Battery Relocation to the Trunk......

[Loco1234]

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.

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) 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. 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

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. As I plan to do something similar myself....
__________________

[MM_BKK]

I have a stupid question. If the main battery cable only gets energized when the trunk mounted solenoid is activated upon starting, how is the fuse block getting powered which would supply power to remote keyfobs system, security system, EEC, and not to mention the starter circuit? Do I have to run another positive cable under the car?

[Power Surge]

I really don't agree with a lot of that. When I get some free time later, I'll post why.

[Power Surge]

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) 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.

Riggghhhhtttttt........ My guess is the guy who wrote that, is talking about a different make of vehicle. Even still, I am not getting what's he's really saying. He says don't run a hot cable from the rear batt to the starter in the front of the car. Huh? You HAVE to have a hot cable from back to front, otherwise you'll have no power :). So what does it matter if it's going to a junction box or to the starter (some cars have full time hot to the starter with an integral solenoid on the starter). He wants you to put a solenoid in the TRUNK and then run a SECOND wire all the way to the starter. That doesn't make any sense.


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.

Not quite sure what he's referring to here without the pic that goes with it.


3. If you go racing, some tracks or sanctioning bodies may require a Master cut-off switch because you moved the battery. 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").

You COULD do it that way, but that's a LOT of wasted money and parts. You DO need to kill the alternator directly because if you don't the car will continue to run if you turn the cutoff switch off, because the alternator is now powering the car. You have no idea how many cars I see fail tech for this. But there's a way easier way of doing it that doesn't require all that crap above. Just get a standard two terminal cutoff switch. Run the batt + to one side. The other side goes to your power distribution box. This will power everything on the car, EXCEPT the alternator. Then, remove the heavy alternator cable from the power distribution box, and run it to the back of the car. Attach it to the BATTERY side of the cutoff switch. Now when you throw the cutoff switch, you disconnect the battery AND the alternator from the car. So the alternator can't power the car. Keep in mind that you are keeping the alternator powered, but it's just in a loop with the battery alone and not the rest of the car. No extra parts needed and just two lines front to back on the car. I do it this way on all cars that need a cutoff, and it's never given me a problem.


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

I suggest you don't ;) .


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.

Again, this is not really an issue on Fords.


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.

Agreed.


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!

The welded nut is a little overboard, but you can never have enough ground.


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.

Fuses are always important on anything that draws a load. Anytime you have a wire passing through metal, make sure there is NO chance of it being cut or chafed.


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.

You need more than just a "box". For NHRA and IHRA, it must be an approved, SEALED box that vents to outside the car, unless you have installed an NHRA legal firewall behind the rear seat to isolate the trunk from the driver. Currently the blue Moroso battery box is the most legal version. Jegs make their own copy of it in black, but it doesn't have the quick release pins on the cover. The box must be secured to the body as described above, and you need to run the vent hose to outside the body as well.


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.

Agreed.


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.

Always do whatever you can to ensure protection from metal contact with the cables. Use good thick grommets and make sure the hole in the body is sized for them. If a cable passes something that it might chafe on, I like to wrap it in heater hose in that area to ensure nothing will rub through it. For those who may not feel comfortable running the hot cables through the firewall (if you run it through the inside of the car), you can get bulkheads that install in the sheet metal and you lug the cable on both sides.

[Joe Walsh]

I have a stupid question. If the main battery cable only gets energized when the trunk mounted solenoid is activated upon starting, how is the fuse block getting powered which would supply power to remote keyfobs system, security system, EEC, and not to mention the starter circuit? Do I have to run another positive cable under the car?

Yes, But the second positive wire can be a much smaller gauge and it CAN be fused.
This wire is run from the battery to the power distribution/fuse box under the hood, like the original battery positive wire did.

As previously stated, You cannot put a fuse in the HEAVY gauge positive cable that feeds power to the starter motor.
The starter motor draws WAY to much current and will trip a fuse constantly while cranking the starter motor.
You want it selenoid controlled so it is only 'HOT' while cranking the starter.

[Drock96Marquis]

Just run one, single, large (say 1/0 or 1 AWG) wire from the 'new' battery location DIRECTLY and only to the input stud on the power distribution box. Also, jsut mount the original starter wire to this input stud as well. This will allow the starter, all accessories, everything to work jsut like stock. But with the battery in a new location.

I would route the wire under the car, tucked VERY neatly and securly along the frame rail. I would also put the entire lenth of the wire in wire loom, and then completely wrap the lenght of the loom in electrical tape.

The only time it will pass throught sheet metal is going into the trunk, use a grommet and seal it with black RTV as well.


