How to relocate your battery to the trunk

Discussion in 'DIY Tech Guides' started by moooosestang, Jan 22, 2023.

Car Parts
  1. moooosestang

    moooosestang Junior Member

    Things you'll need.
    1. 13 feet of 1awg + battery cable, 2 feet of 1awg - battery cable, some sort of distribution block to connect your positive cables in the engine bay, copper crimp on battery lugs(order 6awg if reusing stock wires, the 4awg are way too big for some reason, chinese tolerances maybe?), crimping tool, some sort of battery hold down for the trunk.

    Maybe order 4 and 6awg copper lugs. I'm not sure if there are variations in the different chinese manufacturers. here's a picture of a 4awg and a 6awg on the stock power wires. see how much larger the 4awg flare is. that's not how it's supposed to look. Either will likely work, but the 6awg fits tight before you crimp.


    Tools you'll need. something to cut large gauge wire. I used a pair of kleins i had. A hand held crimping tool or hammer style crimping tool. I used the hammer type. you can order this with lugs for $8 more,aps,125&sr=8-2-spons&spLa=ZW5jcnlwdGVkUXVhbGlmaWVyPUFTRDAzNFdSTldQQ00mZW5jcnlwdGVkSWQ9QTA5NzIwNzMyTkJTUk1UTVVNWU9SJmVuY3J5cHRlZEFkSWQ9QTA2MzcxMjU2QVlOWE5CTUZCSVQmd2lkZ2V0TmFtZT1zcF9hdGYmYWN0aW9uPWNsaWNrUmVkaXJlY3QmZG9Ob3RMb2dDbGljaz10cnVl&th=1 , but it really requires removing the cables from the car. Not wanting to remove the alternator, ground cables i just placed the tool on the strut tower or in the void where the battery was at and used a 5lb sledge. The correct way is to remove these wires and hammer on a cement foundation. Using the hammer style tool on the car is a pain. All of these tools use pressure to form the copper wire and the copper lug into one sold piece of copper. I did a few tests with some scrap wire and cut the lugs open with a hack saw to insure i was getting good contact. That's not coming loose!


    If you are racing then this post isn't for you. You need a sealed battery box vented to the outside for racing, plus a disconnect switch accessible from outside the vehicle.

    First and foremost don't order cable off amazon or ebay unless you are 100% sure it's 100% pure copper. There are many amazon sellers trying to pass off copper clad aluminum cable as pure copper. If it doesn't say 100% copper then it's not. You don't want aluminum cable in your car. I ordered my positive and negative cables from with the battery ends and lugs all ready installed.
    Some people use 0awg cable, some get by with 2awg cable. I decided to split the difference and ordered 1awg. I've seen people recommend 00awg cable. Dodge uses 1awg cable for their batteries in the chargers so that was good enough for me.

    First step, remove the battery. cut open the factory positive and negative harness. cut off all the factory connectors. No going back now!


    You can completely remove the negative cable running from the battery to the strut tower since the battery will no longer be there. Now is a good time to mount your distribution block. i picked a spot on the firewall as close to the engine as i could get because my initial plan was to use the battery space for a larger intercooler reservoir. From right to left I have my alternator cable, fuse box positive cable, starter cable, then battery cable.


    That's all the easy stuff! The fun part is routing a 1awg cable between the firewall and inner fender, through the firewall and interior of the car. Some people route the battery + under the car. this didn't appeal to me so i had to remove my rear seats and all the lower panels on the passenger side to route the cable under the carpet. there's a rubber nipple on the firewall grommet for the factory wiring harness. You'll need to remove the passenger front tire and inner fender to access it. cut off that nipple and push your 1awg wire through it. I used a little vaseline for lube. I used some heavy duty double walled heater hose as a shield where i fed it through the inner fender/firewall gap. you could use a hole saw and a cable passthrough fitting or even a bulkhead fitting here. i was going for easiest. you can see my red heater hose in the background. this is the factory ground cable with a new copper lug. it runs to the passenger side motor mount bolt. The factory starter cable is in the same wire loom as the ground cable, so if you want to replace the starter cable with a larger gauge it's easier to just remove this whole thing and separate it off the vehicle. this is totally unnecessary though. The stock wire for the starter will work fine. Don't make more work for yourself like I did. Ignore the bread tie, that was temporary. My battery tender pigtail is grounded to the strut tower and positive goes to the distribution block screw. There are small screws you can attach small gauge wire to.


