How to Measure Internal Resistance?

[A123rc]

How to measure Internal resistance ?
As the resistance of a battery provides useful information about its performance and detects hidden trouble spots, I want to know how to measure internal resistance!

[pebe]

Connecting a load on to a battery will result in a fall in battery voltage. So you can calculate internal resistance like this.

If you measure the battery voltage with no load, and then measure the battery voltage and current drawn when loaded, the internal resistance of the battery will be:-

Difference between the two measured voltages/current

[aadambell]

<expletive deleted> Never thought while studying High School Physics all those years back that explaining Internal Resistance would be such an arduous task!

“The internal resistance of a battery can be calculated from its open circuit voltage, voltage on-load, and the load current. An equivalent series resistance meter as used to measure the ESR of capacitors, essentially an AC milliohm meter, can be used”.

[pebe]

aadambell,
An ac milliohmeter can only measure impedance of a capacitor, which is not the same thing.

To measure ESR you need to separate the resistive component from the reactive component, so you need a bridge or some way of measuring the impedance and its phase angle.