Battery Relocation Ground Opinion


Mustang Master
Mar 12, 2009
Mooresville, NC
So my car is currently under construction with bits and pieces scattered all over the garage (it never ends)! The battery has been relocated to the trunk and is grounded to the body with another ground running back up to where the engine will eventually be. The motor is out while I paint the engine bay and install the K-member. I need to roll down the windows to install new guide bushings and run channel weather stripping. Can I can power the car on with just the body ground? I'm not trying to start it or anything, just need to power it up to roll the windows up and down. I'm leaning towards yes, just wanted a second opinion.
  • Sponsors(?)


Well-Known Member
Sep 9, 2013
Southern CA
I have never done exactly what you are describing. However, as long as its a solid ground (I like to ground to the frame itself), based on my electronic/electrical experience, I don't see any issue with it. Even when the battery is in its normal location, its grounded to the car. You will read ground with a meter whether its in the trunk or whether its up front. I'm sure you know this, but I just like to be clear in my explanations, so whoever reads it can put it all together.

Maybe this helps. Good luck working on your car!


man bewbs please...
Mar 23, 2007
Pacific NW
When I installed the battery in the trunk of my car, ( mounted right rear) I ran the battery ground cable from the negative post thru the trunk floor and straight to the bolt that used to mount the quad shock to the frame. I did not run a cable forward to the engine. I ran a ground strap from the block to the frame, that is until I ran solid engine mounts, now there is no need to run the ground strap on the block anymore as it is directly grounded to the frame.


StangNet's favorite TOOL
SN Certified Technician
Mar 10, 2000
Dublin GA
Rear mounted battery ground wiring. Follow this plan and you will have zero
ground problems.

One 1 gauge or 1/0 gauge wire from battery negative post to a clean shiny spot
on the chassis near the battery. Use a 5/16” bolt and bolt it down to make the
rear ground. Use a 1 gauge or 1/0 gauge wire from the rear ground bolt to a clean
shiny spot on the block.

One 4 gauge wire from the block where you connected the battery ground wire to
the chassis ground where the battery was mounted up front. Use a 5/16” bolt
and bolt down the 4 gauge engine to chassis ground, make sure that it the metal
around the bolt is clean & shiny. This is the alternator power ground.

The computer has a dedicated power ground wire with a cylindrical quick connect
(about 2 ½”long by 1” diameter. It comes out of the wiring harness near the
ignition coil & starter solenoid (or relay). Be sure to bolt it to the chassis ground
in the same place as you bolted the alternator power ground. This is an
absolute don’t overlook it item for EFI cars

Note: The quick disconnect may have fallen victim to damage or removal by
a previous owner. However, it is still of utmost importance that the black/green
wires have a high quality ground..

Picture courtesy timewarped1972

Crimp or even better, solder the lugs on the all the wire. The local auto stereo
shop will have them if the auto parts store doesn't. Use some heat shrink tubing
to cover the lugs and make things look nice.

For a battery cut off switch, see
is the switch is the installation instructions.
Use the super duty switch and the following tech note to wire it and you will
be good to go.

Use the Moroso plan for the alternator wiring and you risk a fire. The 10 gauge wire they recommend is even less adequate that the stock Mustang wiring.

There is a solution, but it will require about 40' of 18 gauge green wire.

Wire the battery to the two 1/2" posts as shown in the diagram.

The alternator requires a different approach. On the small alternator plug there is a green wire. It is the sense lead that turns the regulator on when the ignition switch is in the run position. Cut the green wire and solder the 40' of green wire between the two pieces. Use some heat shrink to cover the splices. See for some excellent help on soldering & using heat shrink tubing.

Run the green wire back to the Moroso switch and cut off the excess wire. Try to run the green wire inside the car and protect it from getting cut or chaffed. Crimp a 18 gauge ring terminal (red is 18 gauge color code for the crimp on terminals) on each wire. Bolt one ring terminal to each of the 3/16" studs. Do not add the jumper between the 1/2" stud and the 3/16" stud as shown it the
Moroso diagram.

How it works:
The green wire is the ignition on sense feed to the regulator. It supplies a turn on signal to the regulator when the ignition switch is in the Run position. Turn the Moroso switch to off, and the sense voltage goes away, the voltage regulator shuts off and the alternator quits making power.

The fuse & wiring in the following diagram are for a 3G alternator. The stock alternator uses a dark green fuse link wire that connects to 2 black/orange wires. Always leave them connected to the starter solenoid even if you have a 3G alternator.

See the following website for some help from Tmoss (diagram designer) & Stang&2Birds (website host) for help on 88-95 wiring Everyone should bookmark this site.

