# How do you calculate the internal resistance of a battery?

##### 1 Answer

A real-life battery can be described as an ideal voltage source with an internal resistance.

If you measure the voltage of a battery with a Volt-meter, which has a very high resistance, you'll get the raw voltage.

If you add a smaller resistance between the poles of the battery, you will see that Ohm's law is not followed, but the amperage is lower than expected.

**An example**

Raw voltage:

Measuring the current with a

In reality we measure

Therefore the **total resistance**

So the **internal** resistance of the battery in this case:

**Extra**

You can also work with the voltage loss on the poles of your battery. I'll leave that to you.