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I need to install an emergency battery kill switch on a 72 Camaro for the NHRA tech guys at our strip. Just installing a disconnect switch isn't going to kill the motor is it? I'm thinking I have to have a relay on the 10 gauge wire going to the alternator, to break that circuit, and keep it from self exciting, and therefore running, correct????


:sweat:

Thanks for your help!

MF
 

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Discussion Starter #3
Thanks Malc we already have the two post switch, so we will use a fordtype solenoid rated continuous duty to open the alt supply wire.

thanks for your fast response!!!

MF

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Doc here, :pimp:

How many Wire Disconnect switch do you have , 2 or 3 wire?

Doc :pimp:
 

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Discussion Starter #5
Hey Doc
It's a simple two post. Single pole, single throw. I hooked up a small relay to test my wiring theories last nite, and realized that I had overlooked the detail about bringing the feed for the alternator from upstream of the battery disconnect switch. I will change that with a piece of #8 wire and a Napa ST-95 relay tonight.
Thanks to you and Nalc for your help and diagrams!!

:thumbup: :thumbup: :thumbup:

MF
 

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Doc here, :pimp:

IF you plan on using the relay, How do you plan to Control the Coil?

AND If you wire it Full time to the Disconnect Switch, You , If the switch is NOT turned off After,Every Use, Will have a dead battery..(Relay Engaged 24/7/365)..

And if you wire past the disconnect to control the Relay, May not satisfy NHRA regs..

A better thought might be install the new Alternator wire and proper links for that Wire only..and wire it to the battery..When the E Stop is engaged The Alternator will be isolated from the Vehicle system..and I think (not sure) It is acceptable.

The only Gray Area might be that wire is Hot after E~Stop is engaged but not able to support the ignition..

Remember the relay will be on all the time if not controlled by an External switch and wired to the disconnect..If left on all the time Will flatten the battery.

Just a Thought..

Doc :pimp:
 

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kill switch

Dear Sir
Why don't you put an electrical fuel cutout in line with your tank and hook that up to your cutout switch?
dugthegreat
Mrfixmaster said:
I need to install an emergency battery kill switch on a 72 Camaro for the NHRA tech guys at our strip. Just installing a disconnect switch isn't going to kill the motor is it? I'm thinking I have to have a relay on the 10 gauge wire going to the alternator, to break that circuit, and keep it from self exciting, and therefore running, correct????


:sweat:

Thanks for your help!

MF
 

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Doc here, :pimp:

A fuel cutout or roll over switch is a nice addition , but It, by itself alone won't satisfy regs..

They want it to dead stop the engine ..with a Fuel cutout you must burn off excess fuel first..

Also the cut out removes another possible fire ignition source in case of accident, the high current electrical shorting to ground. A fire that can not be put out until the source is removed .. (the Battery) .

Doc :pimp:
 

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Hi Doc-
Sorry to resurrect the thread, but I had something kicking around in the old noggin for a month here.....

Your next to last post
"A better thought might be install the new Alternator wire and proper links for that Wire only..and wire it to the battery..When the E Stop is engaged The Alternator will be isolated from the Vehicle system..and I think (not sure) It is acceptable.

The only Gray Area might be that wire is Hot after E~Stop is engaged but not able to support the ignition..

Remember the relay will be on all the time if not controlled by an External switch and wired to the disconnect..If left on all the time Will flatten the battery."


It got me thinking. Why couldn't you use the power from the ignition switch to fire the coil of the relay as well as turn the ignition on? Try to follow my logic here:

E- Switch (2 pole) #2 ga cable In from battery #2 out to starter/power to everything else ie ignition, lights, fuel pump, everything.

Alternator: #8 wire to continuous duty relay to pos. terminal of battery
This relay would get its triggering power from the ignition switch.

If the E Switch is shut off, it kills the ignition switch power, which would also kill the power to the relay on the alternator. Thus opening the relay, killing the alternator. That would eliminate any "Run on" as well. And when you shut the car off with the ignition switch, the alternator line is dead as well.

Wouldn't it work, or am I missing someting?

By the way, thanks for all the input!!!!
 

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this has been jogging my mind for some time now..I read the other thread and was wondering this..in the old days..prehistory...we just ran a piece of battery cable to the kill switch and then all the wires were attached downstream from the kill switch..this had the same effect as pulling the cable off of the battery when the kill switch was engaged..(turned off)..that is the way we accepted it in the old days..

Now the kill switch is just for that event of an accident and is intended to kill all power to all the car systems..it is not used for starting and stopping the engine or anything else..

On a newer car there is a wire from the battery terminal that goes to a buss and that runs all the computers and other electrical stuff that we find..Doing it my way just invoves moving one wire from the battery terminal to the downstream side of the kill switch..

Let me know if this works for you..

Sam
 

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Doc here, :pimp:

JEFF,

Your Idea would work fine , If I understand it correctly, but has two drawbacks..
  • The relay would have to be a continuous duty relay (would not heat under long duration runs) The More expensive Marine or Forklift type relays would be needed..
  • The relay would have to be contact rated for , Like 150 amps continuous operation..To Safely support a 100 amp alternator. The relay would be big and Expensive...
I'll try and draw a "Total" Isolation system schematic for you tonight, and see if it is similar to what you want and try and post it In the AM..



SAM,

The only problem with that, Is on today's vehicles, Once the Alternator is charging, and the battery is removed from the system, Via the E~Stop, the Engine will continue to run supported by the alternator. BECAUSE the alternator and Ignition are on the same side of the E~Stop

So the dilemma we face is two fold, the Battery MUST be isolated from the Power support bus, (Ign, engine Bay...Ect..) AND the Alternator must be isolated from the from both the system at E~Stop..(which on a 2 pole E~Stop, puts the Alternator wire at the battery Side of E~Stop, and HOT at all times) AND (not sure on the NHRA on this one..there should be no active HOT wires beyond the E~Stop in case of accident, even a small relay wire) A Review of the Rules would be needed.


Doc :pimp:
 

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Hmmmmm,,,, more ponderings

For the sake of arguement, if it were wired the way I described, and put a fuse near the battery, would THAT suffice? If it shorts, the fuse blows....viole'!

Regarding the solenoid ....RV Solenoid?? It only has to be on for less than a few minutes, for the most part. And that is to warm up the car. I can't think of a time when the car runs for more than 5 minutes straight.
 

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Doc here, :pimp:

If the Car will only run 5 minutes max..at anytime, you can probably get away with a ford Type solenoid..no sweat..longer than that and you will have heat problems.

I drew several schematics using your parameters, but without a double pole single throw E~Stop, could not make anything work as a "Total" kill switch and maintain Isolation between the charging system and the ignition system without leaving AT LEAST one hot wire going forward..(and I don't think that will satisfy NHRA rules) The easy way is to get the Single throw double pole E~Stop and use that..

I don't think the fuse will be acceptable, you can't depend on it to short in case of a wreck..AND pulling the E~Stop won't stop the engine..(What is what they want to see..)

Now that I know we can use Ford type solenoids, Let me think on using TWO solenoids off the E~STOP... for a total kill system..just off the top of my head, I'm thinking that might work .

Doc :pimp:
 

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In all honesty, I think the Tech guys only care that the car shuts off with no "run on" when they slap the button. If the motor dies, then the alt can't charge. Even though the hot from the bat (before the switch) goes to the alt.
 

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Doc here, :pimp:

If that is the case this should work OK:



Doc :pimp:
 
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