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.
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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)
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