Calculating a Battery's Internal Resistance

[Sephiroth]

Hi Everyone,

Does anyone know a good method for calculating a battery's internal resistance?

I don't suppose it could be as simple as getting two identical batteries (equally charged) and then hooking the positives together and measuring the resistance across the two negative terminals and then dividing that figure by two

That would make my 24ah batteries 3 ohms by the way but I doubt that is an accurate test

[mlindeblom]

Chapter 9: Internal Battery Resistance has a good howto