Battery Capacity

Calculator and formulas for calculating the battery capacity


This function calculates the capacity of a battery and the relationship between capacity, energy and voltage.

To perform the calculation, use the radio button to select which value should be calculated. Then enter the required values and click the 'Calculate' button.


Battery capacity calculator

 What should be calculated?
 Input
Capacity
Energie
Voltage
Decimal places
 Result
Capacity
Energy
Voltage

Battery capacity description


To calculate the capacity of a battery, we need some information, such as the voltage (volts) and the required discharge time or power consumption. Usually, the capacity is given in ampere hours (Ah) or milliampere hours (mAh). Here is the basic formula:

\[ \text{Capacity (Ah)} = \frac{\text{Energy (Wh)}}{\text{Voltage (V)}} \]

If the energy is given in watt hours (Wh), simply divide it by the voltage in volts (V).


Formulas for battery capacity


Calculation with watt hours (Wh)


If the energy in watt hours (Wh) and the voltage in volts (V) are known, the capacity in ampere hours (Ah) can be calculated as follows:
\[ \text{Capacity (Ah)} = \frac{\text{Energy (Wh)}}{\text{Voltage (V)}} \]

Calculation with current and time


If you know the current (in amperes) and the time (in hours), you can calculate the capacity directly:
\[ \text{Capacity (Ah)} = \text{Current (A)} \times \text{Time (h)} \]

Example 1

If a device is operated at 2 amps for 3 hours, then the capacity of the battery is:
\[ \text{Capacity} = 2 \, \text{A} \times 3 \, \text{h} = 6 \, \text{Ah} \]

Example 2

If the voltage of the battery is 12 volts and the energy is 72 watt-hours, then the capacity of the battery is:
\[ \text{Capacity} = \frac{72 \, \text{Wh}}{12 \, \text{V}} = 6 \, \text{Ah} \]

The formulas summarized


\[\displaystyle Energy= Capacity · Voltage\] \[\displaystyle E= C · U\]


\[\displaystyle capacity =\frac{energy}{voltage}\] \[\displaystyle C= \frac{E}{U}\]


\[\displaystyle voltage =\frac{energy}{capacity}\] \[\displaystyle U= \frac{E}{C}\]



The unit of measurement for energy is watt hours (Wh) or kilojoules (kJ)

\[ 1\; Wh = 3.6\; kJ \]

The unit of measurement for capacity is milliampere hours (mAh) or coulombs (C)

\[ 1\; mAh = 3.6\; C \]

The unit of measurement for voltage is the volt (V)

Is this page helpful?            
Thank you for your feedback!

Sorry about that

How can we improve it?