Use a box with a battery vent that can be routed out the car, otherwise use a battery which doesn't produce gases (ie optimas iirc)


I would also use a fusable link, or two fusable links in unison right after the battery, before the main wiring stretch. This will prevent an electrical fire should a short occur from a crappy install (:P) And will also keep the wire live at all times so the accessories still work properly (which with any type of solenoid setup, shutting off the power to the lead, would not) HOWEVER, the starter may blow the fuse link when cranking. So I woudl just do a very neat and tidy, proper install, and possibly skip the fusable links.

Here is a good guide, can be doen the same way in your 03-04s, but i would also wrap the wire in tape/loom which the author did not:
http://s95318876.onlinehome.us/liquid/battery.html

[Joe Walsh]

Just run one, single, large (say 1/0 or 1 AWG) wire from the 'new' battery location DIRECTLY and only to the input stud on the power distribution box. This will allow the starter, all accessories, everything to work jsut like stock. But with the battery in a new location.

I would route the wire under the car, tucked VERY neatly and securly along the frame rail. I would also put the entire lenth of the wire in wire loom, and then completely wrap the lenght of the loom in electrical tape.

The only time it will pass throught sheet metal is going into the trunk, use a grommet and seal it with black RTV as well.


Use a box with a battery vent that can be routed out the car, otherwise use a battery which doesn't produce gases (ie optimas iirc)


I would also use a fusable link, or two fusable links in unison right after the battery, before the main wiring stretch. This will prevent an electrical fire should a short occur from a crappy install (:P) And will also keep the wire live at all times so the accessories still work properly (which with any type of solenoid setup, shutting off the power to the lead, would not)


What size/rating fusible link would you recommend?

What do you do when your fusible link(s) blows while cranking the starter on a cold morning??

I'll take the time to do it right and avoid arc-welding my Marauder into a smoldering pile of ashes.

Remember Murphy's law and the fact that the Titanic was composed of many water tight compartments...

[Power Surge]

Just run one, single, large (say 1/0 or 1 AWG) wire from the 'new' battery location DIRECTLY and only to the input stud on the power distribution box. Also, jsut mount the original starter wire to this input stud as well. This will allow the starter, all accessories, everything to work jsut like stock. But with the battery in a new location.

I would route the wire under the car, tucked VERY neatly and securly along the frame rail. I would also put the entire lenth of the wire in wire loom, and then completely wrap the lenght of the loom in electrical tape.

The only time it will pass throught sheet metal is going into the trunk, use a grommet and seal it with black RTV as well.


Use a box with a battery vent that can be routed out the car, otherwise use a battery which doesn't produce gases (ie optimas iirc)


I would also use a fusable link, or two fusable links in unison right after the battery, before the main wiring stretch. This will prevent an electrical fire should a short occur from a crappy install (:P) And will also keep the wire live at all times so the accessories still work properly (which with any type of solenoid setup, shutting off the power to the lead, would not) HOWEVER, the starter may blow the fuse link when cranking. So I woudl just do a very neat and tidy, proper install, and possibly skip the fusable links.

Here is a good guide, can be doen the same way in your 03-04s, but i would also wrap the wire in tape/loom which the author did not:
http://s95318876.onlinehome.us/liquid/battery.html


You still need to kill the alternator.

[Drock96Marquis]

What size/rating fusible link would you recommend?

What do you do when your fusible link(s) blows while cranking the starter on a cold morning??

I'll take the time to do it right and avoid arc-welding my Marauder into a smoldering pile of ashes.

Remember Murphy's law and the fact that the Titanic was composed of many water tight compartments...Read my post above, right after what you stopped quoting me at, I said that the fusable link(s) can blow on cranking, so they may need to be skipped. It would have to be a HIGH amp fuse-link to survive cranking, or multiple fuselinks in parallel

Many OE systems work as I described above, especially on foreign cars. The battery cable is routed from the trunk to the underhood, where it is then routed as needed.

Or; like said in the above posts, you could always run two cables, one to the power distro box which is covered using fuseable links. Another, with no fuse-links, but with a solenoid just after battery goes straight to the starter. The solenoid can be powered whenever the ignition is turned to start (note a slight starter lag would result, nbd though)


You still need to kill the alternator. My post was in regards to the battery relocation, unless you are going to the track, the master/alt disconnect stuff is not needed and likely to cause a problem later on, especially on a d/d (I can picture someone playing with the knob and you have a mystery no start :P)
The original post said:
"The following is a compilation of tips to move the battery to the trunk."

