Trunk mounted battery

[paulv]

Has anyone done a trunk mounted battery? I want to do this on my 92 I have the Taylor kit that I bought years ago. Any helpful hints?

 

[yamahaSHO]

I have a Moroso kit for my setup. It's pretty straight forward. What specific questions do you have?

 

[firebat45]

I've been thinkingabout relocating as well. What's people's opinions on the ground wire? Should it just ground to the chassis as close to the battery as practical or should it be run up to the starter like OEM? Or maybe ground it to chassis then run a thick ground strap from the chassis to the starter at the front of the car?

 

[yamahaSHO]

My battery is grounted to the rear seatbelt.

 

[SHOZ123]

I also use the rear seatbelt location. But also have a #8 wire going to the engine block from the seatbelt anchor location.

Made my own battery relocation kit out of #2 THHN wire. Use the quick disconnects found on industrial batteries. The 175A size.

Just rigged up a mount for a PC 925 in the trunk out of some 1/4" aluminum flat stock.

 

[SHOtime2511]

i grounded mine to the chassis where the bolts from the strut come into the trunk.

 

[sho_ted]

UNLESS its a race car why move it?

 

[frosho]

More room under the hood. Belt changes would be easier without that blasted bracket getting in the way...

 

[yamahaSHO]

UNLESS its a race car why move it?

I had to mount my mechanically driven intake device where the stock battery location is.

 

[Lupo]

Be sure to take the ECU ground and run it back and attach directly to the battery, or you may have strange problems with the ECU.

Also, I would have a fast acting fuse near the battery for safety.

 

[gmorrell]

I had to mount my mechanically driven intake device where the stock battery location is.

You have belt-driven hair dryer?

Lupo has been paying attention. EEC has two power grounds, pins 40 and 60. These need to return directly to the battery negative terminal, preferably as separate 14 gauge wires, don't combine them into one wire. If you dump them into the chassis, and then put the battery 10 feet away in the trunk, the impedance of the sheet metal can noise up EEC and cause it to do all manner of unpredictable sh*t.

EEC pin 20 is just a case ground, an electrostatic shield, it should tie to the chassis near the EEC module as the factory intended.

 

[38SHO]

you can ground the battery right to the chassis, I would run 1/0 cable.... one negative from the battery to the chassis, one positive from the battery to the starter. remeber, power will only be as good as the smallest wire it has to run in its circuit.... if you have 1/0 going to the starter for positive, then a 8 gauge wire for the ground, well your electrons can only move as good as that ground wire, no matter what other wires you have....

I would then run 1/0 wire for a ground from the engine to the chassis where the factory ground goes to the starter bolt.... you might also want to do one from the top of the engine, either the intake or the crossover tube, at 1/0 gauge


I would run these size cables for voltage drop reasons... basically the longer the wire the less power it can flow, wires with less strands in them, poor connections, corrosion... can all cause problems with this

basically all your battery does is provide ground for your 12v systems and provide power for the starter, so by giving a thick power cable from the battery to starter, and thick ground cables from batter to chassis, and engine/starter to chassis... you provide a better path for the power over the longer distance of the cable... think of it as making a nice big wide interstate for your electrons(cars) to travel down... you can flow a lot more traffic on that then a little 2 lane backroad...

please let me know, why you must run those ECU grounds directly to the battery, in fact they will probably work better with a shorter wire grounded to the chassis, then running your small ass 16gauge or 18 gauge wire from the ecu to the trunk.... if you have good ground connections.....

my car has a ground from the battery to the chassis, and to the engine, and thats it... works perfect... a ground is a ground, wether its on your chassis or your negative battery post, as long as you keep in mind wire gauges, and connections/ground contacts... you are all set

if you want some REAL quality cable to run a battery, I suggest using some Kicker 1/0 gauge cables for amplifiers.... It is very tightly wound wire with lots of strands in it... even their 4 gauge wire looks bigger then cheap, china 1/0 wire

 

[gmorrell]

please let me know, why you must run those ECU grounds directly to the battery, in fact they will probably work better with a shorter wire grounded to the chassis, then running your small ass 16gauge or 18 gauge wire from the ecu to the trunk.... if you have good ground connections.....

