Negative battery cable/terminal connection

[Ekim7878]

I am working on connecting my harness but I am unclear on what I connect to the negative terminal on the battery.

Do i extend the current negative battery cable from the fuse box to the battery terminal?

[Buzz Skyline]

That's what I did, as well as grounding it to the frame. I also attached as many of the wire harness ground tabs to the frame as I could reasonably manage. No ground issues so far.

[Ekim7878]

Thanks for the response. Did you also extend the positive battery cable from the fuse box and attach it to the battery?

[Buzz Skyline]

I can't recall what I did with the positive connection. I remember running the heavy cable to the starter, but I'm not sure where the other cables connected. I'll take a look when I get home tonight.

[TouchStone]

Thanks for the response. Did you also extend the positive battery cable from the fuse box and attach it to the battery?

That is the best way.

[Frank818]

About grounding the cable to frame, I was wondering, instead of bolting it or something, can we weld the cable onto the frame? Would it make better contact?
Bad ground is too often a problem in electrical wiring, so I wonder what's the best ground we can get with the big negative ground wire from the battery.

[TouchStone]

I'm not sure about welding copper to steel. Maybe brazing or solder, either way a bolt is more than enough. I drilled and tapped directly to the frame then sanded off the power-coat where the lug would contact it.

[Buzz Skyline]

I looked at the wiring in my car. The main cable from the battery goes to the starter, and then some smaller but still heavy gauge wires that bolt to the starter post along with the starter cable go to the main fuse box (the one that used to be under the hood of the WRX) Running them back to the battery instead shouldn't be a problem, but I would make sure they run immediately along side the starter cable in that case. It's always a good idea to avoid making big loops in an electrical system. On the other hand, I doubt there is much to be gained from running all that extra wire.

Welding the ground to the frame would give you a better connection, but I think it would be overkill, and would be a pain if you ever need to disconnect it. As my father-in-law used to say, "perfection is the enemy of good enough."

[GWL]

Use a star washer under the grounding tabs/terminals to bite into the metal frame and tab. Protect against connection corrosion with white lithium or die-electric grease. Dielectric grease is electrically insulating and does not break down when voltage is applied.

George

[TouchStone]

but I would make sure they run immediately along side the starter cable in that case. It's always a good idea to avoid making big loops in an electrical system.

To clarify, big "current" loops should be avoided. Running both positive cables side by side does NOT help with current loops. The idea behind minimizing current loops is to reduce the area between conductors where current is flowing in a complete circuit. Two power cables connected at the battery post wont have electricity flowing between the two since no current loop actually exists.

The best option is to connect your fuse box directly to the battery post, and connect all ground lines to chassis using the shortest wire possible. Car electronics are fairly robust and will work well even if the wiring is not optimal. In both diagrams below the car will run just fine, its to illustrate how current loops occur and a good way to minimize them.
Bad example.pnggood example.png

[Chef818]

I looked at the wiring in my car. The main cable from the battery goes to the starter, and then some smaller but still heavy gauge wires that bolt to the starter post along with the starter cable go to the main fuse box (the one that used to be under the hood of the WRX) Running them back to the battery instead shouldn't be a problem, but I would make sure they run immediately along side the starter cable in that case. It's always a good idea to avoid making big loops in an electrical system. On the other hand, I doubt there is much to be gained from running all that extra wire.

Welding the ground to the frame would give you a better connection, but I think it would be overkill, and would be a pain if you ever need to disconnect it. As my father-in-law used to say, "perfection is the enemy of good enough."

Where on the black fuse box does the red wire connect to?

[mistasherm]

I am at this point with my (donor) wiring harness as well. The harness is in, all connections are made - minus the ones that I still have to lengthen. But I am not as confident as I would like to be with what is going on between the battery, starter, and fuse box(es). The posts on this topic make sense so far and I am a better visual learner, so I will have this pulled up in the garage tonight when I get started. From memory, I have the FFR supplied large gauge, long red wire, some red wire from the donor and a negative terminal "set up" from the donor that has a few ground wires and the battery connection. Thanks for the information so far!

[Hindsight]

I did mine as follows:

Ground post goes right to the frame where I welded on a bolt. Very thick ground wire there, only a foot long.

Battery positive goes to fuse box, and another goes to a starter solenoid on the front firewall. Two positive wires go back from there: one for the starter and the other for the alternator. The big wire for the starter is only hot when the starter solenoid fires. The alternator has a fuse on the wire about a foot from the harness.

[Chef818]

Do you have a pic of where you put the positive to the fuse boxIMG_2444.JPGIMG_2442.JPG

[Hindsight]

Looking at your pic, the black wire with the (yellow?) stripe on it, ending in a ring terminal, with the nut attaching it, is the power wire to connect to the battery.

Here I found one of mine:
http://i.imgur.com/nWxOKf5.jpg

The red wire in my pic, is the same as your black wire with the stripe.
Some of the big white wires that go in there go back to the alternator (it's actually two white wires I believe, that will be side by side). The red wire in my pic (black in yours) goes to the battery.

My ground attachment point:



My starter solenoid (before I loomed the wiring):



Fuse for alternator:



Starter wire through the rear firewall (using a bulkhead electrical post fitting) - The alternator wire goes around the firewall:


You'll likely need to add some large diameter wire to the alternator wires since the alternator is much further away than before (depending on where you put your fusebox). If you do that, it's difficult to splice due to the wires being thick. I used a splice kit that is made of metal, with screws you tighten in on the wire, and it comes with really heavy duty heat shrink with adhesive inner liner that covers it up.

[Chef818]

Got it, thank you. One thing that has been keeping me confused it that the black wire with the yellow stripe is still connected to the negative battery terminal and then from there to the ground that attaches to the bolt on the starter / tranny. and the black wire with the red strip (in the second pic) has the positive battery terminal and the connector that I can't remember where it goes. It seems like it want's to go on the same nut / screw that the black with yellow strip is, but you wouldn't put a positive and negative on the same connector?

[Hindsight]

A lot of that sounds backwards to me.... do you have a wiring diagram for your donor car? What year is it?

[Chef818]

yes to wiring diagram and it's a 2003. using the one below
http://ken-gilbert.com/wrx/mans/7%20-%20WIRING.PDF

[Hindsight]

The thick wire in the first pic is definitely the battery power wire, and should go to battery positive. Sounds like it's routed incorrectly. The wire in the second pic could either go directly to the fusebox (in place of the wire in the first pic), or that could have gone to something else.... tough to say, but I think it probably goes to the fusebox where that nut is.

All this is from my 2007... so it might be different, but I don't think the fusebox is going to have a big ground wire going to it in any year. Just no need for a big one.