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Discussion Starter · #1 ·
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Battery bank is in the back passenger side. Where is the best/safest place to ground the electrical system?

Seen some advise using this larger bolt hole above the wheel well.

Thanks
 

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I'm about to start hooking up my electronics in the next few days in the same area. I think there is a little gray cover to the right of the wheel well that has some grounding points behind it? I was assuming we could use those? (Basically right behind the bottom of your multiplus). I'd wait for someone else to chime in though, I'm not sure that I'm correct.
 

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Discussion Starter · #4 ·
Yeah I was thinking that area as well. But I read in other posts that the sheet metal is too thin in that area to handle the amps of a system like this.
 

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I personally prefer to run a ground cable. If you want to use the body, make sure that you can access it after your build. Do a proper hydraulic crimp, no impact type. Make sure to clean all paint and make sure the lug is making flat connection to the metal. Paint or otherwise protect the connection to help prevent corrosion. I agree that the sheet metal with the 3 connections in the rear is too little for a power system. The places where the tie down loops go have been used with success.
 

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So a poor ground can kill your electronics faster than a diet of cheeseburger and fries!
The ground points under that little grey cover are probably not adequate for your job.
Best to use a ground cable or look around for a factory threaded bolt that’s about 5/8”.
Probably above your rear tire might be behind one of your batteries.
 

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This has been discussed a lot on the forum so best to search the topic. There are different schools of thought on the best ground location. Here is one good discussion:
 

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As @Rigel says, many threads on this. Until 2020, the correct ground point is anywhere there is a solid ground option available - including the battery. Though little changed in the electrical system, the Ford "recommended" ground points became a big topic. Plenty of threads and a lot of, "I've done this for years and it's always worked," and plenty of, "anything not clearly listed in the Ford official BEMM will likely burn your van to the ground."

The most relevant bit in all the banter is that there is a chart that lists what the 20+ listed ground points power capacity is. Sadly, they're listed something like, "small or large," leaving it rather useless; but proving that using an "approved" ground point that should only be applicable to a 12-gauge wire is NOT the correct place to terminate a 4/0 cable.

You show 200Ah of 12VDC batteries (assuming parallel since the inverter is a 12VDC unit) and a 2kW inverter. But those don't /need/ to be connected to the van ground system - they can be, "floating," as well - meaning all grounds for the house system are isolated from the van but travel back to the negative of those batteries (to a buss bar, typically).

So the correct question is, "what is the ground intended for?" If it's for a DC-DC that is pulling from the alternator / battery, then the max draw of that system is your relevant info. If it's the ground loop for all things house-powered, then it's a question of how you wire those and the max load there. But the good news is that the ~150-200A that you need to flow between the batteries and the inverter need not go through that ground - so it doesn't need to be 4/0. (Though the cables from the inverter to the batteries likely need to be in the 2/0 range.)

Something else to take into account: as listed on the batteries, their sustained current is ~100A; two of them together is adequate for the inverter, but one would not be; and two is just barely enough - three would be better.


Oh... and if you DO want/need a 200A ground in the back of the van, use the d-ring bolt right behind your batteries. There's posts on how to do that here: grind off paint, etc.
 

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So you’re saying you prefer to run a ground cable to where?
Well, I run a ground line to everything. I have seen too many bad chassis grounds. Chassis grounds can go bad from moisture or vibration or because they weren't done right in the first place. Not all places in a unibody like the Transit are properly bonded. And if they are buried, how do you get to them without tearing things up? I don't care that the chassis is technically a larger wire. I can size the wire to have an acceptable voltage drop.

Now, there are many chassis grounds working just fine out there. So do what makes sense to you. As I said before I would make sure that you can get to it and that it is done right. The BEMM has the blessed Ford spots but there are other places that will work just fine.
 
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I never had any success until I ran a ground cable to the ground point between the seats next to the E-brake.

I tried others at the back to no good effect.
 

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Before 2020 there were no ground points shown in the Bemm, So it was simple and very few people asked about where to ground. Now thanks to the newer Bemm everybody is confused.
 

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Look for a threaded bolt hole around the top of the wheel well. I used this but I have a 350 passenger hd wagon so not sure if its there for yours. Regardless, you want to strip the paint to bare metal.
 

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Discussion Starter · #18 ·
Well, I run a ground line to everything. I have seen too many bad chassis grounds. Chassis grounds can go bad from moisture or vibration or because they weren't done right in the first place. Not all places in a unibody like the Transit are properly bonded. And if they are buried, how do you get to them without tearing things up? I don't care that the chassis is technically a larger wire. I can size the wire to have an acceptable voltage drop.

Now, there are many chassis grounds working just fine out there. So do what makes sense to you. As I said before I would make sure that you can get to it and that it is done right. The BEMM has the blessed Ford spots but there are other places that will work just fine.
So I think we are speaking the same language. But can you confirm this is what you mean. I was going to ground my entire electrical system by running a cable from the negative bus bar to the chassis. Probably to the bolt hole above the wheel well.
 

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So I think we are speaking the same language. But can you confirm this is what you mean. I was going to ground my entire electrical system by running a cable from the negative bus bar to the chassis. Probably to the bolt hole above the wheel well.
So I take it you mean that with your DC to DC converter to charge the house batteries (for a high current example) that you will run two wires? An that you want to connect the negative side of your batteries to the chassis to form a ground? Yes, you can do that. You can also float the inverter/charger side of the DC house system. If you want to go down a rabbit hole there is much disagreement on whether or not you should ground your system like that. And then if you are a radio nut like me, a whole new debate opens up.
 
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