New battery tray vs trunk relocation

Discussion in 'Fox 5.0 Mustang Tech' started by billison, Mar 8, 2013.

  1. Okay, as im getting close to diving in and doing my 3 G alternator swap one of the things I realized I need to address is my battery. My battery tray is all kinds of broken. After shopping online, I found that a new battery tray is going to cost almost as much as a battery box and the Wyer I would need to relocate to the trunk.

    I have no plans in the foreseeable future of going to the track, so if I did a battery relocation I would have no plans of installing the cut off switches.

    So my question is, can I simply installed the battery in the trunk inside a sealed box and run the longer positive cable from the trunk to the solenoid, and from the negative to the frame in the trunk without issue?

    Am I right that I will need 2 gauge wire Or lower to relocate?

    I would be relocating primarily to improve the looks and to get the battery out of the way.

    If I can't do a simple battery location, I'll just buy a new tray, but I really like the idea of relocating it.
  2. Most OE-type batteries emit toxic fumes, hence why they are located in the engine bay and not in the passenger compartment. Unless you replace the battery, it would be a good idea to use a sealed case vented to the atmosphere.
  3. Well.. That's one mark against
  4. 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.


    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 [​IMG]

    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.

    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
  5. Don't understand why you don't just go to a JY and for $5 get another stock battery tray. Problem solved.
  6. If i can find one is the question...
  7. i saw 3 last weekend at UPULL it. Go on the Corral and post a WTB if you can't find one.
  8. I like the battery in the trunk, it moves the center of gravity rearward, improving traction and handling. It does eat up some trunk space, but I'm willing to give it up. I grounded the battery in the trunk, and just ran the one conductor forward. Years later when I dyno tuned the 89, my tuner insisted I run a separate #10 ground from the battery up to the computer ground jrichker mentioned.
  9. this +1

    They sell battery boxes that have vent tubes. You drill a small hole in your trunk and run the tube through there. Simple.
  10. What size for the main run did you use?

    It's a convertible , think I can run the vent tube facing down?
  11. I was also looking to minimize weight, so I ran a #4, from the positive terminal of the battery in the trunk to a newly installed second solenoid on the passenger strut tower, so that the conductor run was shorter. I then ran a #10 from the original solenoid starter terminal to the new solenoid control terminal, and ran a shorter starter conductor from the starter to the new solenoid on the passenger strut tower. After a couple days of so-so starting, I switched to a mini starter (which draw less amps) and have never had any other issues with it. Been running it like this for many years at this point. You can run the vent wherever you want, though I actually did not use a box.
  12. Relocating the battery to the trunk is not a cheap modification to do properly. You should be using #1/0 cable for BOTH 12V and ground. A dedicated ground should go from the trunk to the engine block, then to the chassis. Some people will tell you that they only grounded the battery to the frame in the back of the car and everything is fine, but that really is not the proper way to do it. Grounds are just as important as hot legs, especially on an EFI vehicle.

    A battery relocation is not worth it unless it's something you really really want to do.
  13. If I do it, I'll go all out.
  14. want me to get you a battery tray if I see one at the U Pull it tomorrow? I'll charge you the cost + shipping.
  15. I'm good for now. I'm just getting info at this point. I gotta buy tires, get tail pipes installed, buy quads, get odd ball parts for my 3G swap, this is further down my list for now. We're finally getting a break in the weather so I might hit my pnp on sat.
  16. Call your ford dealer, last time i needed one was because my battery was in the hatch and i needed the tray to mount the vortech reservoir for my intercooler.

    Went to ford and got one, like $39. That was after reading internet rumors that it didn't exist.

    To do the hatch mount right, it takes more money than you think, i used the tailor kit, but if i did it again i'd do the moroso kit with the plastic box.
    Keep in mind to that when you throw the cut off switch it has to kill the car, that requires another wire, and if you want your radio to keep it's settings, you need yet another.
  17. Cost me around $200 last time to mount my battery in the trunk of the 87 vert. Used a Taylor vented box, kill switch, 0g wire, 10 g wire for the noid, Honestly, unless you plan on dragging or showing the car, that would not be a priority for me.
  18. Yeah. I'm just gonna replace the tray( wanna get me one mike?) and call it a day for now. If I can't do it right ill not do it for now. Thanks for the help guys!
  19. Not heading back to the jy until a week from this weekend as I am putting on an H Pipe and removing the smog pump and hoses this weekend and installing some U/D pulleys. I figure they will charge me about $5-$10 for the tray and another $5 -10 to ship. Worst case you are looking at $20. I pulled one for you last week but I'll be damned if I can remember where I hid it.. lol If you want it paypal me $20 to [email protected] and I will get it and send it to you.

    Your best bet if you want one cheap and quick is to scrounge the Corral for guys parting them out.
  20. A good battery box kit is sealed and it includes the vent tube and wiring. It's a simple install. (like you said, power wire up to the solenoid and ground to the frame)