Help with relay wiring!

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Dykes&Strippers
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Re: Help with relay wiring!

#16 Post by Dykes&Strippers » Tue Apr 28, 2009 10:39 pm

supernova wrote:
Dykes&Strippers wrote:Looking at everyones drawings, minus John's, I see some potential failure points that are not necessary. Everyone seems to want to put a solenoid in line of the MSD ignitions with their ign switch controlling this...Generally, we starting using these as a remote solenoid for the starter, and a greta place to tap for MSD power etc. The way the diagrams posted here are, they are not used for the starter but simply a power point for the rest of the car. That solenoid is a potential mechanical failure point. The simplest and cleanest way would be to use a through the fire wall connector...run your cable from the battery through the kill switch to that connector. From that connector you can now jump down to the starter. On the inside, you have a clean place to grab switch panel power as well as MSD power or anythig requiring battery power. This does several things..reduces the amount of wire, reduces a potential failed part, ensures you have propper current carrying capability to all accessories (at leaste 2 Ga), and gives you power both inside and out of the drivers/engine compartment.

Another point to add...in all cases where weight is not a factor, I also put a second through the firewall connector in and use this as a dedicated grounding point...also using at leaste a 2ga cable directly from the battery...eliminating the inconsistencies of grounding through the chassis.

I hope this does not offend anyone or stir up any arguments...just sharing some info and results we have picked up along the way. Hope to be of some help! :thumb:

You mean like this?
Yes!!!
Dykes & Strippers Custom Wiring
Lebanon, OH
513-617-5717

Harry Clack Dragster, 388" sbc, 4.80 @ 141

1978 Monza, 406 sbc, 5.59 @ 125

bracketracer
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Re: Help with relay wiring!

#17 Post by bracketracer » Wed Apr 29, 2009 6:23 am

Dykes&Strippers wrote:
bracketracer wrote:I have not seen a cut off switch that will handle a load from an alt...Maybe some one can post one??? I used a sol from here....Works great and the tech guys like it..
Cole Hersee part number 75912... go to colehersee.com. The best thing is to call their customer service center, give them your zip code and they will tell you who in your area sells their products!!! Thisis a true cut off switch...not a solenoid...rated for 175 amps continuous and 750 for 15sec.

Let me clear this upa little better :scratch: ..I was talking about the emergency cut off switch on the back of our cars. They have them now to hook up the the alt to it but think it's only rated at 20 amps... :scratch:

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Re: Help with relay wiring!

#18 Post by John_Heard » Wed Apr 29, 2009 6:42 am

I don't see what the problem is wiring the alternator directly to the battery outside of the main kill switch. If you're concerned about it in event of a wreck, put a high amperage fuse or circuit breaker in line with it.

bracketracer
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Re: Help with relay wiring!

#19 Post by bracketracer » Wed Apr 29, 2009 6:45 am

John_Heard wrote:I don't see what the problem is wiring the alternator directly to the battery outside of the main kill switch. If you're concerned about it in event of a wreck, put a high amperage fuse or circuit breaker in line with it.


John, it's in the nhra rule book..

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Re: Help with relay wiring!

#20 Post by John_Heard » Wed Apr 29, 2009 7:18 am

"..must break the positive side battery supply.." is what it says. The battery doesn't supply the alternator! Yeah, I know how that is interpreted but remember what the function of that switch is - to kill the car, fuel supply and other devices in event of a wreck/fire for driver safety. There is no danger that I can envision by hooking the alternator (only) direct to the battery, especially if equipped with an in line circuit breaker or fuse.

I've never been through a NHRA national event tech myself, but on the stuff we run around here nobody in all the years I've ran my car has even TESTED my shut off switch, let alone look at how it was wired. Mine works, it kills the car and it shuts all the fuel etc down like it's supposed to. I even go a step further and I put a secondary kill switch by the drivers seat so I can shut the car down from inside the car with one switch - why? Because you can not count on other people doing that for you in the event of a wreck or fire, period.

Bottom line NHRA/IHRA ought to address the issue of how to wire the alternator and what is ok and isn't, but they haven't. It's up to the individual tech inspector to decide that. And you know what 99.9999% are going to do? They are going to have you start the car up, then they'll slap that switch and see if it kills the car, fuel pumps, etc.

You make your own decisions on how you want to wire up the alternator - just make sure the kill switch functions as intended.

Dykes&Strippers
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Re: Help with relay wiring!

