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Old 12-03-2011, 07:59 AM   #1
31chevy
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Default battery disconnect switch.

What do most of you prefer when using a battery disconnect switch ? The ground side of battery or hot side. I realize that either side isolates the battery but would like to hear your preference & why. Thank you in advance.
Gary.
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Old 12-03-2011, 08:17 AM   #2
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Default Re: battery disconnect switch.

Negative per instructions given with the dis-connect.

Last edited by toby; 12-03-2011 at 08:18 AM. Reason: Reasom
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Old 12-03-2011, 08:33 AM   #3
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Default Re: battery disconnect switch.

It really doesn't matter which side is disconnected. I have had at least 3 of the ones with the green knobs fail. They are cast aluminum gold colored and do not give full power after a while. Bob Shewman gadgiteer@aol.com provides a heavy duty disconnect that give full power with no drop and should last forever. These are specified for use on hospital emergency vehicles. G.M.
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Last edited by G.M.; 12-03-2011 at 06:41 PM.
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Old 12-03-2011, 08:45 AM   #4
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Default Re: battery disconnect switch.

I think the negative side disconnect is for negative ground systems.

When you disconnect the battery, it is safer to disconnect the ground side (first). If your wrench would hit something grounded as you loosen the nut, no sparks fly. But if you disconnect the ungrounded side and the wrench hits a ground, you cause a battery short.

With the grounded side disconnected, dropping anything on either the positive or negative terminals (but not both) won't cause a short. It's unlikely but if you want to choose one, this is the choice.
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Old 12-03-2011, 09:07 AM   #5
JM 35 Sedan
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Default Re: battery disconnect switch.

Use one of the good heavy duty snap action switches designed for this application and sold by many automotive parts suppliers. The best recommendation is to break/open the ground side connection.
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Last edited by JM 35 Sedan; 12-03-2011 at 09:49 AM.
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Old 12-03-2011, 09:27 AM   #6
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Default Re: battery disconnect switch.

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Quote:
Originally Posted by G.M. View Post
It really doesn't matter which side is disconnected. I have had at least 3 of the ones with the green knobs fail. They are cast aluminum gold colored and do not give full power after a while. Bob Shewman gadgeteer@aol.com provides a heavy duty disconnect that give full power with no drop and should last forever. These are specified for use on hospital emergency vehicles. G.M.
GM , have you posted wrong email on Bob again? it bounced back on me,think this is one of those "Deja Vu all over again" moments
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Old 12-03-2011, 09:30 AM   #7
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Default Re: battery disconnect switch.

Mine was on the negative side until yesterday when it quite. I was having trouble starting in the cold, slow cranking, and I took it out. It start cranking much faster without the disconnect in. I am looking for a more reliable unit, any ideas?

Bill
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Old 12-03-2011, 10:43 AM   #8
Fordestes
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Default Re: battery disconnect switch.

we always put the switch on the chasis ground ,without a ground one can even accidentally short to the non ground and not have a problem when the circuit is interrupted at the chasis side, flaming river makes a good heavy disconnect , we used them for years on trucks and heavy off road equipment also they have an optional lock out bracket.
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Old 12-03-2011, 11:28 AM   #9
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Default Re: battery disconnect switch.

Quote:
Originally Posted by 31chevy View Post
What do most of you prefer when using a battery disconnect switch ? The ground side of battery or hot side. I realize that either side isolates the battery but would like to hear your preference & why. Thank you in advance.
Gary.
First, avoid the crappy green knob post-style switches. The best are HD inline rotory remotes made by Cole Hersee, Moroso, etc, and those with alternator connections are designed for positive + battery switching (For negative - ground systems). NHRA also requires positive + switching, and that's how all my battery switches are wired. Do some research and you'll find most recommend switching the positive + side. IMO.

Last edited by V8 Bob; 12-03-2011 at 12:28 PM.
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Old 12-03-2011, 11:35 AM   #10
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Default Re: battery disconnect switch.

