legacycentral bbs

A common practice in bmw 320i's is to take the battery from the front left of the engine compartment and move it to the trunk, securing it to the rear strut tower bar. Topend Performance made a bar with this in mind, but it couldn't be too hard to fabricate something. Evidently the move was pretty effective; you improve your weight distribution and take a load off the most overloaded corner of the car.

I'm just tryin to generate ideas.

This is an idea that has intrigued me for a while now. I'm not sure what else is involved other than running another 4 or 8 gauge cable down the length of the car. Where does it get grounded? I assume somewhere in the rear?

-Brian

Generally people also switch to a optima battery (no gas), or use a special box that vents outside of the car. Pretty much all you do is run a large pos calbe to the trunk, then ground to the rear frame i imagine

Mk

mk750 wrote:Generally people also switch to a optima battery (no gas), or use a special box that vents outside of the car. Pretty much all you do is run a large pos calbe to the trunk, then ground to the rear frame i imagine

Mk

320's? this has been done on every performance car known to man. trucks too LOL. to do this on the cheap you can use welding cable available from welding shops and other places Im sure. actually any large gauge cable will work. you can just ground it to the body but you gotta remove paint for a good connection and then paint back over it so it doesnt rust. As far as venting, mk750 is correct. I dont know how you would rig a vent on a wagon that was still streetable(why would anyone make a race wagon) so Id go Optima or similar. those are really strong batteries too.

You run at least 2 gauge wire from your starter to your trunk just like they run a big cable for sound systems. In fact if you have cable run for a sound system all you have to do is fish the one out with the new cable tied to the old. I grounded mine under one of the rear bumper bolts.

2 gauge is HUGE! Isn't that overkill? I've got 4 gauge stereo cable running to a distribution block under the drivers seat. After that's it's all 8 gauge. I know this means nothing in terms of wiring for the car electrical system though. I've also heard of people running the power wire under the car and then up into the trunk when relocating the battery. Has anyone done this?

-Brian

Even 4 gauge cable running all the way from the trunk to the starter will cause a noticable voltage drop when cranking or charging. Consider that starting takes at least 50 amps, and that peak charge current is also close to 50 amps. 0 gauge wire is normally recommended for batteries relocated to the trunk.

I'd need wire with really good (thick and sturdy) insulation before I'd even begin to consider running it under the car, what with all the exposure to weather, moisture, gravel, and dirt. :shock: That wire has the potential to carry enough current to start melting parts of the car.

You run the cable underneath the side step beside the seats where the door closes. 2 gauge is a good size, but I definitely would not go any smaller. 0 gauge might be hard to run inside the vehicle.

I have already done this, by the way... there is a pic of it in here http://bbs.legacycentral.org/viewtopic.php?t=1029.

vrg3 wrote:Even 4 gauge cable running all the way from the trunk to the starter will cause a noticable voltage drop when cranking or charging. Consider that starting takes at least 50 amps, and that peak charge current is also close to 50 amps. 0 gauge wire is normally recommended for batteries relocated to the trunk.

I'd need wire with really good (thick and sturdy) insulation before I'd even begin to consider running it under the car, what with all the exposure to weather, moisture, gravel, and dirt. That wire has the potential to carry enough current to start melting parts of the car.

thats true about the 4g now that I think of it. a cable that long will always cause a drop but a bigger cable wont be as much. get a cheap ohmeter and test a few different cables. Id recommend welding cable for a stick machine, those have to flow 220v charge, and be moved all the time. they are durable and good efficiency.

Reminds me of a story a guy I know told me. He used to work on racecars back in the day, and there was one that had a lot of electrical problems, especially trouble starting. It had fairly long battery cables so he figured they were the problem. Well, a friend of his who worked at NASA had some nice cable lying around that wasn't being used (I think it was meant to be used on some kind of rocket) and offered it to him. He took the thumb-thick orange-insulated cable and hooked it up and it worked beautifully. One day another person (presumably a NASA scientist or something) was looking over the car while he worked on it, and asked if he knew what that orange cable was. My friend says, "No, but it works really well." The guy goes, "It'd better work well! It's pure silver!" Musta been worth a fortune.

whoa nice

EDIT: What I meant to say was, tell your friend to get us hooked up with some nasa schtuff

I think that was about 40 years ago. Now he's primary systems manager for Cornell University's Program of Computer Graphics. :)

thats crazy! I knew gold was highly conductive but not silver!

Gold's not actually that highly conductive. Copper is a better conductor than gold. The reason gold is used on some electrical contacts is that it is less reactive, so it doesn't corrode as easily.