#21 Post by Dykes&Strippers » Wed Apr 29, 2009 11:14 am

bracketracer wrote:
Dykes&Strippers wrote:
bracketracer wrote:I have not seen a cut off switch that will handle a load from an alt...Maybe some one can post one??? I used a sol from here....Works great and the tech guys like it..
Cole Hersee part number 75912... go to colehersee.com. The best thing is to call their customer service center, give them your zip code and they will tell you who in your area sells their products!!! Thisis a true cut off switch...not a solenoid...rated for 175 amps continuous and 750 for 15sec.

Let me clear this upa little better :scratch: ..I was talking about the emergency cut off switch on the back of our cars. They have them now to hook up the the alt to it but think it's only rated at 20 amps... :scratch:
Correct...but incorrect! The Moroso switches are only rated for 20 amps on the alternator side. They have 2 3/8 post and two 10/32 posts. The part number I supplied gives you 4 3/8 posts that are rated for 175 amps continuous and 750 amps for 15 seconds.
Dykes & Strippers Custom Wiring
Lebanon, OH
513-617-5717

Harry Clack Dragster, 388" sbc, 4.80 @ 141

1978 Monza, 406 sbc, 5.59 @ 125

Dykes&Strippers
Posts: 12
Joined: Fri Feb 06, 2009 10:01 am
Location: Lebanon, OH

Re: Help with relay wiring!

#22 Post by Dykes&Strippers » Wed Apr 29, 2009 11:23 am

John_Heard wrote:I don't see what the problem is wiring the alternator directly to the battery outside of the main kill switch. If you're concerned about it in event of a wreck, put a high amperage fuse or circuit breaker in line with it.
I agree John...this discussion has came up a lot on other boards...with a lot of different concerns. With the alternator's wired directly to the battery, there is no way to completely isolate the battery from the car. Some racers are also experiencing a drain on the batteries during the week between races...again, the switch would isolate the problem. In the event of an accident, or even a shorted alternator cable....a fuse is the true answer in protecting our investments.
Dykes & Strippers Custom Wiring
Lebanon, OH
513-617-5717

Harry Clack Dragster, 388" sbc, 4.80 @ 141

1978 Monza, 406 sbc, 5.59 @ 125

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Re: Help with relay wiring!

#23 Post by John_Heard » Wed Apr 29, 2009 11:33 am

Something I used to use for the alternator at one time, back when I had one, was a forklift circuit breaker. It has a little button you can push it to disconnect the circuit. Works real nice for weekly storage, etc. high current also

Looks like this

Image

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supernova
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Re: Help with relay wiring!

#24 Post by supernova » Wed Apr 29, 2009 12:26 pm

Hey thanks for all the reply's and info. It has become an interesting thread.

I have a cole hersee p/n 24812 that was recomened for my application by Texas ind. ele. I talked to Steve there and he said that the relay I now have is the same one that Jerry Haas and Jerry Bickel order all the time from them. If it's good enough for those two guy's it's good enough for my.

This relay will be used as a switch and here are the specs.

12 Volt Continuous Duty
Special Applications: USED AS BATTERY
DISCONNECT SWITCH AND FOR EXTRA HEAVY DUTY ELECTRICAL LOADS.
USED IN MANY EMERGENCY VEHICLES APPLICATIONS LIKE,AMBULANCES,FIRE TRUCKS .
Amps: 225
Coil Type: Isolated
Coil Volts DC: 12 DC
Contact Form: SPNO
Contact Material: Copper
Duty Cycle: Continuous 225 amps; 1000 amps spike


I have a Flamming River push/pull 300 amp continuous use, 1000 amp spike switch for the back of the car. I also have a switch that will be next to the drivers seat. I hope to be able to shut the car down with eather switch and kill (fuel pumps, ignition, ect. ect.). What I came up with was the relay or (switch relay) to aid in that function.

I watched Kenny Esners King of the hill ( KOTH ) car burn to the ground last year because the switch at the back of the car was not shut off quickly enough. There is a video on it. Flames 25 ft in the air.
Now I don't have a 738 ci motor and 3 stages of nitrous with 3 fuel pumps but I do want to save my car from Kenny's kind of loss.

Here's the link to to the video. Notice that on one shuts off the power in the video.

http://videos.streetfire.net/video/Esne ... 163390.htm

So my thinking is, as long as both switches will kill all I will be happy.
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