mounting a battery in the trunk

grumpyvette

Administrator
Staff member
one very common performance car modification for muscle cars involves moving the battery from up near the front wheel well to the drivers side trunk, to increase traction and free up engine compartment space.
your normally removing about 40lbs from the front and moving it to the rear, that factor alone tends to improve traction.
you'll normally want to use some COPPER welding cable of about 1/0 gauge for the positive cable that goes to the starter, but mount a disconnect switch and enclose the battery in a non corrosive box and mount an easily accessible cut off switch, to disconnect the positive main battery feed to the car,the switch is required to be external and labeled on race cars so check your rule book,the battery needs to be bolted securely into a bracket or frame, and a non-corrosive plastic box in a metal frame is preferred,and ground the negative 1/0 copper lead to the cars frame and a second 4 ga to the body of the car, plus run a separate ground cable of at least 4 ga to the engine block.
AND yes obviously the QUALITY and CARE taken in battery selection and maintenance MATERS, as does the company GUARANTEE
http://shop.advanceautoparts.com/p/...080024-P?searchTerm=optima+battery#fragment-3
startersolenoid.gif
btw if you try to slide a battery cable through the protective flex electrical conduit spray it liberally with WD40 it makes it slide far easier


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ID verify with the track officials but last time I checked Battery cables and all wiring can be run inside the frame rails.
(ideally with plastic tube condit to reduce any potential vibration chaffing )
and fuel , oil, coolant or brake or any fluid lines must be outside the drives compartment


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read thru these
http://www.jegs.com/i/JEGS-Performance- ... Id=1359671
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Relocating a battery to the trunk

There was mistake on two of the diagrams ( "Battery in the trunk" and "Battery in the trunk with master cut-off switch" ). A 125A fuse with 4 gauge cable should be used instead of 50A and 8 gauge. Thanks to Vonore TN for pointing that out.

This question gets asked from time to time. I rarely read good answers. The following is a compilation of tips to move the battery to the trunk.

Basic stock diagram which has been simplified for sake of explanation

Here are some tips to do this:

1. DO NOT do (like some) and run a large gauge cable directly from the battery, through the floor and to the starter. Hack jobs are done like that and it is a recipe for a fire. Buy a solenoid kit (Summit # SUM-G1750 or similar)
http://static.summitracing.com/global/images/instructions/sum-g1750.pdf
sum-g1750.jpg

and mount it in the trunk and use it as a switch to let current flow to the starter when you start the car. The solenoid will disengage and cut current off as soon as you release the ignition key after the engine starts. With this setup, the positive battery cable is only HOT when the key is turned to "START". To control this solenoid, you have to buy a small 30 amp relay ($5 at most auto parts store). This relay is energized by the wire that used to go to the starter solenoid. Make sure you use grommets where any cables go through sheet metal. Very important. I cannot stress that enough.

2. Do Not "Jump" the starter solenoid from the battery cable. This picture shows this common setup (similar to the one shown by Buffhomer who posts on the Corral.net). With 1993 and later Mustangs that is not a good idea since they use permanent magnets in the starter motor. The starter motor pinion could stick to the flywheel after your release the ignition key. Not good. So follow the proper setup.

3. If you go racing, some tracks or sanctioning bodies may require a Master cut-off switch because you moved the battery. That makes the diagram a little more complicated. See this diagram for the setup. You have to use a "four terminal" master cut-off switch (Taylor #1033 or Moroso 74102) and an alternator cut-off switch (Painless #50105) to cut-off the juice from the alternator AT THE SAME TIME as you cut the battery. If you do not do this, the voltage will spike (18+V) and damage the ECU or ignition. This happens because the battery acts like a stabilizer in the electrical system. Without it, the alternator will try to compensate and Boom. Bye bye ignition and ECU. Very expensive mistake. The Painless #50105 must be switched via a relay so that you do not drain the battery when the car is not running. Find a circuit that is HOT in START and RUN and tap from it to energize the relay. By the way, the Moroso switch is a little on the overkill side with a 300A continuous rating. The terminals are also designed for 1/2" lugs. That is larger than standard (3/8").

4. For #3 above, this is not well documented on the internet. I suggest you follow my recommendations.

5. Breakers: Some people try to get away from using a trunk mounted solenoid by using a large amp breaker on the + cable. These have become very popular over the years because of the big sound systems. I have never tried one. But keep this in mind: the starter motor needs a LOT of current when it is very cold outside. So the current draw could exceed the capabilities of a 150A~200A breaker. You could end up with a breaker that trips all the time. Not fun. I recommend you use a solenoid. MAD Electrical is another source of kits for remote battery installation.

6. These diagrams are for reference. The key to avoid shocks, shorts and fires is proper wiring and good connections. Large gauge cables should be soldered to their terminals (crimping is not enough). Use flux to clean the copper and use good heat shrink tubing. The good heat shrink tubing will produce a "goop" that seals the terminal when it shrinks. The goop oozes out and solidifies. Very good stuff and it is sold by Napa auto parts stores. The stuff at Lowes or Home Depot is designed for home electrical and is not designed to handle road salt environment.

7. Proper grounding is supremely important. If not done properly you will get strange behavior from electronic components in the car such as radio, ignition, etc… DO NOT simply scratch the paint off and drill a hole to bolt the negative to the chassis. That is not a good connection. Trust me. The proper way is to WELD a 3/8" nut to the chassis and bolt the negative cable to that. One in the engine compartment and one in the trunk area. Once the cable is bolted, cover the weld, cable terminal and bolt with dielectric grease to prevent corrosion. Very important to avoid corrosion. If anything replace the stupid flat RED ground strap that Ford uses to ground the motor. What a piece of junk! It is bolted to the frame using a self tapping screw. Also junk. You should use a good 4Gauge cable and bolt it to a welded nut or to the sway bar bracket. This strap left me stranded in the middle of Ohio one Saturday, 4 years ago. The terminal on the red strap tends to crack if overtorqued. Junk!

