battery disconnect switch
 

I want to install a battery disconnect switch on my 47 car.
1. does it matter if it states 6-48 volt or 12-48 volt, will both work on 47 6volt system ?
2. what is the proper way to hook it up to a 6 volt positive ground system
3. what size cable should i use ? Thanks

Re: battery disconnect switch
 

This is assuming your car is still 6 volts, positive ground.

1. The 12 volt switch, even though it probably would work, is not even rated for your car, so why even consider it? Remember, 6 volt system require heavier components because of the greater amperage carried. Equivalent systems carry twice the amps as 12 volt systems.

2. I would put it on the negative (hot) side. That way all power to the car is cut off. Put it on the ground (positive), and everything still has power going to it.

3. 0 is OK, 00 is better.

Re: battery disconnect switch
 

The easiest way to go would be to just disconnect the battery cable from the battery.

Re: battery disconnect switch
 

Great advice indeed.

I would add, do NOT use one of those cheapy things that go directly on the terminal.

Re: battery disconnect switch
 

Hi tubman, thanks for advice on the 6volt. So one cable from the negitive post of the battery to the switch and one cable to ground on the firewall, but I have a positive ground system, I'm confused please set me straight.

Re: battery disconnect switch
 

The negative side is the "hot" side on a positive ground system.
If you disconnect that side, ALL power stops right at that point.
Tubman is sharp with this sparky stuff :)

To be clear, you need not do anything to the ground side cable.

Re: battery disconnect switch
 

Some controversy on what pole to put a disconnect on. Most advise to put it on the ground side (in your case the positive if an 6V car). Without a ground, as you may know, nothing electrical will work.


That said, I have always worked with 12V negative ground cars so maybe a 6V positive ground car may be different.

Re: battery disconnect switch
 

Think of your home... if wired properly, the lamp switches interrupt the "hot side". If the common side is interrupted, there can still be feed through. Much safer to interrupt the power supply.
A car is not much different, ya want to interrupt the "hot side". In the case of a stock '47 Ford, the "hot side" is the negative post.

Re: battery disconnect switch
 

And then, of course, there are electrolysis and corrosion considerations if you have power going through the car. (Probably not important if the vehicle is stored under ideal conditions.)

Re: battery disconnect switch
 

I've never been a fan of those things. They quite often result in problems down the road a few years with bad connections in an un necessary gizmo. Just pull off the battery cable. If its clean as it should be, its an easy thing to deal with.

Those things are popular with the model A crowd as that wire harness is hot all the time. Your 47 has a fuse , no? Sorry, I am not familiar with post war stuff

Re: battery disconnect switch
 

I used a marine grade Cole-Hersee Heavy Duty disconnect switch. Which meant its all brass. It fit neatly in one of the existing holes of the battery support brace. Which meant it’s a short run to the solenoid and the extra cable hides nicely appearing to be the same cable.

No holes needed to drill. Nice solid feel switch. Works much better than wearing out your battery terminals. Quicker and safer too.

Re: battery disconnect switch
 

I've had one of those "on-terminal" screw knob switches on my Corvette for at least the last 20 years with zero problems. I turn it on once a year and off once a year. Each time I cycle it, I take it apart and make sure it is nice and clean with no incipient corrosion. I guess even crap works if you take care of it. I did make sure that the one I had was all brass, however.

Re: battery disconnect switch
 

I have a Cole Hersee 2484-16-BXbBattery master disconnect switch mounted on my ;32 seat riser. Simple to access and I always shut it off with power shutdown.

https://www.fordbarn.com/forum/attac...6&d=1716373212

https://www.fordbarn.com/forum/attac...7&d=1716373212

Re: battery disconnect switch
 

I use the same and also located in the seat riser. Works great.

Re: battery disconnect switch
 

Re: battery disconnect switch
 

I have always used the Cole-Hersee switch. Never had a problem with them. As others have said avoid the one that uses the battery post.

Re: battery disconnect switch
 

You need to remember that if either side of the battery is disconnected you have a completely dead circuit. In that case it doesn't really matter which side the switch is on. What is possibly more important is where your switch is located and if the terminals are exposed to accidentally being touched by a tool or something. If it's on the ground side, you can't short it out. If that switch on the seat riser is on the hot side, one of those terminals is always hot and can be easily shorted to the body ground. I have one located just like this but put it on the ground cable. That's much safer in my opinion.

Re: battery disconnect switch
 

I agree, mine is on the 12V negative ground side.

Re: battery disconnect switch
 

My 47 is 6volt positive ground system. So I hook one cable from the positive post (ground) to the switch and one cable from the switch to ground ( firewall)
Is that the right way.

Re: battery disconnect switch
 

This is a pic of a switch I had on my 04 Dodge pickup, the culprit (or one of them) that is guilty of being a failure. I use the truck very little and suspect I have a parasitic drain (which I cant find) as well as the normal draw these trucks take when parked. The clamping area would constantly corrode and require filing it clean and flat to keep it working. On a side note, if it was working enough to start the truck it did not mean the truck would run well. It would sputter, cough and did not like throttle inputs at all. It took me a while to figure this one out. The second pic shows part of the switch body where the bolt makes contact to close the switch; I put bluing in the contact area to indicate how actual little contact area there is in the switch, amazing the truck would start at -30C. Buy a good switch.

Re: battery disconnect switch
 

Same

Re: battery disconnect switch
 

Completely agree with you. I have had problems with two disconnects so now all I do is have a 1/2 inch wrench in the car to disconnect the battery. Never wore out a terminal either.

Re: battery disconnect switch
 

+1 on the Cole-Hersee I think I bought mine off of eBay, I made sure it was an older one made in the USA.

Re: battery disconnect switch
 

My 2 cents on which post to use for the battery disconnect. Think about when you disconnect the battery. You disconnect the ground first. That way you don't accidentally touch the hot cable to a ground source when disconnecting the hot cable with the ground still connected. JMO


Edit: but some sanctioning bodies specify that the hot side be used.


For NHRA compliance, use heavy-duty 1-gauge or 2-gauge welding cable for battery disconnect switches, especially with trunk-mounted batteries. The switch must be on the positive side, interrupting all electrical power, with the alternator wired to ensure the engine stops immediately when the switch is engaged

For Bonneville Land Speed Racing (SCTA rules), the battery disconnect switch must be installed on the positive side of the electrical system and act as a master cut-off for all electrical functions, including the alternator and ignition.

Re: battery disconnect switch
 

I don't really understand what you are saying in your first paragraph.

I do agree with the third and fourth paragraphs.

Re: battery disconnect switch
 

If you disconnect the ground first the hot post of the battery can lead to a spark if mistakenly touched to ground such as loosening the bolt on the cable end and momentarily touching the wrench to ground. Up to you which order you choose to use.