If you're not going to the track, then a lot of that is not needed. Not everyone is going to the track, so NHRA,IHRA, NRA, NASA, IRS w/e rules won't be necessary :P

But, if I had to, I would most likely do as the first post said and just use a solenoid.

Adding more, and more solenoids to the system, does add more failure points with them, though.

[David Morton]

Lots of good ideas that sound good and look good on paper. Some aren't so good in practice though. And some are really not neccessary, like the solenoid thing. Just make good holes, grind off the sharp edges, use grommets and shield the cables with a loom or better yet a fiberglass cloth sock/tube. And route them with patience and aforethought. Don't just take the shortest route. Take the safest route.

One thing you alluded to but didn't make a point of was the type of cables to use. In fact you said to not use the best type of cable for DC voltage. AC current likes to travel inside the wire, hence the 19 strand cables running 240V to your house. But DC current likes to travel on the surface of the wire. That's why welding cables have the fine wire cables with thousands of strands. The sheathing may not be suitable for automotive apps. but the idea of fine strands is the right idea for a DC system, the finer the better.

For cable end-lugs use the socket type. After soldering or crimping the cable into the socket, melt on the heat shrink and you'll have a permanent seal against moisture. This will protect the surfaces of the strands from corrosion and keep resistance at a minimum.

FYI: Electrons come from the negative post on the battery where they are all charged up and full of vim and vinegar, so-to-speak. Then they go do their work and come home to the battery all tuckered out. So positive cables need to be at their best. Grounds (negative) are less demanding. Try this experiment. Loosen the negative clamp from the battery and remove it from the post. Then just lay it on the post, just so it touches. If the battery is good, it will crank the engine! You'll never get away with that on the positive.

However, grounds get overlooked in three ways. One you mentioned, using a self-tapping screw, often onto a painted surface.(?)

Two, the ground lug is often just crimped onto the wire, which would be OK if they were both steel, but they're not. The wire's always copper and the lug's steel, and if the lug's copper, you'll be bolting it to steel. These dissimilar metals start a process of electrolytic corrosion where they touch each other whenever water is present. That's why you shoud use the socket type lugs on the cables. This problem is not a big one to overcome, just solder the grounds. Electrolytic corrosion will start where the solder ends and the wire begins but it takes decades to eat through the wire. Soldering keeps out the moisture and that's all it does. It does not decrease resistance. We solve resistance problems with the Ground Triad.

Three, the ground triad. Everybody seems to know to put a ground from the battery to the engine and a ground from the battery to the chassis. But it's often not seen how there can be a benefit from a strap connecting the engine to the chassis. Well I'm here to explain why it IS needed.

There is about one-half OHM of resistance at every connection, a little less as you get closer to the negative side. Modern engine controls like the TPS (it sends a 0-5 volt signal to the computer) send data to the computer and the accuracy and consistency of that data make the difference between an engine that runs OK for a few years and one that gives you 500,000 miles of trouble free consistent performance. When the data ground for these sensors has to go to the computer through the chassis grounds to the battery terminal and then through the engine ground cable to the sensors they lose some power going through all those extra connections, plus all those connections have to be double-plus good. But when the chassis-to-engine strap is used, the computer ground is the same as these sensors and more reliable data results, redundancy is a side benefit, but it's not the main reason. Assurance of equal voltage potentials for the computer and it's data inputs is why the engine-to-chassis strap is neccessary. You can get away without it, for a while. Most manufacturers use them. I've heard some don't hook them up, even though they're there, hanging on the firewall or dangling from a head bolt stud. I've heard some of our Marauders didn't have them hooked up. If you're going to relocate the battery to the trunk, by all means put a strap from the engine to the chassis if it isn't there already. The longer cables make it even more important.

[Loco1234]

Hey thanks everyone so far....
I will soon be undertaking a battery reloaction to the trunk...
Im not sure if Im gonna do it to racing spec but would like to know what addons I would need to do... since Im going this far maybe Ill go the extra mile...

PowerSurge you 100% right this article was written by a Cobra guy....not a marauder guy... pretty similar....LOL

I would like to run my battery + cable up to a post in the engine bay so I can easily jump anothers car etc...
I would like to run the setup off that post very much the same way Ford ran the rest... (well I read addind a negative strap from engine to ground is a great idea so I will add that)
If routed well and safely.... is there any other suggestions out there other than a battery box which I plan to install on the trucks' shelf next to the spare battery....(this way it will be of litle room detriment...)

All ideas and suggestions are appreciated...
I would like to verse myself up on this undertaking before I proceeed...

[O's Fan Rich]

Subscribing... 'cuz I'm doing this.... and I need the info.