Battery Relocation to Trunk, NHRA approved method - Forums at Modded Mustangs
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post #1 of 35 Old December 28th, 2012, 05:55 PM Thread Starter
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Battery Relocation to Trunk, NHRA approved method

So ive been reading around about relocating the battery to the trunk and at first i thought it was a bad idea, re-wiring in general because i need my car to start every day no matter what and electrical issues from a battery relocation would not be good, until i found this. My Battery Relocation Project (MANY PICS!) - SVTPerformance



In most guides i have read, they tell you to ground everything out under the hood which i can understand, but then they tell you to run a hot positive 0 gauge wire using eyelets and a bolt and nut and run that positive wire all the way to the trunk... but this wire will be hot at all times so if there is any short it may cause a fire. so this correct method which is track approved uses a second starter solenoid and relay in the trunk, so that positive wire that is run from the front of the car to the back will not be hot at all times.


***The yellow & white wires I ran above were for the starter circuit. This is where I diverged from the referenced diagram. I extended the existing starter solenoid circuit back to the relay to operate my own solenoid instead of tapping off the ignition. The OEM starter solenoid circuit is bundled with the OEM starter cable, so I just reused that section (to get to the starter) and spliced on my wires...you can find the OEM starter solenoid circuit at the power distribution box under the hood (white with red stripe wire). The yellow wire brings the "starter engage" signal back to the relay and the white wire takes it back to the OEM wire that leads to the starter.

Should I do it?

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post #2 of 35 Old December 28th, 2012, 06:05 PM Thread Starter
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And heres where this guy got his ideas:http://www.modularfords.com/f17/relo...y-trunk-28052/

but it makes me nervous cutting my existing wire from my fuse box to battery, and the battery to starter wire under the hood... what if my car dont start when i re-wire all this mumbo jumbo?

Most sanctioning bodies require that the battery be placed in a box. Prepare accordingly and make sure you use the same 3/8" threaded ROD to bolt the box AND the battery through the floor (that is required by NHRA anyway). Use a large thick washer under the floor to prevent the battery from pulling through the floor in an accident. Rods with a J hook at the end are not usually accepted at the track. By the way, I do crash testing for the Big Three and I'm telling you that a 30lbs battery can do some serious damage if it comes loose in a crash.

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post #3 of 35 Old December 28th, 2012, 08:42 PM
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The big three have made you over engineer your trunk mount. What's wrong with a positive that's always hot? It's always hot under the hood and has the same risk of fire damage under the hood that it would have in the trunk. If you've already wired it that way it's fine, if you haven't wired it that way it's over kill.


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post #4 of 35 Old December 28th, 2012, 08:50 PM
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I think hes worried because that positive wire travels throughout the entire car usually under the carpet. I personally dont see a problem with it. Just be careful and dont throw daggers into your floor and you would be fine. Lol

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post #5 of 35 Old December 28th, 2012, 09:01 PM
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I think hes worried because that positive wire travels throughout the entire car usually under the carpet. I personally dont see a problem with it. Just be careful and dont throw daggers into your floor and you would be fine. Lol
+1 ...lol
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post #6 of 35 Old December 30th, 2012, 01:00 PM Thread Starter
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Its not that im worried, i just dont think that its safe, and if you were to take your car to a track that actually inspects, they wont let you run, unless its you use the diagram or something similar.

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post #7 of 35 Old December 30th, 2012, 01:30 PM
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I run 200A fuses on both of my hot lines

Go for it!











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post #8 of 35 Old December 30th, 2012, 01:47 PM
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Its not that im worried, i just dont think that its safe, and if you were to take your car to a track that actually inspects, they wont let you run, unless its you use the diagram or something similar.
I do go to tracks that inspect. Read the NHRA rulebook about rear mount batteries. Yours is overkill yet still missing the required cut off switch. If you leave your battery in the trunk with no cut off switch you will not be allowed to run as per NHRA rules. NHRA doesn't require all the extras you've added, they require that it's secured properly, separated by a firewall and protected with a cut off switch.





The following is not from the NHRA rulebook but covers it pretty well:


Power Shut-off Switches For Rear Mounted Batteries

NHRA rules specify that a 12 volt power shutoff (master disconnector) switch be installed if the battery is relocated to the rear of the vehicle. The switch is to be located in the positive wire close to the battery and easily accessible from the outside rear of the vehicle. This rule is intended to allow drag strip safety personnel to immediately shut down a vehicle in case of an accident. The NHRA rules state that the switch shall stop all electrical functions in the vehicle. A literal interpretation of the rule means the engine should immediately stop running when the switch is opened and some tracks enforce that requirement. Unfortunately, the engine on any vehicle equipped with a standard operation GM Delco alternator will not stop when the battery is disconnected. Once energized, the alternator will provide more than enough power to operate the ignition system and keep the engine running without a battery, even at a slow idle. (Have you tried yours?)

