I'm calculating the size of wires that I need in my van conversion, and I stumbled upon an issue that I can't find the answer to.

To my question: How many amps will flow through the cables between my batteries if I have 2 batteries wired in parallel?

Let's look at a simple example:

[![enter image description here][1]][1]

We've got 2 batteries in parallel, and one 12v lamp that requires 3 amps. The wire from the battery to the lamp will require a wire that can handle 3amps, but how many amps will go through the cables between the batteries in this example?


  [1]: https://i.sstatic.net/qobsV.png