I would like to add some sort of battery disconnect device on my truck for when I'm working on it. Do the batteries come together anywhere and share a negative cable or will I need two disconnect devices at both batteries. I know unplugging one doesn't disconnect the other, that just disables the one battery.

 

If I remember, theres a red lead comming from the fender solenoid which brings power to the batteries. Batteries are bridged so you only need to disconnect the one battery to work on the truck. Theres two big cables that come off the stock positive terminal. One goes down to the starter, and the other bridges over to the positive terminal on the drivers battery.

The front, positive terminal you can see the smaller red lead wire. I am pretty sure it was fused into the stock terminal clamps



http://smg.photobucket.com/albums/v6...1310336042.jpg



personally I wouldnt bother putting a "device" to disconnect the power because that device will be prone to fail eventaully. Just disconnect the passanger terminal. You could run your power off a switch like you want, but it wont be cheap. I have a portable 9000lb winch that draws 450 amps at a full pull. It cost me well over $200 just to wire it, and another $200 for a 1500 watt, 500watt continous duty solenoid, which is the biggest they make. For the amount of time I actually use the winch I didnt want to have power running to the bumper at all times, but also didnt want to pop the hood and connect the positive.

 

I was looking at boating battery disconnect switches to get the terminology I needed to find something powerful enough to handle up to 2000 starting amps. It might be best to have one for each battery, because of the power rating. [LINK] You should also have an alternator field disconnect on at least one of the switches. Disconnecting all batteries with the engine running and without putting the alternator to sleep can fry the alternator. I've heard of one member pulling both batteries on his 7.3L while running to dash into the autoparts store to get two new ones - without harming the truck. I wasn't there and I have great difficulty believing it went as described.

 

Battery Switch - Harbor Freight Tools

 

I would use a disconnect like this Item # 51-918, Battery Master Disconnect Switches on Pollak

These are the style disconnects that are used on large equipment such as dozers, excavators, etc. All the large equipment disconnect the negative cable. I have seen these disconnects 30+ years old and still working just fine. The specs say they are good for 1000 amps but I have seen many machines running 4 batteries in parallel through a single disconnect.

I would actually use 2 of them, one on each negative battery cable.

 

What about a welding lead disconnect. They are available in many sizes.
I use them to power my winch.

 

The negative cables are independent of each other and bolt to the front of the block on either side. The positive cable as you know goes from the drivers side to passenger side, then splits in two. The large gauge goes directly to the starter and the smaller one goes to the solenoid on the passenger fender.

In theory, you'd only need a disconnect on the smaller positive wire since the large one is only for the starter. I'd be a little paranoid about disconnects on the negatives due to the high amperage flowing through them when the starter is engaged.

 

That is a great idea. I might just put a set of these on http://www.amazon.com/Hobart-770033-.../dp/B002AKIREY

It would be a great time to switch to 0 or 2/0 welding cable for the negative cables at the same time.