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This is a thread on a simple trunk mount battery box. One of the problems with mounting a battery in the trunk is that a simple tray that you can buy at most auto parts stores will not pass tech at most racetracks because the battery needs to be in some kind of a box. A simple marine type battery box will not pass either because it is plastic. My solution is a simple steel bracket that combines with the marine box to give you a simple, cheap safe method of mounting your battery in the trunk or a remote location. This assembly has passed tech as NHRA strips, as well as circle track, mudd bog, hill climb and countless other types of motorsports over the years. If you don't race your car, you can omit the plastic box and use the bracket alone.


You will need a few tools to build this:

-Some way to cut metal- a hacksaw will do, but a chopsaw is better.
-Drill or drill press.
-Welder, a 110 volt welder will do fine.

Here is a materials list:
-30" of 1" x 1" x 1/8" angle iron.
-30" of 3/4" x 1/8" flat steel.
-6" of 1/2" square tubing.
-8-3/8"-16 grade 5 bolts.
-4-3/8-16 nylon lock nuts.
-2-3/8"-16 high nuts.
-Four 3/8" large diameter fender washers.
-1-Plastic marine type battery box.

-I bought the steel out of the scrap bin at of my local metal supplier for $7.50.
-The bolts and nuts were $2.00 at a hardware store.
-The battery box was $8.00 at Wal-mart.

Two pieces of angle iron are cut to 14" in length. I cut them at a 45 degree angle because it looks better. A 3/8" hole is drilled at the end of each piece of angle iron to bolt the bracket down to the trunk floor. The angle pieces are squared up to each other, and a cross piece of 3/4" flat steel is cut to the outside width of the plastic battery box, and everything is welded up:


Two pieces of 3/4" flat steel are cut to 6" in length, and a 1" long 3/8-16 bolt is welded to the end of each piece of flat steel. The uprights are then centered on the base of the bracket and welded 90 degrees to the bottom of the bracket on each side:


Two small pieces of 1 1/4" long 3/4" flat steel are cut and a hole is drilled 1/2" from the end of each piece. These two pieces are welded to a piece of 1/2" square tubing which will serve as the cross bar:


The high nuts are then threaded onto each of the "studs" on the uprights. The high nuts have 1" of thread that will provide adjustability for any battery. Two 1" long 3/8" bolts bolt the cross bar to the high nuts. The crossbar can also be flipped over to provide another 1/2" of adjustability either way:


The box and the lid are both notched for the cross bar to clear, I use a pair of tin snips:



The battery box is placed on the bracket, the battery is set in the box, and the cross bar is bolted down:


The lid is set on top and the assembly is complete. The lid is held down with the nylon strap that comes with the box. Four 3/8" holes are drilled in the trunk floor, and the bracket is bolted in place using the remaining 3/8" bolts with the fender washers and locknuts on the bottom:
 

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Nice job. As usually, very clean and neat workmanship you performed. Just one thing I'd like to interject. You can put the battery in the trunk without a battery box per NHRA rules. There just have to be a "firewall" between the trunk and interior of the vehicle. A piece of sheet aluminum or steel will fulfill that requirement per NHRA rules.
 

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What are the rules for the hold down brackets. I plan to remove the brace from my 67 battery box. Mount it in the plastic box in the truck with a couple 3/8 bolts thru the trunk floor and use the 67 hold down rods and bracket that you use under the hood. Is there a certain size u bolt needed to hold the battery to the tray.
 

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What are the rules for the hold down brackets. I plan to remove the brace from my 67 battery box. Mount it in the plastic box in the truck with a couple 3/8 bolts thru the trunk floor and use the 67 hold down rods and bracket that you use under the hood. Is there a certain size u bolt needed to hold the battery to the tray.

You will need 3/8" hold down bolts.

The stock battery hold downs are 5/16"

Also the stock hold downs are open "J" hooks,the ends need to be closed.
 

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Using a non-sealed battery without a sealed box that is vented to the outside can turn your trunk into a bomb, due to hydrogen gas venting. :shocked:
 

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You can also use a dry cell (AGM) battery like the odyssey or Optima, which is sealed and doesn't vent like the older lead-acid style batteries. That looks well made! I'm always amazed at the creativity and fabrication skills that people here have. Are you planning on using an external cutoff like many tracks require?

I went a different way and got a light-weight battery for the front. The main attraction for me was weight reduction. Although it doesn't have benefits of weight over the rear tires (which the spare tire works well for), I didn't need to fabricate anything, nor did I have live, heavy copper wire running the length of the chassis. My Odyssey 925LMJ weighs 26lbs, is much smaller than stock and has been able to hold a good charge and start the car without trouble no matter what the weather or how long it has sat. It's been going strong for 3 years. I got the metal jacket one and don't leave it out in the heat for long--prolonged exposure to high heat is the main killer for these types of batteries.

