[AdamIsAdam]

Silly question, but is this simple type of battery disconnect supposed to be connected to the Positive or Negative terminal on the battery? I'm reading all the near fatal fires/shorts/melting wire issues and thinking that it should be connected to the positive terminal and unscrewed as often as is convenient and practical to be on the safe side. Right?

http://www.summitracing.com/parts/hfm-batktw/overview/

[rad400]

Negitive that is where mine is about 3 years.

[David Jones]

Positive on mine for about a decade.

[Skip Fix]

When the Camaro was an autocross car it was on the negative side also for 10 years.

[Firebob]

Mine is on the pos because in the case of needed disconnect you may be grounding somewhere else even though the cable is disconnected from the battery. Say if something had fallen onto the batt or if the batt broke and became unattached.

[JSPONT]

Originally Posted by Firebob

Mine is on the pos because in the case of needed disconnect you may be grounding somewhere else even though the cable is disconnected from the battery. Say if something had fallen onto the batt or if the batt broke and became unattached.

^^^^this^^^

[Chris65LeMans]

I vote positive. Removing the negative terminal won't do any good if the battery finds somewhere else to ground.

[AdamIsAdam]

I'm going to switch mine over to Pos... as soon as I put the battery back in the car

[60man]

Originally Posted by Chris65LeMans

I vote positive. Removing the negative terminal won't do any good if the battery finds somewhere else to ground.

Right on !!
Or any other ground wire !!!

[nytrainer]

Adam
Here's my on this matter. I assume you are using a top post design battery (not side posts). If you were to measure the inside diameter of the battery disconnect device (where is mounts to the battery post) and the outside diameter of the post on the battery disconnect device (where the battery cable gets re-attached) you will see the diameter of these two points are slightly smaller then the negative battery post and the negative battery cable. The battery disconnect device will NOT fit over the positive post without distorting it and the positive battery cable will be too large to "clamp" on the post of the battery disconnect device. That fact alone convinced me what battery post the disconnect should be on.
That said I have these devices on the negative posts of my two cars.
Here's another "plus" (see what I did there? lol) for using the disconnect on the negative terminal..

Scenario # 1 If the disconnect device is mounted to the Pos. terminal than all grounds still return to the battery via grounds straps etc.. IF you accidently touch the positive terminal with a tool, keys, whatever and bridge across to the fender or any other metal parts then be ready for nice shock or at least a mini fireworks display. This is 1000 times more likely to happen than "the battery finding somewhere else to ground"

Scenario # 2 If the negative post has the disconnect device there are NO grounds back to the battery and if you bridged the positive post to the fender etc.. NOTHING would happen as there is no circuit path back to the battery.
By the way, this thinking goes along with the reason why you ALWAYS disconnect the negative terminal first when changing a battery and ALWAYS put the negative terminal on last when re-attaching. That reason being is because once you disconnect the Negative terminal you can safely remove the Positive without worrying that the tool you're using will touch metal as you undo the clamping bolt.

[JSPONT]

I could tell you a story about that, okay I will, I had a twin turbo Porsche I build with a Rennegade kit. Put it together, forgot to add ground straps. One day I connect the positive cable to take it for a ride, get in the car and start to crank it. I noticed it was cranking slow, when I got out of the car, I saw a small fire. I opened the lid put out the fire. The car grounded thru the ground strap of the Msd ignition box. A $350.00 mistake. Added 3 ground straps after that not a problem. I always dis connect the positive.

[JSPONT]

The reason track cars disconnect the positive beacuse it shuts everything down. No chance of the fuel pump or ignition running with out power.

[60man]

I don't really like that kind of disconnect. It's OK to safeguard your car when stored...
But if you get a big dead short things get very hot in a hurry...making it hard to touch...
that's why wires burn!!!
JMO...

[nytrainer]

Originally Posted by JSPONT

The reason track cars disconnect the positive beacuse it shuts everything down. No chance of the fuel pump or ignition running with out power.

Ummm, there would be no power through those devices either without a return path to the battery negative post.
Either way (neg or pos disconnect) opens the battery circuit but as the OP asked "what terminal does the battery disconnect go on" he was referring to the device's picture he posted. That's why I gave the answers I did.

[Tom Vaught]

I just disconnect the ground cable with a simple box end wrench, put a PCV "cap" over the negative post, and call it a day. The negative post is totally protected from seeing a ground to the body or wiring so the positive cable cannot make a circuit.
The ground cable terminal drops below the level of the top of the battery.

Switches sometimes fail in a "On" position or get left connected by people forgetting.

If you have an open circuit to the Negative post on the battery, impossible to complete a circuit to the battery.

Tom V.

[nytrainer]

Originally Posted by Tom Vaught

I just disconnect the ground cable with a simple box end wrench, put a PCV "cap" over the negative post, and call it a day. The negative post is totally protected from seeing a ground to the body or wiring so the positive cable cannot make a circuit.
The ground cable terminal drops below the level of the top of the battery.

Switches sometimes fail in a "On" position or get left connected by people forgetting.

If you have an open circuit to the Negative post on the battery, impossible to complete a circuit to the battery.

Tom V.

Even better and cheaper too. Cap on the negative post is genius too.

[george kujanski]

what nytrainer said. With NO cable connecting the negative post to the car's metal, dropping a metal tool, etc. onto the positive post and car metal will do no damage, nothing. On the other hand, disconnecting just the positive post still provides a path for a short if a wrench, etc falls on the positive post to ANY metal.

In the case mentioned how the MSD box provided a ground...impossible. If there was no connection back to the battery negative post, that could not happen, therefore the neg post was not totally disconnected.

I vote for disconnecting the negative post....that's what I do.

George

[AdamIsAdam]

So if a short started, like the two threads I read earlier today (one of them being NYtrainer's experience) and all of a sudden the car started smoldering, burning the main POS wire going to the starter, for example, and I ran over and unscrewed the negative using the part pictured above, then I would stop that melting of wires instantly? (assuming it's not actually on fire yet, but just melting the insulation)

Maybe two disconnects should be used

[Region Warrior]

Whenever having to do most any electrical repair/replacement, GM's 1st instruction is;

Remove negative battery cable.

[Tom Vaught]

If the BATTERY NEGATIVE TERMINAL has no connection to the vehicle wiring or chassis then it is impossible for the battery to conduct electrons thru the wiring.
Electrons travel from the negative post to the positive post.

Tom V.