Battery cut off switch question

amxpress wrote:
Distance shouldn’t matter. Mine is 6’ away from my battery.

You can debate if 6' is close enough but you do want it close to the battery.

A long length of wire opens the opportunity for shorting out between the battery terminal and the disconnect.

If you turn the disconnect on the positive side to "off" and the cable between the battery and disconnect chaffs thru on a piece of grounded metal...zap.

Mounting it close with a short run reduces that chance.

If placed in the negative/ ground
And is in the disconnect is being use
Then the ground path is broken , there will be NO zap

Positive is the common most used way,
But a single cable ground offers advantage , if you have several cables on the positive terminal

2edgesword wrote:
I used what is technically a circuit breaker on the negative battery wire close to the battery. Its rated for 30amps and I’ve had no issues with it. I hit the switch and the battery is disconnected from the trailer circuitry.

And there's absolutley nothing wrong with doing it that way.

I used what is technically a circuit breaker on the negative battery wire close to the battery. Its rated for 30amps and I’ve had no issues with it. I hit the switch and the battery is disconnected from the trailer circuitry.

Old-Biscuit wrote:
Placed on NEG/ground....then if working on something and POS comes in contact with a ground ----ZAP

Placed on POS....you can touch wires, make contact, screw up.....NO ZAP

Fuses on POS
DC Circuit Breakers on POS
AC Circuit Breakers on LOAD (hot side)
For good reason and ALL are placed close to source of power

If the circuit is open, there’s no ZAP. Once the battery negative is no longer connected to ground, ground ceases to matter...it’s just a large chunk of conductor.

The reason fuses and breakers are on the positive is because the grounds are common so you have no other place to install them per circuit.

Some of the confusion about pos or meg mattering comes from the proper notion of disconnecting a car battery ground first. That is because a slip of a wrench against a nearby grounded frame won’t create a welder. Once the negative is removed, then the positive no longer can make a complete circuit if the wrench slips there.

On a cutoff switch, it doesn’t matter though the positive side can make more sense if there are any circuits (like trailer breakaway) that must stay connected and use a frame ground.

Placed on NEG/ground....then if working on something and POS comes in contact with a ground ----ZAP

Placed on POS....you can touch wires, make contact, screw up.....NO ZAP

Fuses on POS
DC Circuit Breakers on POS
AC Circuit Breakers on LOAD (hot side)
For good reason and ALL are placed close to source of power

Functionally, it can be put on either side and anywhere before the load.

Blazing Zippers wrote:
All along, I've been under the impression that a cut off switch should be placed close to the battery and on the positive side of the system. Is this right?

In general I agree.

A master fuse or circuit breaker or similar overcurrent protection needs to be near the battery on the positive side to protect the wiring in case of a short circuit (and hopefully prevent a fire).

A cutoff switch may be anywhere that makes sense electrically and physically for whatever you're shutting off. Obviously, if it's also serving as the circuit breaker then that constrains where it ought to be. Traditionally switches are placed in the positive wire, which under some circumstances can have a few advantages for things like working on the wiring system, as it tends to have fewer things live when shut off.

Distance shouldn’t matter. Mine is 6’ away from my battery.
The factory also installed it on the ground/negative side.