Perhaps you'd like to speak with a Ford EEC designer about it? Oh wait, I'm one of those designers...

And I didn't say "small ass 16gauge or 18 gauge wire", I said 14 gauge, 12 gauge would be better.

The problem is something called inductance, which is AC resistance, not DC resistance. EEC dumps a lot of high frequency ground currents out of pins 40 and 60 (fuel injector noise, IAC PWM motor noise, ignition noise, etc...), and if you drop those into chassis sheet metal, the inductance of the chassis ground path back to the battery may cause the AC noise level at EEC to increase to the point where it has difficulty discriminating changes in the outputs of engine sensors, this is where you get erratic operation, and I've seen it, measured it, and corrected it in passenger car and racing applications using EEC.

The chassis is generally considered to be a crappy ground path for AC and noise, and it just gets worse as the vehicle ages due to corrosion and separating spot welds, and there's another problem- it's dynamic: As the vehicle drives over bumps and the chassis moves and twists, the impedance changes.

A car battery is a great place to dump AC noise, because it has very low impedance, but if you put chassis inductance between the noise generator (EEC) and the battery negative terminal, noise becomes a problem.

I have no issues with running large gauge copper cables for B+ and ground between a remote battery and the engine, I've done it myself on two rear mounted batteries in my track cars, but this is to get low DC resistance between the battery and the high current DC loads in the engine compartment.

 

[Shoaz]

please let me know, why you must run those ECU grounds directly to the battery, in fact they will probably work better with a shorter wire grounded to the chassis, then running your small ass 16gauge or 18 gauge wire from the ecu to the trunk.... if you have good ground connections.....

Answer from one post above yours:

Lupo has been paying attention. EEC has two power grounds, pins 40 and 60. These need to return directly to the battery negative terminal, preferably as separate 14 gauge wires, don't combine them into one wire. If you dump them into the chassis, and then put the battery 10 feet away in the trunk, the impedance of the sheet metal can noise up EEC and cause it to do all manner of unpredictable sh*t.

EEC pin 20 is just a case ground, an electrostatic shield, it should tie to the chassis near the EEC module as the factory intended.

Electrical noise in ground references (or in the power supply) can really hose up computer-based real-time control systems, like the EEC-IV, that read sensors and things to do their job. An engine computer has a lot of electrical noise to deal with, anyway, given that there's a high-voltage spark ignition system rattling away nearby, sensors that generate noisy signals (like most in a SHO), and mechanical vibrations banging away on all the connectors. Ground noise issues can be very difficult to isolate and fix, so ignore the previous advice from Gary and Lupo at your own peril.

Edit: Looks like Gary beat me to it.

 

[SHOtime2511]

no problems on my chassis ground for the ECU yet,but ill be sure to keep this in mind.

 

[SeanMc]

You have belt-driven hair dryer?

Lupo has been paying attention. EEC has two power grounds, pins 40 and 60. These need to return directly to the battery negative terminal, preferably as separate 14 gauge wires, don't combine them into one wire. If you dump them into the chassis, and then put the battery 10 feet away in the trunk, the impedance of the sheet metal can noise up EEC and cause it to do all manner of unpredictable sh*t.

EEC pin 20 is just a case ground, an electrostatic shield, it should tie to the chassis near the EEC module as the factory intended.

His car looks like something out of NASA.

 

[pitaSHO]

I ran two 2 gauge wires from the trunk all the way to the front. They attach where they normally would if the battery was in the engine bay.

Chris K.

 

[paulv]

Thank you for the help.... this may sound like a stupid question, but what is (are) ALSFB's ? Thanks for helping a dummy out....paulv

 

[TopGunnYFZ]

Thank you for the help.... this may sound like a stupid question, but what is (are) ALSFB's ? Thanks for helping a dummy out....paulv

ALuminum SubFrame Bushings

 

[gsilva]

My battery is grounted to the rear seatbelt.

I did the same thing. I have noticed that trunk mounted battery's stay cleaner. They don't have the corroded terminals like engine compartment mounted battery's.