Formula & Calculator
Battery Energy (Watt-Hours)
Converts a battery's amp-hour capacity into watt-hours of stored energy using its nominal voltage.
Interpretation
Battery energy in watt‑hours: Wh = V × Ah converts the amp‑hour capacity into energy using the nominal voltage.
Example: A 12V battery with 100Ah stores 12 × 100 = 1200Wh (1.2kWh).
Variables
| Symbol | Quantity | Unit |
|---|---|---|
| Wh | Battery energy (watt-hours) | Wh |
| V | Battery nominal voltage | V |
| Ah | Battery capacity (ampere-hours) | Ah |
What it means
The energy stored in a battery in watt‑hours (Wh) is the product of its voltage and ampere‑hour capacity: Wh = V × Ah. This is a direct measure of total energy. For example, a 12V, 100Ah battery stores 12 × 100 = 1200 Wh = 1.2 kWh. This energy can be used to power devices for a certain time, considering inverter efficiency and depth of discharge. This calculation is essential for sizing battery banks in solar systems and for estimating runtime. Example: A 24V, 200Ah battery stores 24 × 200 = 4800 Wh = 4.8 kWh.
Worked example
Battery Energy (Wh) – Practical Example
Real‑World| Parameter | Value |
|---|---|
| V | 12 V |
| Ah | 100 Ah |
| Formula | Wh = V × Ah |
Common mistakes
Watch for unit mismatches (W vs kW, single- vs three-phase) and remember to include power factor or efficiency where the formula requires it.Applications
Battery energy in watt‑hours Wh = V × Ah converts amp‑hour capacity to energy using the nominal voltage. This gives the total energy stored. Engineers use it to compare battery systems, to calculate energy density, and to design power systems. This is a standard metric for battery energy.
- Battery energy storage system design
- Energy capacity comparison across technologies
- Calculation of runtime and power output
- EV and portable device energy assessment
- Educational understanding of battery energy
Frequently Asked Questions
The energy is Wh = V × Ah, where V is the nominal battery voltage and Ah is the amp‑hour capacity.
Divide by 1000: kWh = Wh / 1000.
Wh = 12 × 100 = 1200 Wh = 1.2 kWh.
Common errors: 1) using the wrong voltage, 2) not considering the actual usable capacity, 3) using peak voltage instead of nominal, 4) ignoring battery degradation.
Usable energy is limited by the depth of discharge (e.g., 50% DoD gives 0.5 × total Wh).
Comparing battery capacities, sizing energy storage systems.
Run time (hours) = (Wh × DoD) / Load power (W).
Low temperatures reduce the effective Wh capacity; derating factors apply.