Battery Capacity Calculator
Ah to Wh / Wh to Ah Conversion
Wh = Ah × V and Ah = Wh / V
Battery Runtime
Calculate how long a battery will last under a given load
Battery Charge Time
Estimate time to charge a battery
Formula
Wh = Ah × V | Runtime = (Ah × V × DoD) / (Load W / Efficiency) | Charge Time = Ah needed / (Charge A × Efficiency)
Frequently Asked Questions
What is the difference between Ah and Wh?
Ah (amp-hours) measures charge capacity regardless of voltage. Wh (watt-hours) measures energy and includes voltage: Wh = Ah × V. Two batteries can have the same Ah but different Wh if their voltages differ. Wh is better for comparing energy storage across different voltage systems.
What is depth of discharge (DoD)?
Depth of discharge is how much of the battery's total capacity is used. Lead-acid batteries should only be discharged to 50% to preserve lifespan. Lithium-ion batteries can typically handle 80% DoD, while LiFePO4 can handle 90-100%. Deeper discharge reduces battery cycle life.
What is C-rate?
C-rate indicates the charge or discharge rate relative to battery capacity. 1C means the battery is charged/discharged in 1 hour (e.g., 10A for a 10Ah battery). 0.5C takes 2 hours, 2C takes 30 minutes. Most batteries perform best at 0.2C-0.5C charging rate.
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