Moving battery: cable sizing, grounding ?'s

"Jim" > wrote in message
ink.net...
> Jim is answering some of the questions posted:
>
> I want to do it to shorten the braking distance.
>
> It is a brand new compact wagon of Japanese unibody design and US
> manufacture. The battery will be inside the rim of the spare tire,
> under the rear floor.
>
> Everything, including the rear lights, is grounded thru the body - no
> separate ground wires except for a heavy one from the engine block
over
> to the battery minus terminal.
>
> The proposed positive cable will be under the car, with heavy duty PVC
> insulation and covered by the black nylon sheathing typically used for
> car wiring. Small sections subject to movement or slight abrasion
will
> be inside lengths of rubber hose. I have done this before, and have
one
> installation that is now 20 years old with no abrasion problems.
> However, that old vehicle does not have a computer so probably is not
> sensitive to the voltage spikes that occur when you shut off the
starter
> motor. Thus, I am interested in dnoyeB's suggestion to run separate
> hot wires to the alternator, computer, and starter. Any idea what
gage
> each should be? (Would like to keep the weight down.)
>
> Some posters have identified other cars that have the battery in the
> rear. Does anyone know if they run separate wires for alt, comp,
> starter, or take other precautions?
>
> Jim
>
>

Moving the battery isn't going to decrease braking distance. It may
increase it though. Consider that 80% of the braking force of a vehicle
in on the front end of the vehicle.

Also putting the battery in the spare is a REALLY bad idea. If it leaks
you can plan on the spare becoming useless. You also will be voiding the
factory warrantee by moving the battery from the factory location.




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Jim wrote:
> Jim is answering some of the questions posted:
>
> I want to do it to shorten the braking distance.
>
> It is a brand new compact wagon of Japanese unibody design and US
> manufacture. The battery will be inside the rim of the spare tire,
> under the rear floor.
>
> Everything, including the rear lights, is grounded thru the body - no
> separate ground wires except for a heavy one from the engine block over
> to the battery minus terminal.
>
> The proposed positive cable will be under the car, with heavy duty PVC
> insulation and covered by the black nylon sheathing typically used for
> car wiring. Small sections subject to movement or slight abrasion will
> be inside lengths of rubber hose. I have done this before, and have one
> installation that is now 20 years old with no abrasion problems.
> However, that old vehicle does not have a computer so probably is not
> sensitive to the voltage spikes that occur when you shut off the starter
> motor. Thus, I am interested in dnoyeB's suggestion to run separate
> hot wires to the alternator, computer, and starter. Any idea what gage
> each should be? (Would like to keep the weight down.)
>
> Some posters have identified other cars that have the battery in the
> rear. Does anyone know if they run separate wires for alt, comp,
> starter, or take other precautions?
>
> Jim
>

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.

Jim wrote:
> Jim is answering some of the questions posted:
>
> I want to do it to shorten the braking distance.
>

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


> It is a brand new compact wagon of Japanese unibody design and US
> manufacture. The battery will be inside the rim of the spare tire,
> under the rear floor.
> Everything, including the rear lights, is grounded thru the body - no
> separate ground wires except for a heavy one from the engine block over
> to the battery minus terminal.
>
> The proposed positive cable will be under the car, with heavy duty PVC
> insulation and covered by the black nylon sheathing typically used for
> car wiring. Small sections subject to movement or slight abrasion will
> be inside lengths of rubber hose. I have done this before, and have one
> installation that is now 20 years old with no abrasion problems.
> However, that old vehicle does not have a computer so probably is not
> sensitive to the voltage spikes that occur when you shut off the starter
> motor. Thus, I am interested in dnoyeB's suggestion to run separate
> hot wires to the alternator, computer, and starter. Any idea what gage
> each should be? (Would like to keep the weight down.)
>

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.

> Some posters have identified other cars that have the battery in the
> rear. Does anyone know if they run separate wires for alt, comp,
> starter, or take other precautions?
>
> Jim

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.

>
>
>
> bowgus wrote:
>
>> Well, if I really really needed to remove ... and that's remove, not
>> relocate ... 20 lbs from the front of my jeep, there are smarter
>> "weighs" do it than relocate the frikken battery.
>>
>>
>>


--
Thank you,



"Then said I, Wisdom [is] better than strength: nevertheless the poor
man's wisdom [is] despised, and his words are not heard." Ecclesiastes 9:16

On Sun, 12 Feb 2006, Jim wrote:

> I want to do it to shorten the braking distance.

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.

> The proposed positive cable will be under the car, with heavy duty PVC
> insulation and covered by the black nylon sheathing typically used for
> car wiring. Small sections subject to movement or slight abrasion will
> be inside lengths of rubber hose. I have done this before, and have one
> installation that is now 20 years old with no abrasion problems.
> However, that old vehicle does not have a computer so probably is not
> sensitive to the voltage spikes that occur when you shut off the starter
> motor. Thus, I am interested in dnoyeB's suggestion to run separate hot
> wires to the alternator, computer, and starter. Any idea what gage each
> should be? (Would like to keep the weight down.)

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.

Daniel J. Stern wrote:
> On Sun, 12 Feb 2006, Jim wrote:
>
>> I want to do it to shorten the braking distance.
>
>
> 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.
>
>>
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

Daniel J. Stern wrote:
> On Sun, 12 Feb 2006, Jim wrote:
>
>> I want to do it to shorten the braking distance.
>
>
> 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.
>
>> The proposed positive cable will be under the car, with heavy duty PVC
>> insulation and covered by the black nylon sheathing typically used for
>> car wiring. Small sections subject to movement or slight abrasion
>> will be inside lengths of rubber hose. I have done this before, and
>> have one installation that is now 20 years old with no abrasion
>> problems. However, that old vehicle does not have a computer so
>> probably is not sensitive to the voltage spikes that occur when you
>> shut off the starter motor. Thus, I am interested in dnoyeB's
>> suggestion to run separate hot wires to the alternator, computer, and
>> starter. Any idea what gage each should be? (Would like to keep the
>> weight down.)
>
>
> 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.

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

--
replace "fly" with "com" to reply.
http://home.comcast.net/~njnagel

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:

> Daniel J. Stern wrote:
>
>> On Sun, 12 Feb 2006, Jim wrote:
>>
>>> I want to do it to shorten the braking distance.
>>
>>
>>
>> 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.
>>
>>> The proposed positive cable will be under the car, with heavy duty
>>> PVC insulation and covered by the black nylon sheathing typically
>>> used for car wiring. Small sections subject to movement or slight
>>> abrasion will be inside lengths of rubber hose. I have done this
>>> before, and have one installation that is now 20 years old with no
>>> abrasion problems. However, that old vehicle does not have a
>>> computer so probably is not sensitive to the voltage spikes that
>>> occur when you shut off the starter motor. Thus, I am interested in
>>> dnoyeB's suggestion to run separate hot wires to the alternator,
>>> computer, and starter. Any idea what gage each should be? (Would
>>> like to keep the weight down.)
>>
>>
>>
>> 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.
>
>
> 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
>

Jim wrote:
> 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.
>

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.



> 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
>
>
>


--
Thank you,



"Then said I, Wisdom [is] better than strength: nevertheless the poor
man's wisdom [is] despised, and his words are not heard." Ecclesiastes 9:16

Jim wrote:
> 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.
>

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