A master disconnect switch that has two sets of contacts (Double Pole -- Single Throw) can be used to meet the requirements on all GM vehicles utilizing alternators with external field wiring. The battery positive cable is connected across the set of high current contacts on the dual switch, and the "field" wiring for the alternator is opened and switched through the second set of contacts. Actuation of this switch removes power from both the battery and the field winding of the alternator causing the alternator to stop charging, and the engine will immediately stop.

To install the two pole master disconnect switch, perform the following steps, and then follow steps appropriate for the type of alternator you have:

1. Install the switch on the outside rear of your vehicle.

Fabricate a short section of battery cable and disconnect between the positive battery terminal and one large stud of the switch.

Connect the battery cable (running to the front of the vehicle) to the second large stud. Use brass crimp type connectors for the battery cable and crimp them with a hammer and small drift or punch. Carefully insulate both terminate with shrink sleeving.

2. Alternators with internal regulators:

Internal regulator units have the Field (F) terminal permanently connected to 12V. On these vehicles, cut the field wire (normally dark blue) between the alternator terminal (marked F and/or 2) and where the wire disappears into the wiring loom on top of the engine. Connect a new 14 gauge wire to the wire from the alternator field terminal, and route it to the rear to the new master disconnect switch. Connect the new extended field wire to one of the small studs using a ring connector either crimped on or soldered to the wire. Carefully insulate the cut end of the original field wire on top of the engine and tuck it into the wire loom.

Fabricate a short jumper using the same type wire and connect it between the second small stud and the large stud that is connected to the battery cable noted in step 1.B. (cable running to the front).


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Last edited by bulloch27; December 30th, 2012 at 04:12 PM.
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post #9 of 35 Old December 30th, 2012, 01:47 PM
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Im leaving mine up front and counter balancing it with a 5 gallon intetcooler tank in the trunk

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post #10 of 35 Old December 30th, 2012, 01:48 PM Thread Starter
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dude that thing is sexy. what if someone walked up to your car at a stop light and flipped that switch to off while your just sitting there....?

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post #11 of 35 Old December 30th, 2012, 07:38 PM
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dude that thing is sexy. what if someone walked up to your car at a stop light and flipped that switch to off while your just sitting there....?
then you'd loose that launch lol

Just flip the switch back and good to go




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post #12 of 35 Old December 30th, 2012, 07:43 PM
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post #13 of 35 Old December 30th, 2012, 09:32 PM
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I run 200A fuses on both of my hot lines

Go for it!








X2 my track inspects my car everytime and i have no issues, my car also starts everytime no issues
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post #14 of 35 Old December 30th, 2012, 11:23 PM
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Very much overkill! Here's a simple but effective way that passes NHRA.


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post #15 of 35 Old December 31st, 2012, 06:36 PM
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I ran my hot wire under the car (instead of under the carpet).

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post #16 of 35 Old December 31st, 2012, 08:05 PM
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I did too^ A thread can never have too many helpful pics so here are a few






I welded the 2 studs to the floor pan and then welded 4 bolts to the floor pan and bolted the box to the bolts. 4 bolts hold the box in place and then the 2 studs welded to the car hold the battery in place.




Poor mans way to crimp/solder wires without a terminal press or cable cutters
















Cut cable
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Beat the terminal down onto the cable with a hammer
Get a flat head screwdriver and use it as a punch to create a depression/crease down the center of the terminal parrellel to the cable to start to roll the center in
Turn the flathead perpendicular to the cable and use it as a punch to further smash down the terminal
Release the vice grips
Solder
Wrap up with electrical tape if you want


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post #17 of 35 Old December 31st, 2012, 10:28 PM
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Mines set up just like Jays but I also ran my wire under the carpet. Less chance of road debris coming up and slicing the insulation on the wire

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post #18 of 35 Old December 31st, 2012, 11:04 PM
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Mines set up just like Jays but I also ran my wire under the carpet. Less chance of road debris coming up and slicing the insulation on the wire

Sent from my LG-AS680 using AutoGuide App
I ran mine under the carpet cause I'm to lazy to get under the car!


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post #19 of 35 Old January 1st, 2013, 03:05 AM
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Have to say I'm not a fan of this. The wiring is exposed to high speed debris form the tires.

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post #20 of 35 Old January 1st, 2013, 03:17 AM
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for those that have done this and mounted the box on the right (passenger) side of the trunk did you guys put one stud (left stud) through the frame rail and the other just through the floor sheet metal?


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