8. I am very anal about fuses. I fuse everything that goes through sheet metal (except the main battery cables, that task is handled by the solenoid). Fuses are cheap, don’t skimp on them.

9. Most sanctioning bodies require that the battery be placed in a box. Prepare accordingly and make sure you use the same 3/8" threaded ROD to bolt the box AND the battery through the floor (that is required by NHRA anyway). Use a large thick washer under the floor to prevent the battery from pulling through the floor in an accident. Rods with a J hook at the end are not usually accepted at the track. By the way, I do crash testing for the Big Three and I'm telling you that a 30lbs battery can do some serious damage if it comes loose in a crash.

10. 1Gauge battery cable is fine to handle most jobs. 2 Gauge might be a bit small. 1/0Gauge is overkill, but if you like to over design by all means please do so. Just keep in mind that larger cables require larger connectors and terminals and they are not always easy to find.

11. Welding cable is not designed to live in the harsh environment under a car (at least not the stuff I have seen around here). Buy proper cable from Taylor or other. Those cables have the correct sheating to withstand the heat and cold. For the positive cable at the starter motor, make a small bracket to hold the cable to one of the transmission bolts (using tie straps). This will strain relief the cable and not put the connector on the starter under constant load when the motor bounces or torques.

12. With enough patience and a fish tape, you can use existing holes in the trunk to route the cables and wires to the starter. It's a good idea to cover the wire bundle with convolute or protective plastic tubing. Again, use grommets to prevent a short.

Parts needed:
Battery box (sealed)
Wiring kit for battery relocation
Summit SUM-G1750 or MAD Electrical or similar Remote Solenoid kit
General purpose relay

For racing you ALSO need:

Painless #50105 Alternator cut-off switch (solenoid)
Taylor 1033 or Moroso 74102 master cut-off switch

http://www.summitracing.com/parts/MOR-74102/
mor-74102.jpg


http://static.summitracing.com/global/i ... 2_inst.pdf

Welding-Cable.JPG

WELDING cable is far more flexible than standard power cable

wire46.jpg

wiring45.jpg

IMG_4079.jpg


this looks like it needs a non-corrosive box to contain acid spills but otherwise looks like a good install



As you can see, this is a lot of work.

Disclaimer: The result of your project is your responsibility. I only offer recommendations. Someday I will do a complete write-up with pictures.

a great many electrically conductive surfaces are subject to oxidation and corrosion especially things like battery grounds on frames and the newer screw on the side battery cable connections, and battery to starter connections, that might be subjected to water or moisture, so coating those higher amp rated connection points with a good anti corrosive, and moisture resistant and electrically conductive paste , grease or anti-seize would seem to be a good idea.
I know I can,t be the only guy that used to occasionally find when I hit the ignition key and got a click but the starter would not work, and found that a loose battery connection on the cable was at fault! and you might be amazed at the powdered and oxidized surfaces I see on battery and electrical ground cables.
coating those surfaces with electrically conductive grease seems to always reduce those electrical issues

$_35.JPG


http://www.2spi.com/catalog/vac/silver-filled-grease-techdata.html

http://www.cool-amp.com/conducto_lube.html?gclid=CNKs1MD-sMYCFZKBaQodGswC6A

http://www.w8ji.com/dielectric_grease_vs_conductive_grease.htm

http://www.carid.com/loctite/copper...Put_9z-sMYCFQGGaQodOMID_Q#product-details-tab

41VTDWZZPNL.jpg


related info in these links

http://www.madelectrical.com/catalog/st-1.shtml

http://hotrodhotline.com/md/batteryintrunk/

http://hondacrx881.tripod.com/batteryintrunk.html

http://www.2quicknovas.com/trunkbattery.html

http://www.jegs.com/c/Switches-Batterie ... 2/10002/-1

http://www.fordmuscleforums.com/other-a ... y-box.html

http://moldyrabbit.com/liquid/battery.html

http://www.rbeelectronics.com/wtable.htm

http://www.madelectrical.com/catalog/tm-1.shtml

http://www.ehow.com/how_5476457_wire-tr ... ttery.html

viewtopic.php?f=87&t=3174&p=8458&hilit=battery+trunk#p8458
 
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Yes - this was another one of the projects I had in mind.

Why can't you simply put cut off switch on batt ground?

D
 
the race track rules on most tracks specify the cut-off switch MUST be located close to the battery, on the positive lead .because in an accident, its very likely that the insulation on the positive battery will be damaged causing a major fire hazard if it shorts to the car body , cut or short out the negative leads and either nothing works or theres no dangerous effects, that's not true in all cases with a short to ground on a positive batter lead, thats why most tracks say you need to place the switch on the rear near the battery

http://garage.grumpysperformance.co...ardent-jump-suit-sfi-helmet-extingisher.1986/

http://garage.grumpysperformance.com/index.php?threads/fire-suppression.15203/

http://garage.grumpysperformance.co...-fire-extinguisher-handy.81/page-2#post-42551

batdis1.jpg

batdis2.jpg

batdis3.jpg


https://www.hotrodhotline.com/content/installing-battery-disconnect#.XGbr2ehKi9I

https://www.summitracing.com/search/part-type/battery-disconnect-switches?tw=battery disconnect&sw=Battery Disconnect Switches



https://www.jegs.com/i/Flaming+Rive...MIx4qdz5a-4AIVxp-zCh16HwZ2EAQYAyABEgJrAPD_BwE

https://www.hotrodhotline.com/content/installing-battery-disconnect
 
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