    I'm not going to link the battery hold down i got. it's a pretty generic one sold all over amazon and ebay for optima redtop batteries. If you go this route and don't use a sealed box you really need an AGM battery like the optima. The diehard in the pic will give off hydrogen gas that you don't want to breath. I've since switched to an optima 34/78 800cca.


    If you google battery relocation you'll see all kinds of posts saying to run a negative cable all the way from the trunk to the engine block. Ignore these people. The s197 has a nice threaded hole in the trunk that goes through two solid pieces of the chassis. just take a wire wheel and clean off all the metal. I'm pretty sure that's a m8 bolt. it's a factory bolt i removed from some other place and repurposed. I never throw away bolts. I forgot to mention i bought 1/2 inch braided wire loom on amazon. it offers some protection from chaffing and it looks nice. Don't get more than 2 foot for the negative cable it will just increase resistance. I probably could have done it with a 1 foot negative cable if i turned the battery around.


    I cheated once again mounting the battery hold down. I used two of the shaker 1000 threaded holes. lined one up with the battery tray hold then drilled through the corner of the aluminum tray for the second hole. This way i didn't have to drill through the trunk. If you didn't have a shaker 1000 these holes are covered up with a thick pad. It's much easier to take a small phillips screw driver and punch through these holes from underneath the car. These are also m8 threads and i had bolts laying around that threaded right in. I cut the stock carpet along the spare tire tub line so i could still remove the spare tire cover.

    I'm probably forgetting something. I also took a bunch of video to make a youtube video. I'll try to work on that next. One thing i bought but didn't use was a 200a fuse. I ordered the battery cables without really thinking it through of how i was going to mount the fuse. A fuse close to the battery is supposed to prevent a fire in a direct short scenario with your + battery cable. My wifes dodge charger does not have any fuse that i could see unless it's a fusible link inside the wire. I could add my fuse between the negative lug and the chassis. It should still pop in the event of a direct short. The other option is a circuit breaker.

    here's a closeup of the distribution block. it doesn't come with hardware to mount it. Use some good hardware with lock nuts or lock washers. don't try to mount this with self tapping screws. You need this to not come loose.


    Why move the battery to the trunk? Well, i have a 100lb supercharger added to my motor so this helps offset some of that weight. this is not a weight saving mod. if anything i added weight, but most of that added weight is spread out over the length of the car. Combined with deleting my a/c and the steeda radiator support i can really feel the difference. It fired up on the first try and even with the 600cca diehard it started as quickly as if it were still in the stock location. Changing to the optima makes a very noticeable difference in cranking speed.

    short video of the first start. this was with the stock starter cable and diehard battery.
    Last edited by a moderator: Jan 23, 2023
    XJCasper, crjackson, mpm_1 and 4 others like this.
  2. JC SSP

    JC SSP Member

    Very well done... thanks for the write up buddy.
  3. Cum Grano Salis

    Cum Grano Salis Member

    Do like your work. Only thing I found over years with my own screw-ups is if the home crimps aren’t double done and soldered, heat can expand and contract things making them loose. Aluminum wire was horrid… could get as tight as possible, come back and retighten screw terminal lugs half turn again maybe an hour or less later. Cu much more stable, no AL in auto wiring (yet). Now I’m relaying my own findings only, no criticism on anything in threads here.

    Very few use the heat shrink and split-loom with projects as such and to use firewall buss strip for wire connection/terminations is ingenious. Wouldn’t have thought on that, still on curve myself. Only thing I’ve lived longer for more things to happen not going as planned.
  4. moooosestang

    moooosestang Junior Member

    If you are crimping copper to copper there is nothing to work loose if done right. You are fusing the two pieces of copper into one solid piece. That's why i showed the copper lug cut in half. you can't see any visible wire strands after crimping. Nobody should use screw termimal battery lugs. Not sure why they even make such a terrible part. Also solder is not going to wick into a solid piece of copper after crimping. Someone on youtube tried that and failed to get solder into a crimped joint. Crimping is superior to soldering. No car manufacturer solders any battery connections.
  5. pass1over

    pass1over I like it LOW


    crimping is also way cheaper and easier. Both can be done poorly though and create a bad connection.
  6. moooosestang

    moooosestang Junior Member

    It just so happens to be cheaper and easier. This is one case where cheaper and easier = better. Also trying to solder 1awg wire is not fun. 13 feet of 1awg wire carries heat away fast! There is just a greater chance for a cold joint with this size wire. For small gauge wire i solder all my connection and use heat shrink with the glue inside. I build drones as a hobby and love melting metal.
    Last edited: Jan 24, 2023
  7. Cum Grano Salis

    Cum Grano Salis Member

    If you say so, not saying another word.
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