DIY: Battery Relo

wstar

We'll find out tomorrow if the 200A breaker works.

As for the grounding issues, I don't see any point in running a separate ground wire along the length of the car. The car's body itself should provide more ground path than any reasonable wire could hope to.

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miguez

Agreed. FricFrac, can you add any info tho why you'd recommend that?

wstar

Installed the breaker this evening. The car started fine without tripping it. Then again, it's a hot summer-ish evening and the car had only been off for 5 hours. Might be different on an ice cold morning in the dead of winter with a car that hasn't been run in 2 days. We'll see when I get there in the winter

I also went ahead and prewired a little harness for my trickle charger in case I need/decide to use it. The breaker is mounted to the top of the battery box with superglue (I know, how ghetto of me).

But anyways, yes, the Lightning Audio LCB-200 seems to do the trick, providing short-circuit protection as well as a convenient way to kill the battery power when working on the car.

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FricFrac

The conduction of steel is poor compared to copper. Typically copper is used as the baseline as its is the most common and almost best conductor (wow that english sucked but carry on...). Copper is only surpassed by silver for conductivity at about 106% as conductive as copper. Steel for the record sucks hard at electrical conduction ranging from 2 to 18% for pure steel in comparision to copper. I'd expect our sheet metal to be somewhere around 12% ish.

One of the main issues you are going to have with a vehicle electrically is a good path to your power. Grounding to the chasis is good enough for most applications but when you start involving multi sensors and multi computer controlled systems to your vehicle small glitches in signals and poor grounds can cause problems. IIRC Stillen makes a grounding kit for the car computers because of this very issue. In the olden days if you got 14.4V to the coil or 14.3V who cares - its not gonna make a difference but if a signal gets lost and isn't part of a calculation you carputer need to make a decision you aren't going to perform optimally. That's just voltage I'm not even getting into eddy currents, etc. The car is a horribly noisy environment electronically which is why the basics are so important.

The other issue is your connection to the chassis. Once that iron starts to oxidize you are adding resistance which means power loss. Don't forget that bitty screw in the sheet metal is the best contact point to the steel but you've probably got three or four dissimillar metals there. Dissimmilar metals cause corrosion as well. Although you've got huge surface area in the sheet metal your contact point basically negates its huge current carrying capability. In real life these are minor points but in racing most of us want to know the little details and determine whether they are worth addressing or not.

So in short (oh didn't plan that pun...) your set up will work but we are pit racing here so if you wanna squeeze every last drop or optimize your system that's why I'd recomend running a ground line. At the very least I'd run ground wires from the carputers directly to the battery because they are the most likely to suffer ill effects but that's just me....

wstar

I'm well aware that I have several junctions of dissimilar metals, but I don't plan to let anything corrode significantly. That's why all those joints got coated in anti-oxidant, and why I'll be checking and cleaning them on a regular basis.

And while mild steel may have roughly one tenth the conductivity of copper, there's still a lot of it between the battery and the various sensors and computers you're talking about. It really just comes down to the junction points, and they're sufficient in size for the amperages involved (think about it this way, 1/10th the surface area of that lug screwed into the trunk is still more than enough width of copper for the current involved).

As for the Stillen grounding kit, its primary function is to help ground the engine block to the body. I have it installed in my car. One end does go to the negative battery terminal as well (or did, before I pulled the battery), but clearly its primary purpose is to ensure a good engine-to-body ground, so that a potential difference doesn't develop between the two.

I'm not saying you don't have a point about the cleanliness and stability of the ground reference in the car, but I think you're being overly paranoid about it. If you'd like, I could go measure the resistance of the car body from the current battery ground point to the old one up front for you, and we can compare that to the known resistance of my 15 ft run of 1/0 copper for the positive side, if that provides any insight. I don't think there will be a difference worth caring about.

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