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2020 350 HR CARGO AWD 148" 3.5 ECOBOOST
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Discussion Starter · #1 ·
There is a lot of dispersed info on the forum on grounding and I've looked at a lot of it. I wanted to ask a question, just start a discussion to collect/consolidate the community knowledge, advice and experience. My specific interest and the decision I need to make is high power grounding specifically for an inverter connected to CCP2 175A point that many of us have. (2020 350 cargo, dual batt, upfitter pkg) Don't have the detailed design, but max would be a 2000W inverter which would be pretty much on (or over) the edge for the chassis fusing for the CPP2. More likely smaller (like 1000W)depending on what I find and design, and need.
I've got and "studied" the BEMM. I understand the basic surface area, resistance, (over) heating concepts. So I've got 3 main ideas right now. GP #25 in the floor; seems kind of small, already a pile of stuff on there, a sheet metal ground(?). And from forum info; e-brake bracket (Orton), and tiedown ring bolt (behind driver seat). Seems direct to battery neg. is no-no from BEMM, bypasses battery protection and probably lots of other controls. Anyhow I'd like to focus on good/possible ground points for the 2000W max option. Look forward to hearing what has been done and why. Thx
 

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2020 High-Extended AWD EcoBoost Cargo with windows
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Looks like you've covered the breadth. And you're clear on the official / non-official (though it has been suggested that "official" might have been different on the older rigs, such as when Orton built his).
 

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A recent Ground Point thread with Bemm quotes from me and others, Scroll down.

I have been using a D-ring bolt hole above the rear wheelwell for five years now without problems, Granted I am only using a 60 amp battery to battery charger on this chassis ground.

 

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2020 350 HR CARGO AWD 148" 3.5 ECOBOOST
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Discussion Starter · #4 ·
With the high current CCPs it seems kinda stooopid for Ford not to have put in an obvious commensurate ground point (even for older rigs). Instead I have to sand off some paint somewhere and hope that I've got good continuity through to the chassis etc. MO, are you just depending on the threads and the weld nut contact or did you sand a bit to bare metal?

I kinda like the e-brake location but everything looks to be nicely painted and I wonder about the path I cannot see. I'm sure the metal pieces were all painted before assembly so the only good conductive path is likely through the nut/bolt thread area there too. With that kind of current I'd rather not be guessing.

I do find a hole through the floor just between the seats abit aft and left of GP 25 covered with a silly clear stick on plastic bandaid. Thinking to feed some good sized cable down there find a frame bolt ( there seem to be several) and build a confirmed high current ground.
 

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2020 350 HR CARGO AWD 148" 3.5 ECOBOOST
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Discussion Starter · #5 ·
Sorry, really a frame bolt location somewhere underneath...

Vis the referenced thread: I had read that and just looked back, got to be more about divining the intent of the BEMM. Seems that is full of what not to do vs what to do, sounds like lawyers. I'd like to hear what professional upfitters do. There is a lot of serious equipment run off of these platforms and they are not grounding to little bolts in the floor of the van.
 

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With the high current CCPs it seems kinda stooopid for Ford not to have put in an obvious commensurate ground point (even for older rigs). ...
Yes, it would make all our lives easier if they just had a "CCP Ground bolt" right there for us (y)
I do find a hole through the floor just between the seats abit aft and left of GP 25 covered with a silly clear stick on plastic bandaid.
It appears that hole is for a threaded Torx stud for the vans that have the new molded plastic plate there. It may have a welded captive nut under it that could be helpful.
PS: Still waiting for a new van owner to let us know what that panel is for... :rolleyes:
 

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I've been doing a lot of reading on this topic lately as well. I found this article to be very informative, even though the discussion is tied to starter batteries, not house batteries. It also references another article by the same author which was also interesting. I think what has us all spooked is that Ford uses really small studs/bolts (6mm or less?) for the ground connections, and we are equating the size of the stud with the capacity of the ground.

Read the entire article, but this snippet in the yellow box is very relevant:
A four foot wide area of floor pan, just .06 inches in thickness, would have a cross section of about 2.88 square inches. The equivalent copper conductor would have to be 2.88/8.8 = .327 square inches, or a diameter = 2* sqrt of A/pi, or .645 inches diameter! Equaling the resistance of a thin 4-foot wide steel floor pan with a copper cable requires a cable larger than 4/0 , and we have not even counted the help from frame rails, rocker panels, or roof paths!
 

