Jumper for Batterys in Series

Unbundled #10 is good to 60 amps. Still if the OEM feed is #6 I would make jumper the same.

I don't want to belabor the point, you're going to do whatever you think is needed, as you should. But just to add to the discussion...

Instead of comparing the series jumper size to the primary cables size, consider the cable size needed to handle the maximum current draw. The primary cables in the OP's pic are oversized for some reason. Not sure why, but there is no reason why the jumper has to match those.

The pic below shows the factory wire size in my fifth wheel. My converter is a 55a, so the wiring was designed to handle that, and the converter is on the far end of the coach, about as far away from the battery bank as it could be. No issues with wire size. It all works fine, as designed.

Needs to be cleaned up (all of them), but the size is not going to be an issue. The OP asked about size.

I should say, I'm assuming those are house batteries since they are 6v. If it were starting batteries, which need to supply high amps, then it would matter.

The terminal on the lower left needs a wing nut. :)

bpounds wrote:
Replacing that cable would just be a waste of money. Real world, there will be zero benefit. At least it isn't very much money, and maybe it will make you feel better. Which is a benefit in itself, but isn't very much benefit.

Could you take a look at the picture again, please, and confirm that you see nothing wrong with that jumper cable?

A #2AWG jumper cable with well attached lugs should be about $5.

bpounds wrote:
(clip) At least it isn't very much money, and maybe it will make you feel better. Which is a benefit in itself

:C:B:B:B:B YEP I feel better already...........

Replacing that cable would just be a waste of money. Real world, there will be zero benefit. At least it isn't very much money, and maybe it will make you feel better. Which is a benefit in itself, but isn't very much benefit.

naturist wrote:
Actually, I believe you'll find that because the red jumper is so much shorter than the wires going to the converter/load, it can stand to be smaller in diameter. This effect is why extension cords need to be bigger as they get longer.

X-2
Also after cleaning the corroded cable with baking soda and water put some dia-electric grease on them.

Dusty

That battery setup is in need of better termination and replacing the jumper with the correct size would be my suggestion. Applying a film barrier to the terminals (even grease helps) will eliminate a lot problems going forward.

The reason for using large wire for the battery connections is to reduce the voltage drop. Since the jumper wire is usually much shorter than the others, a smaller wire will have a much smaller voltage drop than the other wires so it's size is less important than the longer wires.

Of course, all the wires must have a current carrying capacity adequate for the highest current the batteries will see, either charging or discharging.

I use a number 6 or 4 wire for that job