Daniel
 

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Personally, I wouldn't put a lead acid battery in the trunk anymore ( I know the Boss 429's had them in the trunk). I would only use an AGM in there. I have an Optima in my car.

Straight from the NHRA rulebook,

8.1 BATTERIES
All batteries must be securely mounted and may not be relocated into the driver or passenger compartments. Rear firewall of .024-inch (.6 mm) steel or .032-inch (.8 mm) aluminum (including package tray) required when battery is re-located in trunk. In lieu of rear firewall, battery may be located in a sealed .024-inch (.6 mm) or .032-inch (.8 mm) aluminum, or FIA accepted poly box. If sealed box is used in lieu of rear firewall, box may not be used to secure battery, and must be vented outside of body. Strapping tape prohibited. A maximum of two automobile batteries, or 150 pounds (68 kg) combined maximum weight (unless otherwise specified in Class Requirements) is permitted. Metal battery hold-down straps mandatory. Hold-down bolts must be minimum 3/8-inch (9.53 mm) if battery is relocated from stock and other than stock hold-downs are used ("J" hooks prohibited or must have open end welded shut.).
 

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heavy copper wire running the length of the chassis. My Odyssey 925LMJ weighs 26lbs, is much smaller than stock and has been able to hold a good charge and start the car without trouble no matter what the weather or how long it has sat. It's been going strong for 3 years. I got the metal jacket one and don't leave it out in the heat for long--prolonged exposure to high heat is the main killer for these types of batteries.
Or you can go both ways, not an ideal picture but a trunk-mounted Odyssey PC925 in the aluminum bracket bolted to a fabricated 1/8in steel shelf mounted to the side of the trunk floor behind the fenderwell.



I obviously wasn't trying to conform to any sanctioning body rulebook, though the battery is substantially enclosed by its mounting bracket when in place and any incident significant enough to break the battery loose is going to crush it anyway.
 

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Not to divert from the thread, but I just removed the stock battery tray from it's angled brackets and bolted it to the rear frame flanges. Then I reused the stock battery hold downs. Can't get any cheaper than that! LOL
Just fine as long as you're using a non-vented or externally-vented battery.

Not that it's quite what folks here seem to be looking at/for but I've had good luck with the blue Moroso trunk-mounted boxes in the past, they're more solid than the marine boxes, have a sealed lid and venting provisions, etc.
 

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Later model Cadillacs have their batteries under the rear seats. Somewhere in the '90's on up. They use a fairly snazzy dual vent cap tube arrangement to vent their batteries outside.
Along the same line Lincoln LS's have their batteries in the trunk. The use a single vent tube that could also be easily modified or extended for Mustang use.
I've pirated one of each from a salvage yards where they are considered next to worthless (IE dirt cheap). I imagine BMW's, Miatas, and such also have some sort of vent system but between the two I have I figure I can use the lead-acid battery of my choice and have a super easy vent setup right at hand.
 

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Later model Cadillacs have their batteries under the rear seats. Somewhere in the '90's on up. They use a fairly snazzy dual vent cap tube arrangement to vent their batteries outside.
Along the same line Lincoln LS's have their batteries in the trunk. The use a single vent tube that could also be easily modified or extended for Mustang use.
I've pirated one of each from a salvage yards where they are considered next to worthless (IE dirt cheap). I imagine BMW's, Miatas, and such also have some sort of vent system but between the two I have I figure I can use the lead-acid battery of my choice and have a super easy vent setup right at hand.
VW Beetles had their batteries under the back seat, lots rusted from venting, acid leakage, etc.

BMWs have had their batteries under the back seats or in the trunk from time immemorial. They've always had builtin venting. My E39 M5 has this giant heavy thing right in the middle of what would be the spare-tire well on other E39s (which have the battery in the right rear fender), I think BMW picked it as much for ballast as for capacity.

Ford put a lot of work into the DEW98 (Lincoln LS) design, they expected it to be their executive-class car in Europe (competing against Es and 5s) so you've got massive amounts of aluminum in the chassis, aluminum front-end sheetmetal, lots of attention to weight distribution like that trunk-mounted battery. They never sold it outside the US, hobbled the powertrains so as not to create in-house competition for Jag, pinched pennies on the trim to try to sell it profitably at a Lincoln price point, but all the nice stuff was absolutely wasted on the average Lincoln buyer. Ford through the '90s is really an object lesson in what could have been.

Miatas from the factory use a little AGM battery that Miata-owning friends tell me is near unobtanium as a service part.
 

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Once upon a time, I worked for Douglas battery (now owned by East Penn)- they made all the "white case" batteries for Mercedes and BMW at the OE level. I was amazed at the elaborate venting setup on a few designs. You'd think AGM would have been part of BMW's engineering vocabulary a long time ago....
The Miata AGM was an oddball. No traditional manufacturer (exide, johnson controls, delphi) made a replacement lead-acid for that one. I no longer recall who made the AGM design for Mazda, but even Douglas' sealed battery line didn't have an app that would fit.
 
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