Rear battery ground?

[Simmie]

I'm in the middle of converting my '89 320i to a rear battery set-up. However, I think i'm missing the block that is used to ground the battery.

Here's a picture of my battery tray



And here's a picture I found on Google of what I think i'm missing



How do I ground the battery

[george graves]

I'm surprised there isn't on from the factory - so you'll have to make your own. Grind away paint and then install a lug. Cover with paint of any part that is exposed.

[Simmie]

I'm surprised there isn't on from the factory - so you'll have to make your own. Grind away paint and then install a lug. Cover with paint of any part that is exposed.

Do you think I could make a ground out of the marked area?



Seems like it would be the easiest way.

[george graves]

You can make a ground anywhere.

[jeffnhiscars]

that looks like the fuel filler door. Not the place to run a direct to battery ground

[george graves]

Sigh. That's not a fuel filler door.

[e30s50dan]

If you can,just weld a bot to the chassis

[Simmie]

Forgot to update with my success.

I just ground the paint off using a dremel.



And found a bolt + washers to stick the ground on.



Works great

[george graves]

It's a bracket. I would go with actual body metal if it was me. Turn on your HVAC fan, head lights, AC and run your windows up and down. If your lights dim, or that bracket even gets warm, it's a clear sign it's a bad idea. Well, heck - it's a bad idea, but that a test to see how bad it is. No offence - it may work fine - it's just not 100% proper, if you know what I mean.

[AndrewBird]

I'd remove the bumper, drill a hole in the same spot as the factory and put a stainless bolt through from the outside with a nut on the inside. Put a large washer on each side as well and don't forget to remove some paint. Then put the battery cable on with another nut to hold it. Spray over the bolt on the outside with undercoating or bedliner to seal it up.

[AndrewBird]

Either that, or you could use one of these:

https://www.mcmaster.com/#rivet-nuts/=1b86kvl

[george graves]

Rivet nuts are the best! Also called "nut-serts".

Not sure I would go with stainless. Then you're just creating a galvanic sandwich.

[AndrewBird]

I suppose that's true about the stainless. I was just thinking to help fight rust.

[george graves]

There's more than one type of stainless. All need air(oxygen) to remain "stainless" as I understand them. It's a weird medal for sure. Not what you think it is.

[SpartanE30]

How much cable did you use to run the power from the engine bay? I plan on doing the same conversion. I have to clean out trunk though first.