world results.
Pro Configuration
- Inverter Efficiency Adjustment
- AH to WH Conversion
- Multi-Battery Bank Modeling
How to Calculate Battery Life
Define Capacity
Enter the total Amp-Hours (Ah) of your battery and the voltage (12V, 24V, etc.).
Adjust Efficiency
Set Inverter Efficiency (90% avg) to account for DC/AC heat loss.
Add Loads
Use the library to add devices like Fridges (60W) or Laptops (65W) to the profile.
Review Time
The yield converter instantly shows the estimated runtime in hours and minutes.
Most Searched FAQs
Q. How to calculate lithium battery run time?
To calculate the runtime of a lithium battery, you use the energy formula: (Total Ah × Voltage × DoD % × Efficiency %) ÷ Total Load in Watts. First, calculate the usable Watt-hours (Wh). For a 100Ah 12V lithium battery at 90% DoD and 90% inverter efficiency, you have roughly 972Wh of usable energy. Divide this by your device's wattage to get the runtime in hours.
Q. How long will a 100Ah battery run an appliance that requires 200W?
Assuming a standard 12V lithium system with 90% usable capacity (DoD) and a 90% efficient inverter, a 100Ah battery provides approximately 972 usable Watt-hours. If you run a constant 200W appliance, the calculation is 972Wh ÷ 200W = 4.86 hours. This means your appliance will run for approximately 4 hours and 51 minutes.
Q. How long will a 100Ah lithium battery run an appliance that requires 400W?
With a 400W load on the same 12V 100Ah setup (972 usable Wh), the calculation is 972Wh ÷ 400W = 2.43 hours. This results in an estimated runtime of 2 hours and 26 minutes. Higher loads increase internal resistance and heat, so actual real-world results may be slightly lower depending on your battery's BMS and wiring quality.
Q. How long will a 300Ah lithium battery last?
A 300Ah 12V lithium bank has a massive 2,916 usable Watt-hours (at 90% DoD/Eff). The duration depends entirely on your load:
- Running a 100W light/TV: ~29 hours
- Running a 500W large appliance: ~5.8 hours
- Running a 1500W microwave: ~1.9 hours