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Battery relocation

3K views 41 replies 15 participants last post by  Rocketdog 
#1 · (Edited)
Can I get some pics of your trunk-mounted battery setups? I'm looking for inspiration. I'm going to be moving the battery to the rear passenger corner and wanted to see how you guys have physically mounted the battery to the car (what style tray/holder) and where have you mounted any fuse/relay panels. I'm not looking for electrical advice, only mounting configurations. Thanks!!

This is my starting point:



 
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#3 ·
Are you building it with track use in mind where you have to meet NHRA rules or just as a general relocation for a street car? I did my relocation on the cheap using junkyard cables from cars with factory rear mounted batteries(Lincoln LS) and simply modified the stock battery tray. Positive runs from the battery to starter then starter to fuse box and negative is bolted to a convenient grounding bolt right by the new location. I use an AGM battery so I don’t see the need for a ventilated box or firewall and I didn’t wire up a kill switch so it’s not exactly tech legal. But I wanted a trunk mounted battery and its benefits and I got it,

Either way I see no need to have the fuse/relay panels relocated to the back unless you’re rewiring from scratch.
 
#4 ·
It's not a dedicated track car but it may see one from time to time and I don't want something like this to be grounds to get tossed. I've already got plenty of 2/0 welding cable for this. I plan to pull from the stock underhood box (if it stays in factory place, idk) to a 300a ANL then thru the car to another 300a ANL fuse and then to the battery. I would pull to the starter from the back, but the firewall hole from my previous car audio install is drilled on the driver side so I'll just go that route.

I'm going to also upgrade the fuel pump wiring to 10ga and add a relay/fuse for that and I figured right by the bettery in the trunk would make sense versus somewhere up front.
 
#5 ·
Did you route down the pass side, and go thru the firewall there?
EDIT: I guess the starter is just on the other side of the floor there.
 
#7 ·
Mine will cross over at the back seat and go thru the driver's side firewall to the main box. I'll go from the underhood box to the starter with 2/0.

I'm trying to figure out a good place to mount the fuses and relay. I'll also have the audio wiring for a monoblock and 4 channel. The subwoofer box takes the entire height up to the deck and leaves about 2" of width between the shocks. Maybe I should use something like THIS.
 
#8 ·
Old setup:



Current setup:


It was NHRA legal before, and it still is of course, as I have an aluminum rear firewall that exceeds the NHRA requirement. I switched to a sealed box a few years back when I went to a typical lead acid battery instead of Optima (Optima is not known for quality anymore).

 
#13 ·
Quality became hit or miss when the company was sold and production moved to Mexico years ago. Prices went up at the same time.
 
#15 ·
Ditto. I used to run them in everything. They were really great batteries in the early 2000’s.
 
#16 ·
I also wanted to shove my battery in the back. I have zero gauge amplifier cable already running to the back there, all I wanted to use was a curcit breaker next to the battery and ground it somewhere gloss to the frame rail. I have distribution post to connect the original battery cables up front to the new power cables running back. I have these





 
#19 · (Edited)
It going in the trunk because the turbo will live (roughly) in it's place up front. It's not a dedicated drag car - may never see a drag strip honestly. This is more of a fun driver that I may shoot around at an auto-x event every now-and-then or whatever. I'm not putting in a rear firewall for sure. I hadn't planned on a cut-off either. I had an alternator built and it benched at 277+ amps so I'm good there also.
 
#22 ·
Standard lead acid batts are easier to care for, and keep in good condition. sla or agm batts are finicky, and neither types will deal well with our charging system hitting130A of charge current. It just makes a standard one need water,lol.
 
#24 ·
I run dual AGM's in my 01 7.3 diesel, work better than anything else I've had in it over the last 22 years. The Optima's in the winter if it didn't start right away would run out of juice quickly. That's when I quit using them.
 
#25 ·
When agm batteries form bubbles, the bubbles can't move, and it decreases the cranking amps, or total power.Same thing with gel cells.Bubbles in standard batts just float to the top and pop.
 
#27 ·
I will try to get some pictures for you.
I did this mod as one of my very first, so it has room to grow. While I intend to put in the NHRA legal box and kill switch, for now it's still a street car application.

I used a battery tray from AutoZone and bolted that to the right side trunk floor, through the carpet. The battery is held in place with universal hold down j bolts. I used a plexiglass panel to cover the battery to prevent a crowbar incident. The plexiglass is also a great spot to bolt in a fuse or breaker panel and a local disconnecting means.

I ran my positive connection from the engine bay fuse panel to a hidden 300Amp 12v disconnect switch in the jockey box, and from there to the battery. In hindsight, I should have gone to the starter and then to the fuse panel. I am a fool for grounding and bonding so my negative wire goes from the battery to the engine block, with extra grounds locally in the trunk near the battery. I also ran a bond from the engine block to the firewall.

I ran all my cables through the OEM wire tray where possible, penetrated the firewall at an existing gland. From the jockey box to the battery, the POS wire lays under the back seat. I put this section inside a garden hose for added protection. Don't run your wires outside the car, especially beneath the car for obvious reasons.

I was really surprised by the handling difference this made to my car. I upgraded my suspension, steering, wheels and tires after the battery relocation, so I did get a good comparison. The car feels lighter and the front stays well planted without any pushing. It feels safer, more solidly connected to the road in turns.

Incidentally, I did this before I re-geared and added traction lock to the car and it made a big improvement in traction. My car used to do the one wheel peel or with trac assist on, fight with itself trying to launch. Neither was good. Moving the battery allowed me to shut off the trac assist and get both wheels to spin better than previously.

I don't drive my car in snow, but I imagine it would help there as well.

I like to run two batteries in boats and trucks, with the appropriate bat 1, bat 2, both switch. This allows running an inverter without concerns.
It seems like too much added weight for the Cougar to have 2 batteries without obvious benefits. I have taken some weight out of the car with the engine swap, RLCAs, diff housing, etc.




 
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#28 ·
I was really surprised by the handling difference this made to my car. I upgraded my suspension, steering, wheels and tires after the battery relocation, so I did get a good comparison. The car feels lighter and the front stays well planted without any pushing. It feels safer, more solidly connected to the road in turns.
It reallly made that much of a difference?? I really wanted to try this out next weekend. Only trouble I have is where I should run the ground wire.
 
#31 ·
MSC and mcmaster sell a bulkhead passthru called a sealcon, and those have a rubber insert that makes a seal for water ingression protection,I use those.
 
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#32 ·
This is how I did the bulkhead passthrough - note this won’t work on 89-95s with ABS as those use this hole for wiring. Though the“grommet” in this case is a modified abs harness boot, the center is a cut down hockey puck with the cable fed through




This is where the cable grounds


 
#33 ·
That's where my amp is currently grounded. I pulled out the 2awg wire and started to get it ready to go in. I weighed the other cable, a 30' length is 100lbs. of solid copper, lol.
 
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