Ford Mustang Forums banner

Moving the battery to the back

2K views 31 replies 15 participants last post by  89LXNotch 
#1 ·
I bought the Taylor relocating kit from Summit, and I think it's got most everything I need. Can I just run the + cable to the ignition coil and the - to ground and leave the rest of the wiring as is? The wires it came with are 2 gauge, is that big enough? Anything else?
 
#2 · (Edited)
2 gauge wire is fine. Run the + (pos) battery terminal to the same place it was before, on the solenoid next to the coil. Run the - (neg) terminal on the battery to ground (frame). Then run a 10 gauge wire from the - (neg) battery terminal to the front of the car to the computer ECU ground on the driver side fender apron. Make sure you have a good ground strap or cable from the block to the chassis. Factory ground strap is on driver side back of cylinder head to the firewall.

More info from Pro-M web site:

http://www.pro-flow.com/tech info/general tech.html

"Battery Ground problems

1. Don’t overlook the obvious. Grounding of the electrical system is extremely important. A few of our customers have had problems with the car running lean and very erratic. After hours of beating my head against the wall, Dave told me that his car started acting this way after he " smoked his 1000 watt amp and kickers". Armed with this information we checked the ground wire on the battery and found the small black wire running from the negative terminal on the battery to the frame near the washer bottle was destroyed by a short circuit.

2. Replacement of the wire made the car run like new and no further problems were present.

The same problem happens when you relocate the battery in the trunk. Most people chop the wire from the negative terminal to the frame and ground the battery using a short " Joe’s Discount Autoparts " cable to the frame rail in the trunk. Don’t do it!

DO IT RIGHT

Use a welding cable to connect the negative terminal to the engine in the same place it was connected before the move.

Use a second wire from the battery negative to the frame connector (near the washer bottle) use at least a #10 wire."

Pro-M Battery Relocation Diagram:
http://www.pro-flow.com/tech info/battery.htm
 
#3 ·
If your going to be NHRA legal, you have a few more things to do.

First is some cutting and splicing to wire the alternator correctly. Ideally, this is a great time to ditch that 2G POS, and upgrade to a real alternator.

But, in order for the cutoff switch to function, when its placed in the positive wire feed, you need to supply a continuous 12 volt current to the two black and orange wires.... and isolate that feed from the rest of the engine/electrical system.

That means cutting the wires that run to the alternator, splicing a 4 gauge cable to the two black and orange wires (large square plug) and running that cable all the way to the rear of the car, to connect to the HOT side of the switch.

Relocated battery, no switch, means NO race......
 
#4 ·
Yep, Kim makes a good point. It is something that almost everyone I see relocating their battery overlooks.

If you don't have the alternator isolated from the rest of the electrical system (eg. ignition system) the car will keep running when the cuttoff switch is thrown.

Do your homework. Make sure your wiring is correct and secure. Make sure your electrical system is safe. You do not want to kill power to the alternator while the car is running. You can damage your electrical system along with the computer, and end up chasing gremlins for a long time after.

If you simply band-aid your system together, you are going to have problems. Also, if your track does a decent job of teching, you will not pass.

Paul
 
#5 ·
I just got nailed in tech for this same thing. I knew I needed a batt cut off switch but I didn't want to cut a hole in the back of my car. My question is, doesnt the cutt-off switch just have to break the positive side of the batt cable? I didn't know it had to break the power to the ignition and everything else... anyone know where to find a diagram on how this must be wired?

Didn't mean to hijack but its something we all need to know I guess...
 
#6 ·
I just told you.

Cut off switch has to kill the car, that means fuel pumps, ignition, etc.....

The cut off has to be in the HOT wire or positive side of the car.

You have to move the location of the HOT side of the alternator pickup to the battery side of the switch.

What bumper are you running?

You can mount the switch under car, use an extended pushrod (Removeable) to activate the switch. It has to be mounted in a PUSH-OFF fashion. Nothing else has to be changed.

Of course everytime the car is tech'd, your deck is going to lose its pre-sets.

If ya want I can shoot a picture of where my switch is mounted. Its an ancient car, and the bumper cover isn't nearly as long as the SN95's. But Your only talking about a 1/4" diameter hole in the bumper cover. When you remove the push-rod, simply pop in paint matched body clip (one of those plastic buttons) and from 3 feet no-one will know its there.

