Moving battery: cable sizing, grounding ?'s

If you really want to shorten the braking distance then there are a couple of simple tricks that might provide some improvement. Moving a

20 pound battery from the front to the rear will have NO positive impact on braking distance, nor will it have any measurable (positive or negative) effect on handling.

The tricks for shortening braking distance are as follows:

1. Make sure your braking system is in top condition, properly bled, using manuracturer pads and ABS if installed is fully functional.
2. Make sure you have the proper size tires on all 4 wheels, that they have good tread left and are inflated to the proper pressure.
3. Make sure your suspension system is in top condition as well with shocks and/or struts operating properly.

Moving a battery from front to rear is a complex task that could be expensive and might result in an inoperable car and possibly damaged electronic components if you screw up the ground. Before starting this project I think you need to list both the real measurable benefits and compare them to the extensive list of costs and risks.

Then this is a bad idea. Wiring has weight. Especially the gauge of wiring that will be required here.

You can tell the gauge by looking at the gauge there now. That will tell you how to fuse it as well. I wouldnt worry about the engine controller. I suggested alternator and starter because these are heavy gauge wires and could reduce the size of your main Jumbo wire.

You can probably get an electrical manual for yoru vehicle from HELM. and redesign the power distribution system to be rear battery. Overall this will increase your vehicle weight though.

Alternator has to be seperate because its use is special. I doubt engine controller is seperate. Wouldnt make sense. Starter is always dedicated because its so big.

Rear batter vehicles, and I believe Cadillac has one, will have rear Power Distribution centers so they can fuse the wires right away. (You can drop the gauge of a wire after you fuse it, reducing weight) Note that the cost of wiring tends to be associated with the operations performed on it and not the size of it. smaller wire primarily saves weight, and secondarily cost.

However, rear battery vehicles will also bring the wiring into the passenger compartment right away. They wont go under body to the front and distribute from there. Typically you want your PDC right next to the battery. Some Toyotas even put it right onto the battery.

Moving the battery to the rear will not affect your braking distance in any measurable way. Want to shorten the braking distance? Find and install upgraded brake rotors and pads, and go to ultra-high-temperature, non-silicone-based DOT 5.1 brake fluid.

New battery bracket Battery ventillation provisions Bunch of extra heavy-gauge wire Insulation for bunch of extra heavy-gauge wire

Weight savings? Negative.

You've latched onto what I'm afraid is a pointless idea based on a misunderstanding of how things work.

and tires. Gotta get some sticky rubber on there. 6 piston calipers and 14" rotors won't make a lick of difference with $29.99 walmart allseason rubber on there. In fact, I'd start with rubber before spending two grand on upgraded brakes or moving around the battery.

Unless of course the OP is the kind of guy who considers a 4" exhaust tip as a valid performance upgrade.

Ray

Well, there *are* perfectly valid reasons for wanting to locate the battery in the trunk... off the top of my head, better F/R weight distribution and/or the desire to reduce polar moment of inertia, and/or desire to locate as much mass as possible over the rear axle. None of which would really be perceptible in a "compact Japanese station wagon" without having the automotive sensitivity of a F1 driver, and each desire would likely dictate a different eventual location, anyhow.

nate

I appreciate all the suggestions, and the criticisms too, although still have no concrete suggestions as to cable sizes. So I will look at sizes used on rear battery cars.

I will be doing test of high speed braking distance before and after conversion. The following four tests are planned, in the sequence noted:

1. No modifications.
2. Battery in rear.
3. Battery back in front, cables to rear still present.
4. Battery in rear.

All testing will use a driver who will not know the position of the battery.

By the way, I wasn't gonna mention it, but since someone brought up changes in polar moment, the battery relocation to rear will actually increase the polar moment, a change that is desirable unless you have the fast reactions of an F1 driver.

Jim

Nate Nagel wrote:

Maintain current cable sizes. The only size you really need to change is the starter and perhaps alternator. You probably cant use 2 wires for the starter so 1 jumbo is your only real choice. If you tell gauge and length of current wire I can give new gauge if you also give new length.

If you enjoy this type of thing, best solution is as I suggested. Move not just the battery but the power distribution center as well. Thats the thing that holds several maxi-fuses and relays.

Its a total redesign of power distribution. Its a really big job. Im with the guys who suggest getting wider tires. If this is front wheel drive I have to wonder about removing weigt from over the driving tires.

You must be my brother. Surely there can't be TWO of you.

Common sense says that any difference will be negligible and not likely to be measureable without some very expensive precision test equipment, and that further, any difference (if you *could* measure it) would be offset by the additional weight of the extra wiring. If you were able to accurately measure any changes, considering the weights involved you would also have to adjust your testing to account for whether or not the driver has taken a crap before the tests.

If you really want to waste that much time and money you can pay me to let you come over and cut my grass and rake my yard. At least then you'll get some results you can actually see.

Have you considered what this will do to the warranty on your car?