# Dual Battery Disconnect



## Rookie (Jun 29, 2009)

I replied to a different post but thought I would start a new one so not to get lost in the 3 pages of replies. Here is what I posted:

I might know the answer but when messing with electrical (which I know nothing about) I want to be sure. I bought the following switch:

http://www.campingworld.com/shopping/item/top-mount-safety-switch-with-wing-nut/1311

I have a dual 12V battery setup as the image I attached shows.

So I should mount this switch on the negative post on the battery which grounds to the trailer? I was thinking to mount it to the negative post, then use the wing nut to connect my ground to the trailer and the negative which goes to the other battery. Is that correct? Thanks.


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## Nathan (Jan 2, 2007)

Yes, go ahead and do that.


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## thefulminator (Aug 8, 2007)

That is the way I did mine.


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## hautevue (Mar 8, 2009)

Yes. The lug with the bolt goes on the negative battery post. Take all the white wires (white = ground = minus) and put them under the wing nut on the knife blade side of the switch.

Then, when you open the knife blade, you break the ground connections.

I have this on my TT and have learned the following:

1. The knife blade type of switch, which both of us have, is relatively high (height, not price). Thus the battery cover will not go down all the way. I just made sure to drill a few holes in the bottom of the battery boxes so water will drain out, put the covers on as best I could, and snugged them down with the strap. The other solution is to buy the flat green cutoff switch from someone---it's lower than the knife switch device.

2. My electric jack: I decided that I wanted to be able to raise or lower the TT without having to unstrap the battery cover, turn the knife switch on so the ground lines are connected, and then reverse the procedure after finishing. The electric jack is grounded, through the case/bolts on its bottom, to the frame. Works fine, but not if the ground knife switch is "open". So I put a #12 wire with a ring on one end, under one of the jack mounting bolts, and put the other end directly on the battery negative post. Thus the jack works always, regardless of the knife switch position.

But the knife switch system works nicely, and the sneaky load (CO detector, propane detector, Jensen stereo, etc.) doesn't drain the batteries.


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## Rookie (Jun 29, 2009)

hautevue said:


> Yes. The lug with the bolt goes on the negative battery post. Take all the white wires (white = ground = minus) and put them under the wing nut on the knife blade side of the switch.
> 
> Then, when you open the knife blade, you break the ground connections.
> 
> ...


Thanks for the information! For some reason I thought you would connect it to the positive and cut off the trailer from the batteries, but the switch says to connect it to negative which made me wonder. I also read some other posts which said to hook to negative versus positive as well. I really don't know much about electricity so everyone's information is extremely helpful. Thank you all again for taking the time to reply to me, it is MUCH APPRECIATED.

I didn't think about the covers. Since I already have the switch I think I'll just make it work and drill some holes of my own. If it becomes too much of a pain I'll invest in a smaller switch.


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## thefulminator (Aug 8, 2007)

With you switch in the off position, the positive is connected to your switch and you accidentally drop something that shorts between the positive and the frame you get lots of fireworks. If the switch is on the negative and you short between the positive and the frame, nothing happens because there is no circuit created.


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## AKF150LARIAT4X4 (Sep 14, 2005)

This is what I have on my TT. I took a dremel tool and cut out a rectangle on the battery case lid for the switch to go down into. I then used the mounting holes and mounted it to the battery case. I just did it today and forgot to get pics. Pics tomorrow.


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## AKF150LARIAT4X4 (Sep 14, 2005)

This is what it looks like under the lid...









Top view with cap on to keep out rain.









Side view with cap on.









Angled view with key inserted.









I didn't cut the hole perfectly so I need to put some RTV from the inside just to seal up a little gap.


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