Amp-hours measure charge; watt-hours measure energy. This guide shows how to calculate Wh from Ah and voltage—bank capacity, nominal bus V, and stored energy for apples-to-apples comparisons.
Benefits
- Single-step: Wh = Ah × V (multiply, no unit tricks).
- Works for single blocks and summed series/parallel banks.
- Outputs kWh by dividing Wh by 1,000 for utility-scale reads.
How it works
- Confirm total bank Ah (parallel adds Ah; series keeps Ah).
- Use nominal system voltage (series adds V; parallel keeps V).
- Multiply Ah × V for Wh—compare packs at different voltages fairly.
FAQ
How do I calculate Wh from Ah and voltage?
Wh = Ah × V. Example: 280 Ah at 48 V → 280 × 48 = 13,440 Wh (13.44 kWh). For 200 Ah at 12 V: 200 × 12 = 2,400 Wh. Voltage must match the Ah rating bus—do not mix cell V with pack Ah from a different string.
How do series and parallel strings affect Wh?
Series raises voltage; parallel raises Ah. A 4S2P 100 Ah 3.2 V LiFePO4 block: 12.8 V × 200 Ah = 2,560 Wh. Calculate Wh after resolving total bank Ah and system V—not per-cell mAh alone unless you rebuild the string math.
Should I use nominal or fully charged voltage?
Use nominal bus voltage for planning—12 V lead-acid, 48 V LiFePO4 nominal, 3.7 V Li-ion cell. Float and charge voltages are higher temporarily; energy comparisons across products use nominal V unless the datasheet specifies otherwise.
Technical specifications
- Wh = capacity_Ah × nominal_V.
- kWh = Wh ÷ 1,000.
- Series: V adds; parallel: Ah adds (for Wh, use totals).
- Related: battery-energy-calculator-wh, ah-to-wh, battery-bank-size.