Ignition switch wiring

Fuel, alternator, A/C and ignition wiring

Complete computer, actuator & sensor wiring diagram for 88-91 Mass Air Mustangs

Vacuum diagram 89-93 Mustangs


New Member
May 21, 2009
North Cackalacky
Thanks @jrichker. I was planning on running a ground wire from the body ground back up to the engine block, just didn't know if I could turn the ignition power on to roll down the windows without the engine ground in place yet.
Thread starter Similar threads Forum Replies Date
S Where does this negative cable go??? 2005 - 2009 Specific Tech 3
StreetDreamsGT Should the power and ground wire both be the same size for battery relocation? Fox 5.0 Mustang Tech 7
Fett Battery relocate ground question. Fox 5.0 Mustang Tech 4
B Those who relocated the battery, grounds? Fox 5.0 Mustang Tech 2
SilverStallion Where To Ground Relocated Battery In The Trunk? SN95 4.6L Mustang Tech 8
D Battery relocation subwoofer concern SN95 4.6L Mustang Tech 1
Anti_Hero0932 Battery Relocation Fail - HELP Fox 5.0 Mustang Tech 14
J Help! Battery Relocation Cable/fuse Size Issues?!?! Fox 5.0 Mustang Tech 19
A Electrical Battery Relocation Problems 1994 - 1995 Specific Tech 3
bird_dog0347 Battery Relocation Kits, Talk To Me Goose... 1979 - 1995 (Fox, SN95.0, & 2.3L) -General/Talk- 45
Knowbody Fox Battery Relocation 1979 - 1995 (Fox, SN95.0, & 2.3L) -General/Talk- 12
screamin gt Trunk Battery Relocation Thoughts SN95 4.6L Mustang Tech 8
pete_05_gt Upr Battery Relocation Help Fox 5.0 Mustang Tech 7
M Battery Relocation 1994 - 1995 Specific Tech 1
9 Wire Tuck And Battery Relocation The Welcome Wagon 4
B Electrical Need Help Relocating Battery On 94 Cobra Fox 5.0 Mustang Tech 2
R Battery Relocation 1965 - 1973 Classic Mustangs -General/Talk- 10
MustangMando Battery Relocation For Efi 1965 - 1973 Classic Mustangs -General/Talk- 4
sen2two Relocating My Battery.... Solenoid Just Clicking? Fox 5.0 Mustang Tech 14
billison New battery tray vs trunk relocation Fox 5.0 Mustang Tech 23
JymboSlice Anyone with a battery relocate? SN95 4.6L Mustang Tech 8
rio95 battery relocation question and opinions needed 1994 - 1995 Specific Tech 21
moonraker Battery relocation - what fuse? Classic Mustang Specific Tech 5
S Steeda battery relocation kit Drivetrain Parts 1
87WhiteStang1 just did battery relocate Fox 5.0 Mustang Tech 3
D Battery Relocation, what a pain 1979 - 1995 (Fox, SN95.0, & 2.3L) -General/Talk- 2
70vert 31" radiators thread - battery relocation mandatory. Classic Mustang Specific Tech 10
RickieFrat Mustang Battery Relocation Kit Interior Exterior Parts 0
RickieFrat Mustang Battery Relocation Kit Interior Exterior Parts 0
Rickyll7 battery relocation kit... 1996 - 2004 SN95 Mustang -General/Talk- 7
1 3G alternator, Mini Starter, and Battery Relocation Classic Mustang Specific Tech 8
Adam95GT Battery Relocation???? 1994 - 1995 Specific Tech 6
K Help relocating battery Fox 5.0 Mustang Tech 7
Sanctus Battery Relocation ? 2005 - 2009 Specific Tech 9
mhanksii NHRA Rules and Battery Relocation 2005 - 2009 Specific Tech 7
Brother Battery Relocation Regional Forums and Event Information 2
GTA_V6_Mustang Just got battery relocation kit... Anything I should know? 1994 - 1995 Specific Tech 1
98blackstallion battery reloc. kit, rear drag springs?? SN95 4.6L Mustang Tech 20
what9612 anyone with a battery relocation kit? 1996 - 2004 SN95 Mustang -General/Talk- 9
Guero Battery Relocation Fox 5.0 Mustang Tech 4
steedastangt battery relocation kit - need help SN95 4.6L Mustang Tech 2
Dean85GT Which battery relocation kit? 1979 - 1995 (Fox, SN95.0, & 2.3L) -General/Talk- 8
Ronald_McDonald Battery Relocation Troubles Fox 5.0 Mustang Tech 1
G relocating battery.... Fox 5.0 Mustang Tech 1
B Battery Relocated...starting issue... Fox 5.0 Mustang Tech 20
D 2 gauge cable for battery relocation Fox 5.0 Mustang Tech 6
Bosko5.0 Battery wire relocation Inside Pic request! 1994 - 1995 Specific Tech 2
94GTLaserRC Battery Relocation Kit Questions 1994 - 1995 Specific Tech 35
R battery relocation...problem 1994 - 1995 Specific Tech 11
I Question about battery relocation kit.. 1979 - 1995 (Fox, SN95.0, & 2.3L) -General/Talk- 5
Similar threads