Battery Relocation

[msprince]

Im sticking my Battery in my boot to make way for a custom air intake kit.

I think 4awg is good for the job as my mate has the same in his evo and his is fine.

Im getting five meters in red and five in black.

Just asking for opinions:

Do people think it will be ok?

[dangermooser]

I have seen a few people do this so should be fine, must admit I am quite tempted to do it myself

[mr-p]

yeah is a good idea think it will make the engine bay look better to where you going to mount it?

[Jamesbelfast]

Just remember that in the event of an accident and the Battery fractures acid may be spilled into the interior of the car - not good for your skin.

What happens to the gases vented from the Battery is another consideration.

Sealed Battery casing or capsules are avalilable for caravans.

No need to run two cables either - a short earthing strap to the nearest metal part of the bodywork should suffice.

Also are there lilely to be any insurance complications - it may be worth asking.

[nrgizerbunny]

I would run two cables. The positive is for obvious reasons.

The earth is due to the body having a resistance, you might get a strange floating ground issue which is just a few mV higher than true ground. This would screw your engine sensors up and you might end up with a car running rich or poor idle etc until the thing learns

[msprince]

Cheers james thought about that.

Im looking at sealed Battery boxes.

Im think of mounting it in the top left or right corner, just cut a rectangle out of the floor carpet in the boot.

Yeah deff running two cables.

[Karma Supra]

Battery acid is nastry stuff... I had one in the boot of one of my supras (getting it back off a mate that "borrowed" it).

Some dopey cow in an Espace pulled out infront of me without looking causing me to carry out an emergency stop.. the Battery rolled over in the boot and leaked slightly...

It burnt right through the carpet and made a mess of the metal on the boot floor! the "dark" supra carpets were !Removed! rare and I never managed to replace it either :(

[msprince]

Yeah its not nice stuff.

Im making sure its really secure.

[Jamesbelfast]

I would run two cables. The positive is for obvious reasons.

The earth is due to the body having a resistance, you might get a strange floating ground issue which is just a few mV higher than true ground. This would screw your engine sensors up and you might end up with a car running rich or poor idle etc until the thing learns

Running two cables runs the risk of higher resistance especially when under heavy load during engine start-up- a few simple tests with a decent multi-meter would soon test the earths.

Also if fitting a Battery box remember it will have to be vented to outside the cabin area.

In order to comply with insurance the cables may need to be protected depending on how they are routed.

[nrgizerbunny]

I would run two cables. The positive is for obvious reasons.

The earth is due to the body having a resistance, you might get a strange floating ground issue which is just a few mV higher than true ground. This would screw your engine sensors up and you might end up with a car running rich or poor idle etc until the thing learns

Running two cables runs the risk of higher resistance especially when under heavy load during engine start-up- a few simple tests with a decent multi-meter would soon test the earths.

Also if fitting a Battery box remember it will have to be vented to outside the cabin area.

In order to comply with insurance the cables may need to be protected depending on how they are routed.

what a load of drivel.

Let me illustrate with an example. The O2 sensor on the car requires a signal that oscillates around 0.45V which is small. You move your Battery from the current position to the rear of the car, the resistance is now each body panel plus the spot welds to get to the back, hence instead of it reading 0.45V it might read 0.49V which would be enough to cause it to dump more fuel in and screw up the economy of your car.

My next point is the resistance of thick cable will be less than that of body panels and finally your grounding point has now changed, instead of having a ground point on the engine block you will be reliant on the body for grounding - this is a bad idea, there is nothing on a car that is high load that is not grounded directly or very close to the Battery. The starter, alternator and even air pump are grounded very closely to the battery.

[Jamesbelfast]

I would run two cables. The positive is for obvious reasons.

The earth is due to the body having a resistance, you might get a strange floating ground issue which is just a few mV higher than true ground. This would screw your engine sensors up and you might end up with a car running rich or poor idle etc until the thing learns

Running two cables runs the risk of higher resistance especially when under heavy load during engine start-up- a few simple tests with a decent multi-meter would soon test the earths.

Also if fitting a Battery box remember it will have to be vented to outside the cabin area.

In order to comply with insurance the cables may need to be protected depending on how they are routed.

what a load of drivel.

Let me illustrate with an example. The O2 sensor on the car requires a signal that oscillates around 0.45V which is small. You move your Battery from the current position to the rear of the car, the resistance is now each body panel plus the spot welds to get to the back, hence instead of it reading 0.45V it might read 0.49V which would be enough to cause it to dump more fuel in and screw up the economy of your car.

My next point is the resistance of thick cable will be less than that of body panels and finally your grounding point has now changed, instead of having a ground point on the engine block you will be reliant on the body for grounding - this is a bad idea, there is nothing on a car that is high load that is not grounded directly or very close to the Battery. The starter, alternator and even air pump are grounded very closely to the battery.

You may well be right but without knowing the resistance values of the car body how could you compare.

My neighbour fits high-tec electronic equipment to both cars and trucks and using his top of the range Fluke multi-meter he can't find any significant difference between the back of a car and the front when it comes to bodywork earthing.

Do you happen to know the earthing capabilities of the bdoywork for comparison - would be a great help to other members if they are considering resiting their battery.

[mr-p]

i think the size of the cabling is the most important factor not where the ground is, not to mention the extra length needed in the wiring which could mess with the resistance's

a longer cable will mean higher resistance if it is not the right gauge for the extra length because the power has to flow through more cable so you would need thicker gauge wiring to compensate for the extra length to keep the resistance close to what it should be and using to big gauge cable will result in lower resistances

[nrgizerbunny]

I have a car PC in my car and that has it's power and ground taken directly from the Battery, if it is grounded anywhere else I get horrendous interference on the radio.

This is slightly different to the OP's question as my problem is high frequency electronics not power delivery.

As Mr P has said, If you are extending the cable, you need to make it thicker for the extra resistance. there are some guides on electrical resistance versus cross sectional area by googling.

[mr-p]

I have a car PC in my car and that has it's power and ground taken directly from the battery, if it is grounded anywhere else I get horrendous interference on the radio.

This is slightly different to the OP's question as my problem is high frequency electronics not power delivery.

As Mr P has said, If you are extending the cable, you need to make it thicker for the extra resistance. there are some guides on electrical resistance versus cross sectional area by googling.

having a poor earth for the pc would be horrendous just the same as sound systems if you have the wrong earth or a poor earth you get interference through the Speakers

[Cyker]

Battery acid is nastry stuff... I had one in the boot of one of my supras (getting it back off a mate that "borrowed" it).

Some dopey cow in an Espace pulled out infront of me without looking causing me to carry out an emergency stop.. the battery rolled over in the boot and leaked slightly...

It burnt right through the carpet and made a mess of the metal on the boot floor! the "dark" supra carpets were !Removed! rare and I never managed to replace it either :(

This is why sealed gel-packs rock

[ae111sr]

Don't forget to fuse the live cable as close to the Battery as possible. This is similar to the the one I used RS Components it fits onto the Battery terminal. I'm using 125 amp fuses.