Pics on battery cutoff switch

[kempkan]

I just purchased my battery cutoff switch for my relocation and I can't figure out what would look nice on my car. I have a 73 dart swinger and the switch is a summit part # sum-830050. My other question is ihra rules on on the switch. Can I use it on the negative side or does it have to be the positive side? Thanks for the help and pics.

 

[67Dart273]

You need to read the NHRA rules, which I'm not up on. For some reason you can download them from Bremerton:

http://www.bremertonraceway.com/2011 NHRA Rulebook.pdf

http://www.bremertonraceway.com/BREMERTON RACEWAY RULES.pdf

from here

http://www.bremertonraceway.com/

I wish you had asked before buying, it's a LOT easier to configure them using a 2 pole (4 terminal) switch, like this:

http://www.softcom.net/users/acnss/image/MasterDisconnectDPST1.jpg

You MUST have the switch (the large studs) in the POSITIVE cable. But you must configure it so that it not ONLY kills the battery, but ALSO kills the engine. The engine will continue to run on the alternator, whether it's a conventional (external regulator) or a "one wire" setup So you must devise a way to kill the alternator and so kill the engine.

There are also special provisions in the rules as to mounting the battery. If you don't have a metal firewall behind the seat, the battery must be in a sealed box VENTED TO THE OUTSIDE of the car. I don't remember, it might be that the box must be metal.

"crackedback" is probably the expert on trunk mount batteries around here.

 

[Vitamin c]

ive been working on this for the last week. I used an old tail lamp housing for mock up and when everyting fits ill move it over to a usable housing. Yes the switch needs to kill the motor and all power wired to the positive side. You do not need a steel firewall if you use a sealed and externally vented battery box. Jegs and Moroso sells the vented plastic box that will pass tech. There are several different methods to wiring your switch. you will need to study them and pick the one that suits your build. I use an alternator cut off solenoid mounted next to the alternator and wired back to my four pole switch.

 

[Purple Haze]

ive been working on this for the last week. I used an old tail lamp housing for mock up and when everyting fits ill move it over to a usable housing. Yes the switch needs to kill the motor and all power wired to the positive side. You do not need a steel firewall if you use a sealed and externally vented battery box. Jegs and Moroso sells the vented plastic box that will pass tech. There are several different methods to wiring your switch. you will need to study them and pick the one that suits your build. I use an alternator cut off solenoid mounted next to the alternator and wired back to my four pole switch.

Can you please post pic's and a wiring diagram of you setup? I have the battery cable part but need a diagram for the alt.part.

 

[67Dart273]

I don't know why you guys make it so darn hard. If you'd buy the 4 terminal (2 pole) switches, it's much easier

You have to run a BIG (say no6) charging line back to the battery, as posted here:

The problem with THIS diagram, is that there is some comments in the rules about "killing all power" and this leaves the alternator charging line hot at all times.

But it would be simple to fix: Get a "continuous duty solenoid," and mount near the battery with the contacts "inline" with the alternator chargning line. Ground one of the solenoid coil connections, run a no 14 back up front and tie it to "switched igniton". This will kill the charging line, and everything from front to back will be "dead" with the switch off.

 

[inkjunkie]

I have been told by a few people that pretty much no matter how you wire it you "might" get a voltage spike which if you have any elecrtonic devices in the car very well might fry them.....

 

[Purple Haze]

So what about a 4 terminal switch. The switch I have says 20 amp max.

 

[67Dart273]

So what about a 4 terminal switch. The switch I have says 20 amp max.

20A Nowhere NEARLY large enough.

But the 4 terminal (correctly called DPST, or "Double Pole Single Throw") have two large studs to put in the main battery circuit, and two smaller ones. The two smaller ones are normally NOT rated to pull full alternator current, which means if you have a "one wire" you need to use the small terminals to operate a relay or solenoid (continuous duty) which will break the battery AND alternator feed to the ignition, OR use the solenoid to break the charging line

Breaking the charging line MAY indeed generate a spike, but the worst it will kill will be the regulator in the alternator. I look at this as a small expense if it saves your life and keeps the car from burning.

 

[crackedback]

Here's something to think about. The main cut off switches are usually OK, BUT, do you want all the amp pull the starter draws running through the contacts?

I know I've posted these schematics before. Any of them are "legal" for NHRA/IHRA, however, some are better than others from a safety standpoint.

The last two are the same type of deal with your alt. The S on the solenoid is designates the S605 like in the pic above it. These are set up for a race car that you turn the master off after every run, the s605 will be active at all times when the master switch is in the "on" position. If you decide to use an S605 in your alt line on a street car, switch it off a hot line when in the RUN position. This way it's not putting a constant draw on the battery which may result in a dead battery after a while.

On my cars, I run the bottom schematic, you throw that master and there is NOTHING hot on the car outside a 2 foot cube in the trunk. Does it cost a bit more to run the ford/jeep solenoid and an S605, yes. I'll take that cost over potentially burning my car to the ground with a hot starter cable or Alt line running to the front. My friend burned a challenger to the ground from an always hot alt line... Not for me thank you!

 

[Purple Haze]

Wondering if you can just use the switch to kill the ignition and battery and not mess with the alternator at all. Seems to me it does the same thing as turning off the key and disconnecting the battery, everything is dead. Your drawings all show one wire alternators what about our alternators.

 

[crackedback]

If you are concerned about back feeding through the sense wire set up, you could put a diode inline.