# How to calculate wire gauge when connecting battery cells in series?

How does one determine what wire gauge to use when building a battery by connecting lower voltage cells in series?

e.g. Let's say one is building a couple of 12V batteries that are expected to supply 100 amps continuously. The first battery is composed of eight 1.5V cells. The second is composed of two 6V cells.

Using a wire gauge table I've determined that one will need a 4 AWG cable 6' or less in length to handle 100 amps with <3% voltage drop.

What gauge wire should be used to connect the cells from the examples above in series? Should the internal cables also be 4 AWG? Do the number of cells and their respective voltage matter?

Current is all that matters - until the voltage gets high enough that insulation breakdown becomes a concern.

Use the same gauge wire in the battery link as you're using in the main circuit.

The first battery is composed of eight 1.5v cells. The second is composed of two 6v cells.

This sounds like a bad idea. I have never heard of 6 V (capital 'V' for volt) cells but it suggests that you are mixing battery chemistries and these will have different discharge rates and capacities.

• Thank you. I didn't know it was case-sensitive. In this case the cell voltage is arbitrary and theoretical. I wanted two distinct contrasting examples.
– Tag
Commented Nov 27, 2020 at 7:46
• This leads me to the conclusion that fewer cells are better simply because it'll take less material to connect them.
– Tag
Commented Nov 27, 2020 at 7:52