The Stovebolt Site Forums The Shop Area The Electrical Bay Battery cable resistance

Lots of good info about wire here.

The way I test battery cables is to measure the voltage drop across the cable.

Put the plus lead on the positve terminal of the battery and the minus lead on the power stud on the starter. Assuming a fully charged battery, when the motor is cranking the meter should read at least 9 volts if everything is happy.

If its lower you need to check pieces of the circuit to find the problem. Think of the electrical circuit as a loop made up of connections to each part of the circuit and going from the positive post on the battery to the negative post.

Keeping the plus lead closest to the postive post on the battery check the voltage drop across each connection. Start with the plus lead on the battery post itself, and the negative lead on the connected connected to the plus terminal at the battery.

With the meter connected check the voltage drop. Its been years since I read what values you are looking for, but my rule of thumb for the starter circuit is that any drop of 1-volt or more is probably an issue.

If the voltage drop is between the battery and the connecter on the cable, you may be able to clean things and make it work better. If the voltage drop is in the cable itself, either the cable is too small, or its too corroded to work.

I generally start by measuring across several things to narrow down where the problem is, and then measure each piece within a segment to identify the specific issue.