Battery disconnect with rear mount battery?

[Rileys68Camaro]

What would be the best way to do this? I was planning on mounting an optima over the right rear tire and I've ran the + cable to the firewall, but haven't drilled the firewall yet or mounted the battery or - cable.



I'm using Quick Car cables, and a kit from Mark(can't remember the company name) wire upgrade kit and Painless 18 circuit harness.

I just found the kit, it's a MAD Enterprises kit.

[CarlC]

Do you want the switch accessible from the outside of the car or only in the trunk?

[Rileys68Camaro]

Inside for now. I'm trying to build my car for the street, with the option of some minor mods to be safer at a track day, but nothing serious.

If it was accessable from outside, I'd want it somewhere out of site and not sticking throught the body.

It's a tough balance.

[West Texas Z]

I know how you feel. I'm in the same situantion too. lol ^

[CarlC]

Did you see this?

https://www.pro-touring.com/forum/sh...ighlight=carlc

[West Texas Z]

Hey Carl, how did you make that bracket for the cut off switch? or is it baught? Looks great BTW.

[Rileys68Camaro]

I did, but I missed where you mounted the groung cable.

I love your cheap(really just inexpensive) ideas, I read about the welding cable after I bought the Quick Car stuff. Next time.

[CarlC]

It's just a piece of sheet aluminum, a few screws, and two clamps. About $3 worth of stuff.

I could not find anything that worked for me, so this is it. Not fancy, but effective.

[West Texas Z]

looks awesome. I wouldnt mind one for my aluminum battery box. I could find someone to weld it to the side or something. Wanna build me one? I'll pay you for your time and materials.

[Steve1968LS2]

Here's how I did it on my Fairlane.

http://www.popularhotrodding.com/tec...ion/index.html

Just don't use the long rod for the switch, you can add it later if you ever have to pass NHRA tech. The gizmo from AAW works great by the way.

[CarlC]

I appreciate the offer but time is short for me now. I don't have enough time to work on my own new projects.

[MonzaRacer]

Just put the cutoff switch in the ground wire when you hook the negative cable to the chassis.
Did it in my Monza and it worked perfect.

[oldcarguy]

Just remember if your doing this in a subframe car, if you ground to the rear subframe, to ground front & rear together, or you won't get a good ground for engine parts !

[West Texas Z]

Just remember if your doing this in a subframe car, if you ground to the rear subframe, to ground front & rear together, or you won't get a good ground for engine parts !

So... I should be fine with a stock chasis frame right?

[David Pozzi]

Another way is to mount a late 80's Ford solenoid in the trunk, run the positive cable through it and on to the starter. Make a small jumper wire on the starter from cable to starter switch terminal, so when the cable is hot, the starter runs.

Run the start wire that originally went to the starter back to the solenoid in the trunk. Now the starter will run when you turn the key but the large cable will only be hot when the key is on start.

Run a 10 gage hot wire from horn relay power terminal (on a Camaro) back to the battery switch, this will power all your systems. You can put a switch in this wire to disable the car's electrics when parked. If you want the radio memory to stay intact, run a 14 gage wire from battery side of this switch to the radio memory/clock wire.

The switch in the trunk can now be a small 50 amp toggle switch since it doesn't handle full starter loads. There are small HD switches for fog lights available and are inexpensive.

Benefits:
1 large starter cable isn't hot all the time, less chance for fire if it shorts out.
2. Shut off switch can be small, just a toggle.

Drawbacks:
If it were turned off with engine running, the alternator would probably keep the engine running. To make it shut off, the alternator activation wire would need to be run back to the switch and the switch would probably have to be changed to a double throw double pole type, so the alt wire can be on it's own circuit and not feed back to the ignition.

With the usual large power switch on a car, you will probably have the same alternator problem and the car won't shut off via the trunk switch.

Warning, disconnecting the battery from a running alternator can cause a voltage surge and damage electronics in the car, be careful testing any disconnect switch.
David

[MonzaRacer]

If the car has an alternator and looses ground it wont run, power needs a full circuit.
I had my previous Monza wired with a heavy cable (well shielded 2/0 welders cable) then ran it inside some heavy fuel line (it looked like a fuel line so got a friend to make me some battery positive labels from lable maker)1/2" I think. up to an Echlin starter solenoid froma 86 Ranger (the newer rounder Ford solenoids are more stable than the older Ford ones) on the pass. firewall between the engine and the heater/AC area. ran a heavy wire to my starter and just made a sheet metal jumper for the batt/s term connection but having a short piece of heavy sheet metal, drilled my 3/8 hole then slipped it over the stud and scratched the s terminal and drilled there and tada free jumper strap.
run another 2/0 cable to the solenoid and start wire to solenoid and it was much easier to bump engien too.
My battery was back in spare tire well of the Monza on the passenger rear.
I ran several of the braided stainless ground straps from the block to front "frame rails" my rear ground ran to an exsiting bolt hole in the rear "frame"
I never had seconds trouble this way and my Pianless switch was simply mounted in the rear panel next to the right tail light.
with no ground path to the battery the alt cant work.
If you dont like the heavy hot wire yes you can run a "trip " solenoid in back BUT if the solenoid fails your stuck.
Thought of this set up but went my way as its safe ,simple and it works perfectly.
Big trick is heavy cable, well made crimps(I bought my own crimper when I did a lot of stereo work.
I use welders cable as the finer stranded wire makes it easier to handle and manouver and can carry amperage with less resistance.
I will try to dig out all my old parts and show what I did.

[David Pozzi]

"with no ground path to the battery the alt cant work"

Yes it can, if the engine is running and you disconnect battery ground, the alternator is still grounded to the engine and keeps the engine running because the ign switch is still on. Just the battery is removed from the circuit. You need to break the alternator field circuit separately from the ignition circuit. When you look online for master disconnect switches, they list two pole for non-alternator cars, and four pole for cars with alternators.

David

[jeff5347]

i had the same problem. Have my batt in the trunk and run a Ford solenoid. i put a shut off switch in the License plate and ran all the wires needed. i had the same problem with the car still running after killing the switch. I forget but i can look but i had to wire it as you say so the alt would not keep the car running. It was a P.i.A. as i had to sit and figure out how the electrical was working. i got it after 3-4 hours. Just wanted to throw my 2 cents in as it will keep running if not wired correctly. Now i can start the car like normal, shut it off like normal, and kill the engine when i killthe shutoff switch. Works like a charm. Plus no one knows what it is so if someone ever tried to steal the car the switch is off.

[woody80z28]

I got the same kit from Mark at M.A.D. To be NHRA-legal I put my kill switch under the license plate. Not visibile on the street, but "easily accessible from the rear of the vehicle" for the track.

Texas Z, unless you have solid metal body mounts, your front subframe is insulted from the body & rear fame of the car.

[Skip Fix]

Since most are discussing disconnects to eventually go drag racing be sure your battery hold down meets specs, ie correct sized bolts and a sealed box if not a sealed battery or a completely sealed rear seat area. Most of the tech guys I've seen get on guys for those regularly. even if you figure most factory hold downs are pretty cheesy but since they are in the engine compartment they don't worry unless they are loose.