Wire Gauge for Battery Shut Off

[BroRobin]

What size/gauge wire jumper should be used for the Battery to Battery shut off switch? I’m installing shutoff onto plastic battery box, I was thinking 1 foot long with either 8 or 6 gauge wire with 3/8 lugs on each end.
What’s your thoughts / opinions.

[NorCal Eagle]

You need to know what amps you're drawing and wire type you plan to use. I use and recommend this tool from Blue Sea.

Circuit Wizard - Blue Sea Systems

[BroRobin]

Thanks, I assume my amps is no more than 30 seeing I have a 30 amp Service TT. I know that’s AC power amps but the DC power can’t be more than this. Or am I missing something.
Any way, here is the results from the calculations table:
Attachment 1


So if that is in deed the case, a larger gauge wire can’t hurt or am I wrong in this assumption?

This is what I had in mind:

6 AWG Gauge Red + Black Pure Copper Battery Inverter Cables Solar, RV, Car, Boat 12 in 3/8 in Lugs https://www.amazon.com/dp/B01F2NEPOQ..._NdbrFbHWS4MXM

[Cavie]

Originally Posted by BroRobin

What size/gauge wire jumper should be used for the Battery to Battery shut off switch? I’m installing shutoff onto plastic battery box, I was thinking 1 foot long with either 8 or 6 gauge wire with 3/8 lugs on each end.
What’s your thoughts / opinions.

What are you trying to do with this "Wire Jumper".

[BroRobin]

As stated in OP. Install battery shut off. Jumper goes from battery to 1 post of switch and main DC lead goes on other post of switch.

Battery Disconnect Switch with Keys, 6V 12V 24V Battery Kill Switch for Marine Boat RV ATV Car Auto Truck Vehicle, Waterproof Battery Master Switch, 200/1000 Amps, On/Off https://www.amazon.com/dp/B07MTYX5Z5..._FAbrFb2DR5DEQ

[Cavie]

Originally Posted by BroRobin

Thanks, I assume my amps is no more than 30 seeing I have a 30 amp Service TT. I know that’s AC power amps but the DC power can’t be more than this. Or am I missing something.
Any way, here is the results from the calculations table: Attachment 62745
Attachment 1
Attachment 62746

So if that is in deed the case, a larger gauge wire can’t hurt or am I wrong in this assumption?

This is what I had in mind:

6 AWG Gauge Red + Black Pure Copper Battery Inverter Cables Solar, RV, Car, Boat 12 in 3/8 in Lugs https://www.amazon.com/dp/B01F2NEPOQ..._NdbrFbHWS4MXM

Battery 12 volt amps and shore power 120 volts are two different things.

[BroRobin]

Originally Posted by Cavie

Battery 12 volt amps and shore power 120 volts are two different things.

WELL AWARE OF THAT.

The main DC line from batteries to Trailer is far less/smaller than 6 or 8 gauge wire.

I’m NOT, dealing with the 120 volts, just using total amps as reference for determining DC wire gauge needs.

Thanks for your input.

[Cavie]

Originally Posted by BroRobin

WELL AWARE OF THAT.

The main DC line from batteries to Trailer is far less/smaller than 6 or 8 gauge wire.

I’m NOT, dealing with the 120 volts, just using total amps as reference for determining DC wire gauge needs.

Thanks for your input.

Main line from battery ABSOLUTELY should be minimum #8 wire ga. Mine is factory #6 GA. A seconded set of wires would be #12 feeding the trailer breaks emergency brake controler.

[pconroy]

Originally Posted by BroRobin

WELL AWARE OF THAT.

I'll admit when I saw your 30A post I too had to go back and re-read. So, unlike the Ford battery on engine start, you'll likely never see a huge amp draw?

While for a run that short, the calculator will show 12 or 10AWG, I don't think there's a reason to NOT go bigger. I'd do 8, 6 or whatever's on the battery already.

Stranded too would be my guess.


Edit - I like those ones you found on Amazon!

[BroRobin]

Thanks for the input, as I stated in my opening post, I was considering either 6 or 8 gauge wires with 3/8 lugs on both ends.
I should be good to go with the 6 gauge wire.

Also considering DC amp draw the main fuse on the line leading from battery to All 12 volt circuit is a 30 amp rated fuse.

[Cavie]

Originally Posted by BroRobin

Thanks for the input, as I stated in my opening post, I was considering either 6 or 8 gauge wires with 3/8 lugs on both ends.
I should be good to go with the 6 gauge wire.

Also considering DC amp draw the main fuse on the line leading from battery to All 12 volt circuit is a 30 amp rated fuse.

There already is an inline 30 amp fuse. Look under the tong. It will be within 6' of the battery. May be in a box.

[BroRobin]

Originally Posted by Cavie

There already is an inline 30 amp fuse. Look under the tong. It will be within 6' of the battery. May be in a box.

That’s what I was stating. [emoji41] I think you and I are just a few paragraphs apart on the same page. [emoji1]

Thanks for all the input, anyway.

[RichCarter]

If the wire is short, you probably can use 8AWG wire. The battery box may not be the best place to put your switch. The box may not stay dry. Moisture may get into the switch and cause problems.



I just finished installing a cutoff switch purchased from Harbor Freight in the panel between my power converter/breaker box and my undersink storage. In my case, there was a wood panel that was in the way. It hid the water pump under the sink. I removed the panel and put two panels in the back of that locker to make room on the bulkhead to mount the switch. See photo, sawdust still on the floor. The switch is wired in series with the battery wire that runs behind the breaker panel and connects to the battery terminal on the converter. You'll need a pair of heavy gauge crimp ring terminals for this.

[01tundra]

Same size as your current battery cable.

[NorCal Eagle]

Check for any existing breakers on the main battery line to the TT and find out what amperage. On mine, it had a 50amp breaker feeding the DC side of the trailer. I used that as a starting point and went a little oversize on the battery cables. Won't hurt to go larger gauge.

I like to use welding cable because its so flexible (many strands of thinner copper vs fewer thicker strands) and typically very durable. Amazon carries some, but also check out this supplier: Wire & Cable Your Way

Edit - Looks like you're on the right track and identified the 30amp main fuse.

[Gazoo]

I just installed mine. 4AWG was way overkill. 8AWG was fine.