Also, if your good, and quick, the battery cut off makes a great anti theft device. Simply throw the cutoff, and unless someone saw you do it, OR they tow the car.... they can futs with the thing all day long and it aint going no-where.
 
#7 ·
Here's a pic of my cuttoff switch mounted inside the battery box along with the solenoid. It's a tight fit. Probably won't happen in any other box except for the newer summit box which is one piece and a little bigger. Best box I have ever seen and installed (in brothers car).
You'll have to do some measuring and alignment to get the rod correctly positioned, but it's worth it. Pull the rod out when done racing and no one can tamper with your switch.



 
#8 ·
Thanks a lot Paul for the pic, thats all I needed to see.

Kim, thanks for the idea with the body clip too, my car is black so that will be an easy one to hide...

I dont know why I was thinking that I had to cut a huge hole in my bumper to mount the switch, I guess I was just used to seeing the monster switches that some guys at the track have rigged up. I really like that rod behind the tag, bad thing is with my SN95 most of my trunk lifts up including the tag so I almost have to use the rear bumper.
 
#9 ·
good tips. i have been wanting to relocate my battery for awhile, thanks alot..... really, good pic also...., don't know what i would do with out corral??????.................., lol
 
#10 ·
I got the Flaming River cutoff switch with the rod (same as the pic I think). Does the rod have to be directly in line with the switch, or can it be at a small angle? I'm asking b/c I still carry around my spare tire and there isn't a lot of room to mount the box.

I am planning to use 2 gauge wire for the + and - sides, will that be OK? What do I use to crimp connectors on wire that size?

Thanks!
 
#11 ·
The rod can be at a little bit of an angle. It uses a ball joint socket type connector so it will pivot any direction to a certain extent.

2 gauge should be big enough. I've heard others use it and it works. It really depends on how much electrical load you have. Big stereo, electric fan, fog lights, blah blah. I recommend 1/0 because that's what I was told by a pro, plus I have a bit of electrical experience and knowhow. My car is over-wired, but I wouldn't have it any other way. I have room to grow and it cranks easier than it did when it was stock. There's a lot you can do to improve the electrical system on fox cars. I just got done hiding the wires. I completely re-wired all of the wires leading from the computer to all the various sensors. I shortened, moved, and improved the grounding system as well as some power wires. Next up will be the headlights wired to relays. It just keeps getting better and better.

Do your homework, do it right and you'll never look back.

Paul
 
#12 ·
I do have a decent stereo in the car, but I rarely use all of it. When I head to the track, I just leave the sub at home so I've just got one amp running the regular speakers. I am planning to completely remove the 2nd amp and sub in a few months since this is become more and more of a drag car all the time, but I do still drive it to the track.

I don't have any foglights, but I'll probably get an electric fan in a month or two. I have my A/C and heater removed (except for the stuff under the dash), so they aren't an issue. The only other stuff I can think of that may be an extra draw on the electrical system are gauges, MSD 6AL, and Blaster 3 coil.

Other questions, how many ground wires do I need? I'm planning to go from the - terminal to the quad shock mount on the frame. Where else do I need to put one?

Will I need fuses in either of the wires from the switch (to the coil or alternator)? If so, what size?

Thanks!
 
#13 ·
You should be wiring the alternator directly to the hot side of the cuttoff switch. This is hot at all time. You can fuse this wire. I'd use a fusible link. You need one 2 sizes smaller than the wire you use. If you use an 8 gauge wire to run from the alternator to the battery, use a 12 gauge fusible link. The cuttoff switch (switch side) then should feed the rest of the car. If you use a fuse, I'd use maybe a 50 or 100 amp fuse from a stereo shop. Not some cheapie. Depends what you have running. How much current it will draw.

As far as grounding, I grouned mine to the thin metal of the spare tire well. It turned out to be a great ground with my 1/0 cable. I also run a ground from the frame near the front sway bar mount to the engine, and also the engine strap to firewall. Works very well.

Paul


PS always run as big a ground as your + wires, it's all the same current path.
 
#14 ·
One thing that hasn't been mentioned that may be a bug you run into:
If you are still running a stock starter and running longtubes the heat soak of the starter combined with the slightly weakened power signal from the relocated battery may result in hot starting problems.
I don't know if the 92 motors had the smaller starters on them or not, I think the one I'm using came off a 94 GT. Its a smaller diameter, like 3-4" as opposed to the factory unit thats more like 5-6" in diameter. The smaller one has an external solenoid. It provides a lot more clearance from the headers and I haven't had a hot starting problem since I installed it.
Before that, when I moved the battery, if I try to crank it after its at full operating temerature, it would kind of turn over once, then click a few times and sometimes I would have to wait a while to turn it over. This can be a major problem if you are having to hot lap the car in elimination rounds, etc... and you are not able to open the hood to let it cool off faster.
 
