Battery Disconnect on Pos or Neg side?

[Chris J]

I purchased and installed a battery disconnect on my M327. I read this AM that it should be installed on the low (neg) side rather than the high (pos) side. I had already installed it on the Pos side. Will it matter?

[mbopp]

No, but installing it on the negative side is safer - no sparks if the wrench contacts metal.

[howson]

I purchased and installed a battery disconnect on my M327. I read this AM that it should be installed on the low (neg) side rather than the high (pos) side. I had already installed it on the Pos side. Will it matter?

If you check out the diagrams in AMSolar's archives, every drawing that has a battery disconnect shows it connected to the positive side of the battery. https://drive.google.com/drive/folde...C1YbLzdNrrT32E

I'm sure one of the electricians that frequent the forum can explain "why".

[Jkwilson]

It doesn’t matter electrically. As mbopp said, it reduces the chance of a wrench (or anything else conductive) shorting the battery If it’s in the negative.

Many people operate on the mistaken idea that current flows out of the positive terminal of the battery and that interrupting it there is best. In reality, current flows out of the negative post and it doesn’t matter where you interrupt it.

[Jkwilson]

Depends....on whether you subscribe to the "current flow" theory......or the "hole flow" theory!

Seriously though, it probably stems from the standard of where to put a switch in the 120VAC side of things. You always switch the "hot" lead and never switch the neutral lead.

The carryover may very well be from AC 120V wiring.

In engineering school, I had a physics professor who forced us to use actual electron current flow directions and polarity rather than the conventional current flow used in every other class I took. Kind of like have your steering wheel work backwards for a few hours a day.