Quote:
Originally Posted by 37 Coupe View Post
GM , have you posted wrong email on Bob again? it bounced back on me,think this is one of those "Deja Vu all over again" moments
It's gadgiteer@aol.com.
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Old 12-03-2011, 12:14 PM   #11
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Default Re: battery disconnect switch.

I don't like the looks of the green knob type switches that attach to the battery terminal. As others have mentioned, my experience with them is that they burn or pit as well. I prefer rotary type, bulkhead mounting switches that I can hide. You get what you pay for on these as well. The cheapies tend to fail pretty quickly.
I was in a hurry to get a switch installed and went to my local NAPA store. The only one that they had in stock was an expensive one. Bought it because I wanted to get the job done that day. You could feel the difference. The switch was much more positive than the cheaper versions. That switch has been working flawlessly for three years now and engages just as well as it did when I installed it. The model number was SW29. It will give you sticker shock however.
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Old 12-03-2011, 01:17 PM   #12
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Default Re: battery disconnect switch.

Napa sw29 + $84.99
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Old 12-03-2011, 01:37 PM   #13
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Default Re: battery disconnect switch.

Put it in the ground cable. That way nothing is hot. If you put it in the hot cable the hot post on the battery as well as the terminal on the back of the switch is still hot.
Either way will break the circuit but the ground cable is the best/safe way!
Bill
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Old 12-03-2011, 02:00 PM   #14
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Default Re: battery disconnect switch.

I know a lot of you are going to think or say "$84.99, holy crap thet's too much. $84.99 might seem like a lot, but it could save your vehicle, and it's probably less than you spent for the last little "widget" that you bought to finish it. And that "widget probably had nothing to do with safety or operation of the car. Now, if it's at night that something happens and your car is in the garage/shop -------------, and your garage shop could be attached to your house----------------- and your family could be sleeping in the house-------------------

Pretty cheap insurance if you ask me.
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Old 12-03-2011, 02:13 PM   #15
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Default Re: battery disconnect switch.

I don't know what is really best but I have been putting my disconnect switch in the positive line with the switch normally on the floor of the vehicle slightly under the front edge of the passenger side seat since the early 70s. A HANDY inside switch can do wonders for your piece of mind when you car starts smoking while driving down the road and the alternator suddenly cooks! I switched it off, the wife stopped getting excited, and we coasted to a driveway and got off the road.

Put the sw where you can get to it NOW! if necessary.

JMO.... and the wife's!

Hamtown
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Old 12-03-2011, 02:16 PM   #16
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Default Re: battery disconnect switch.

So it seems the majority favor putting them on the Negative side, which seems to make sense to me but is the opposite of what the NHRA requirements are (it seems like they should know). Any more insight??
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Old 12-03-2011, 02:38 PM   #17
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Default Re: battery disconnect switch.

I think (pretty sure) that the NHRA position is that if you try to kill the engine in an emergency by disconnecting the battery, the output from the alternator or generator will continue. The engine will keep itself running as long as the ignition switch is on. I use a switch on the ground side just to make sure that the car is dead when it's parked/stored and I only disconnect it when the engine is already off.
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Old 12-03-2011, 04:17 PM   #18
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Default Re: battery disconnect switch.

Quote:
Originally Posted by Randy in ca View Post
So it seems the majority favor putting them on the Negative side, which seems to make sense to me but is the opposite of what the NHRA requirements are (it seems like they should know). Any more insight??
You may have misunderstood what you read in some of these posts. Negative (-) does not necessarily = ground. My cars are stock 6V positive (+) ground and I put the cutoff switch in the ground or positive (+) side. Now if my cars were connected negative (-) ground I would still put the cutoff switch in the ground side which in this case would be negative (-) ground. Remember that ground does not always = negative (-).
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Old 12-03-2011, 04:32 PM   #19
Jack E/NJ
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Default Re: battery disconnect switch.

Disconnect the ground whether it's positive or negative, for the reasons explained by PeteVS above.

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Old 12-03-2011, 06:13 PM   #20
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Default Re: battery disconnect switch.

I like the rotary master switches with the removable lever. Whenever I leave the car the lever goes with me.

Every little bit of security helps.
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