Battery Energy Capacity
Energy stored from voltage and charge capacity.
Formula
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Example
48 V × 100 Ah = 4800 Wh = 4.8 kWh
How it works
This formula estimates how much energy a battery can store by combining its voltage with the amount of charge it can deliver. Voltage tells you how much energy each unit of charge carries, while ampere-hours measure how much charge the battery can supply over time; multiplying them gives energy. In electrical terms, watt-hours are the product of volts and ampere-hours, which is why this works for battery capacity calculations.
When to use it
Use this when comparing batteries, sizing a backup power system, or estimating how long a battery bank can run a load. It is common in solar, off-grid power, electric vehicles, and portable electronics.
Worked example, step by step
Step 1: Identify the values V = 12 V Q = 150 Ah Step 2: Use the formula E = V × Q E = 12 × 150 Step 3: Calculate the energy E = 1800 Wh Step 4: Convert to kilowatt-hours if needed 1800 Wh ÷ 1000 = 1.8 kWh Final answer: The battery stores 1800 Wh, or 1.8 kWh, of energy.
Common mistakes to avoid
- Using milliamps-hours (mAh) as if they were ampere-hours (Ah) without converting
- Treating Wh and Ah as the same unit instead of multiplying by voltage
- Ignoring that real batteries deliver less usable energy than their rated capacity
Did You Know?
A typical home battery stores 5–14 kWh — enough to run a house through an evening peak.
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