Battery Runtime Calculator

This tool does two things:

• Runtime estimator – tells you how long a battery will power your device.
• Battery‑size helper – works backward from load and desired hours to suggest the minimum capacity you should buy.

How to use

• Select Battery Voltage
  Pick 12 V, 24 V, 36 V, 48 V or choose Custom and enter any voltage. To ensure your system uses the correct conductor size for your battery setup, you can also check this solar wire sizing  to avoid efficiency loss and overheating.
• (Optional) Click “What size battery do I need?”
  1. Enter the Application Load and choose its unit (W, kW, A, mA, Ah, or mAh).
  2. Enter the Desired Runtime in hours or minutes.
  3. Choose the Battery Type to apply the right depth‑of‑discharge limit.
  4. Tick condition boxes if the battery will run in cold weather or is already older than six months.
  5. Press Calculate Battery Size. The calculator fills the “Enter Battery Capacity” box for you.
• Enter Battery Capacity
  If you already know the capacity, type it and pick the unit (Ah, mAh, Wh, or kWh).
• Enter Device Load
  Type the load value and choose the matching unit (W, kW, A, mA, Ah, or mAh).
• Need more precision?
  Tick Show advanced options and adjust any field you know:
  • Ambient Temperature (°C, °F, or K).
  • Initial State of Charge (%).
  • Maximum Depth of Discharge (%).
  • Inverter Efficiency (%).
  • Battery Efficiency (%).
  • Peukert Exponent (for high current drains).

  You can leave any advanced box empty; the calculator uses safe defaults.

• Click “Calculate Runtime”
  The result appears below in hours and minutes.
• Reset clears every field and hides the helper and advanced panels.

Key benefits

• Instant estimate for phones, laptops, RV, UPS, and solar batteries.
• Battery‑size helper removes the guesswork when shopping for a new pack.
• Supports capacities in Ah, mAh, Wh, or kWh and converts automatically.
• Converts loads between Watts, Kilowatts, Amps, milli‑amps, and Amp‑hours.
• Advanced section models temperature, aging, discharge limits, inverter losses, and Peukert effects for professional‑grade accuracy.

• If you are planning a solar-powered setup, combining this tool with our solar investment return estimator can help you understand both runtime performance and long-term financial savings.