Battery wiring.

[Mollysdad]

I'm half way through a mod for my batteries, and I keep seeing this mentioned in posts. (assume parallel wiring)
"When wiring batteries, put the positive on battery 1 and the negative on battery 2 to equalize the load."

But wait, the two batteries are connected together by jumpers of large gauge. Those jumpers are there 24/7; why can't the batteries equalize themselves? It's not like one will be 11 v and the other 13 v. They're paralleled!

Is it so the electrons flow through both batteries on their way to the load? Rather than get sucked out of one battery and replaced from the other? I would think this is instantaneous.

[rmkrum]

In any piece of wire, there is some resistance. It’s usually very small, on the order of milliohms. This causes a tiny voltage drop when you charge or discharge a battery.

The reason for the wiring directions you quoted is to equalize this tiny voltage drop so the individual batteries see essentially the same voltage. This is done in an attempt to keep the exact same voltage, same current through each set of cells, and hopefully the same state of charge on both batteries in a parallel setup. Over time, a tiny voltage difference between two batteries in parallel can cause imbalance issues. This hookup attempts to minimize the problems, and is simply a “good engineering practice”.

That said, I’m an advocate of using honking big 6 volt golf cart-sized flooded batteries in series, and that way I’m effectively only dealing with ONE battery.