#16 ·
Good point, although I have never had a starter problem with my long tubes and original 89 starter. Like I said, it actually cranks nicer now than when the car was stock. This of course is attributed to the large gauge wire I use. If you keep the solenoid in the front and run power cable to that, then to the starter, you have at least 15 feet of cable. This in my opinion needs larger than 2 gauge to be effective.
My solenoid is in the battery box in the rear so I have about a 10 foot run. 10 ft, 1/0 cable, good connections, same size cable for grounding all equals no problems. If any exist, you can bet it's starter related.

I am able to hot lap my car, shut it off, start it up, several times with no loss.

I think long tubes and heat soak get a bad rap when there's too many people that have poor connections, old wire (with oxidized connections, freying connections, etc.) or too small of gauge wire for the task.

This being said, I know all headers and clearances are not the same. I'm sure some of them are very tight and do cause some serious heat problems. I think my settup is fairly typical though with original starter and BBK longtubes.

Paul
 
#19 ·
Unless you have a 400 amp alternator, I have no idea why you would run 2 gauge wire off of the alternator??????

I think 6 gauge would be enough for most any alternator.
I run 8 gauge off of my 130 amp 3G alt
 
#20 ·
8 gauge is too small for 130 amp delivery. As the length of wire run goes up, the gauge of wire has to come down to minimise resistance, and increase dleivery.

If the circuite were original, then 6 gauge would be acceptable.

Minimum wire for front to rear would be a 4 gauge, and 2 gauge is barely overkill. 2 gauge for the battery to starter is minimum acceptable, and 0 gauge is optimum.

As for the question above, "splice"? SImply run an eye on each end, and route the wire from the switch, to the back of the alternator.
 
#23 ·
I mounted the cutoff switch behind the license plate, and spaced the plate out with some standoffs I got from www.mcmaster.com
I also use 1/0 welding cable for the pos cable, and a 4 ga ground from the engine block directly to the battery. The only problem in relocating the batt to the trunk is the always hot main power cable. I'm going to relocate my starter solenoid to the trunk, run a fused 8 ga main power wire to a front mounted destribution block, and use the 1/0 cable to power the starter.
 
#24 ·
Kim, I guess in my case, the alternator either never delivers the full 130 amps, or if it does it is only for very short moments. The 8ga wire is relatively short down to the main lug on the starter (PMGR style)

My total current draw probably never exceeds maybe 80 amps or less for the whole vehicle.

My starting circuit consists of a 850 CCA group 34 size battery and exactly 12 feet of #4 welding cable (I thought I would have extra but it was just barely enough) running a PMGR '93 up style mini starter.

The Neg side of the battery connects directly to the rear frame with a #2 cable. The front of the frame has a 4 ga ground cable running to the alt bracket, and a 8 ga jumper from the frame to the cab (93 Ranger) and also to the main ground lug for the ECU. I also have a 8 ga jumper from the main ECU ground lug to the intake manifold.

I think one reason I have never had any starting problems is due to having the PMGR mini starter. I would like to see the cranking amps draw of it versus the larger old style Ford starter. My engine cranks at 450 RPM.
 
#25 ·
kim said:
8 gauge is too small for 130 amp delivery. As the length of wire run goes up, the gauge of wire has to come down to minimise resistance, and increase dleivery.

If the circuite were original, then 6 gauge would be acceptable.

Minimum wire for front to rear would be a 4 gauge, and 2 gauge is barely overkill. 2 gauge for the battery to starter is minimum acceptable, and 0 gauge is optimum.

As for the question above, "splice"? SImply run an eye on each end, and route the wire from the switch, to the back of the alternator.
All the wires I'm using for this are 2 gauge.

I've been using this page as a guide:

http://buffhomer.corral.net/custom.html

Is the information here correct? Reading the part about disconnecting the alternator from the charging system gives me the impression that I cut one wire from the alternator and go to the kill switch with 2 gauge. Is that right?
 
#26 ·
Yes, route the alternator to the always hot side of the kill switch.
 
This is an older thread, you may not receive a response, and could be reviving an old thread. Please consider creating a new thread.
Top