askvity

How to Calculate Battery Watt-Hours?

Published in Battery Calculations 2 mins read

To calculate battery watt-hours (Wh), you multiply the battery's voltage by its amp-hour (Ah) capacity. Watt-hours represent the total energy a battery can store.

Understanding Watt-Hours

Watt-hours (Wh) are a measure of energy, while amp-hours (Ah) are a measure of charge capacity. Knowing watt-hours is crucial for understanding how long a battery can power a device.

Formula for Watt-Hours

The formula for calculating watt-hours is:

  • Watt-hours (Wh) = Voltage (V) x Amp-hours (Ah)

Calculating Watt-Hours: Step-by-Step

Here's how you can calculate watt-hours using the formula:

  1. Identify the Battery Voltage (V): Check the battery’s label or specifications for its voltage. Common voltages are 12V, 24V, 36V, or 48V.
  2. Identify the Battery Amp-hour Capacity (Ah): Find the Ah rating on the battery label. This tells you how much charge the battery can store.
  3. Multiply Voltage and Amp-hours: Use the formula: Wh = V x Ah to get the watt-hour capacity.

Examples

Let's illustrate with a couple of examples using information from the reference provided:

  • Example 1: A 12-volt battery with a capacity of 100Ah

    • Wh = 12V * 100Ah
    • Wh = 1200Wh

  • Example 2: A 24-volt battery with a capacity of 50Ah

    • Wh = 24V * 50Ah
    • Wh = 1200Wh

Notice that both batteries in the examples have the same total energy capacity of 1200 Wh, even though their voltages and amp-hours are different.

Practical Implications

Understanding watt-hours is beneficial for:

  • Comparing Battery Capacity: You can compare different batteries by their watt-hour capacity, regardless of their voltage.
  • Estimating Device Runtime: You can roughly estimate how long a battery can power a device by dividing its watt-hour capacity by the power consumption of the device (in watts).
  • Choosing the Right Battery: When selecting a battery, consider both voltage and amp-hour capacity to find a battery that matches your energy requirements.
Battery Type Voltage (V) Amp-hours (Ah) Watt-hours (Wh)
Battery 1 12V 100Ah 1200Wh
Battery 2 24V 50Ah 1200Wh

Related Articles