Quick grounding question related to battery relocation.

[shadowlurker]

I recently relocated my battery to the trunk, bought some 1 ga welding cable and ran the ground all the way to the front. I plan on grounding to the motor mount shown in the picture. Should i be getting a grounding strap and run that off of the motor mount and to the chassis? And are their any size recommendations/ guidelines i should follow for the strap going to the chassis? Could i get away with something much smaller?

 

[Scooter7M]

Why not run the cable to the stock mounting location on the block, then have a shorter one near the battery to the subframe?

 

[jetjock]

^ This, but to the chassis.

 

[debrucer]

Scooter7M's response sounds like two grounds: one at the stock location, and one near the battery. I thought it was proper to only have one ground.

I purchased a battery relocation kit, and it came with 20 feet of red (positive) wire, and a couple of feet of black (negative) wire. (all 1 ga)

It seems to me that the only wire you need to run from the front to the rear is the positive.

The short black wire will be grounded to the chassis near the battery.

I guess there's nothing wrong with running both wires front to rear; but, it's expensive and I do not think necessary.

Comments? Thanks.

- David

 

[jetjock]

While a single chassis ground near the battery "works" it's not the right way to do things and when done that way the block still needs to be bonded to the chassis lest the starter return current find a destructive way home. The correct way is to provide the starter current a way back while also providing the rest of the system a good ground via the chassis. It's why the car came wired that way, albeit with the battery up front, from the factory.

 

[debrucer]

While a chassis ground near the battery works it's not the right way to do things and when done that way the block still needs to be bonded to the chassis lest the starter return current find a more destructive way home. The correct way is to provide the starter current a way back while also providing the rest of the system a good ground via the chassis. It's why the car came wired that way, albeit with the battery up front, from the factory.

I can smell something melting now

The job at the moment is getting the heater core back in... this is good education. Thanks!

- David

 

[shadowlurker]

Why not run the cable to the stock mounting location on the block, then have a shorter one near the battery to the subframe?

I dont have enough room on the drivers side to fit both the ground and power. So I ran it from the passenger side. I wont have enough welding cable anyhow. So if I mount it in the same place as the picture, then run a cable from that spot to "A" on the tsrm, that would be just as effective correct?
http://www.cygnusx1.net/Supra/Library/TEWD/MK3/manual.aspx?S=Main&P=26

 

[jetjock]

Yep, that'll work. Btw this is also needed by the alternator so there'll be benefits from having it in that respect.

 

[Nick M]

I can smell something melting now


- David

Did you let the magic smoke out?

 

[Scooter7M]

^ This, but to the chassis.

Subrame/ chassis. That what I meant. If you have just the body grounded, keep in mind, the engine, trans, and rear subframe are all mounted with rubber and bolts. Ive done plently of battery relocations and ive always used 2 grounds, a thick postive and a distribution block for the starter and the main relay box.

 

[jetjock]

Directly grounding the subframe is a poor method and by chassis I meant body. The block needs direct grounding to return the starter and alternator current while the body needs it for everything else. Point was you pretty much had it right and for the reasons stated other than the body bonding can be at either end. It's not rocket science, at least not to anyone with even a rudimentary knowledge of electricity.

 

[shadowlurker]

Thanks for the help/replies, I just wanted to double check everything essentially. No point in doing all the work if you're gonna do it wrong.