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... I think what has us all spooked is that Ford uses really small studs/bolts (6mm or less?) for the ground connections, and we are equating the size of the stud with the capacity of the ground.
...
At least for me, part of the concern is using the correct wire gauge for the load while getting /TO/ the ground bolt.

FWIW, I'm not surprised that most body points are probably adequate grounds. The car-audio folks have been running massive power at 12V for many years that way. But should we have a small connector on a sizeable cable because that's the easiest way to get to the (Ford approved) ground point?

Someone here had a post about aircraft standards for wiring being, "if the wire isn't hot you used too large a gauge," or something like that. :oops:😁 But it has stuck with me to remind me that the issue is how much resistance / voltage loss and/or heat-rise we find acceptable. It seems we van-building amateurs lean toward over-spec in many cases (I often do); but the aircraft example is an interesting one. I had a case in the last rig where I under-sized... and the voltage drop on load caused the fridge to shut off (thankfully nothing worse) so I've leaned toward over-sizing cables since.

Depending how much constant draw one might encounter on CCP2 and CCP1, I think matching the ground cable (and ground point) appropriately makes sense. Max constant draw is in the ~150A-ish and ~50A-ish for both on a 2020. A 200A constant load (if one were actually pushing them) could be a sizeable cable - depending on one's choices. I ran 2/0 as the common ground for both. Overkill, I'm sure. I ran 1/0 for the CCP2 load (I am hitting it at ~120A+ constant) and #4 (IIRC) for CCP (not likely to use that, but maybe?) and 2/0 seemed like appropriately matched over-kill. But I'm not sure I'd have run that to ground point #25... 🤔

All that to say really... Ford should have put a 200A sized ground BOLT (something suitable to #4 gauge wire at least, if not #2 or 1/0) next to the CCP points. (Oh... or you could say they did. ;) )
 

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@gregoryx, agree with your sentiments. It is weird that Ford does not put at least two nice-sized ground studs in the van, one next to CCP and another in the rear.

With dual alternators, I'm planning to at least attempt to run 200A constant with a direct connect to the battery positive and load shedding, in spite of the BEMM saying 120A constant. And I'm planning to use a 4/0 chassis ground, due to a combination of using a Victron MultiPlus 3000, their recommended 4/0 cabling (2/0 min) from house batteries, and ABYC chassis grounding recommended to be equal to size of DC+. Still deciding on grounding point.

We'll see how reality matches the plan.
 

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I'm no electrical engineer, can someone shed some light on why the diameter of the ground bolt matters?
What matters is the surface area available for the flow of electrons. A small surface area will create more resistance to flow (think a pinched hose). This resistance causes a voltage drop and depending on the amperage, heat. Too much of either can create understandably poor outcomes.
 

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...
With dual alternators, I'm planning to at least attempt to run 200A constant with a direct connect to the battery positive and load shedding, in spite of the BEMM saying 120A constant. And I'm planning to use a 4/0 chassis ground, due to a combination of using a Victron MultiPlus 3000, their recommended 4/0 cabling (2/0 min) from house batteries, and ABYC chassis grounding recommended to be equal to size of DC+. Still deciding on grounding point.
...
I moved from 12V house in the last rig to 24V house in the new rig as the power storage and loads grew. I have the Multiplus 3k as well (on the house batteries) but at 24V, that's a more tolerable amperage load. But the truck side... I mean... it's as much load as my house situation but for half the power. 🤷‍♀️

I'm no electrical engineer, can someone shed some light on why the diameter of the ground bolt matters?
@asdrew , I'm no electrical engineer either; but the gauge of the wire matters; and which ends can be crimped/soldered on them matters, so the size / accessibility of the bolt matters - at least to that extent. But I can't think of anything stopping it from being very small... so long as the contact areas between the metal /below/ the bolt and the connector touching it are large / good. But those two don't usually go together...
 

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With dual alternators, I'm planning to at least attempt to run 200A constant with a direct connect to the battery positive and load shedding, in spite of the BEMM saying 120A constant. And I'm planning to use a 4/0 chassis ground, due to a combination of using a Victron MultiPlus 3000, their recommended 4/0 cabling (2/0 min) from house batteries, and ABYC chassis grounding recommended to be equal to size of DC+. Still deciding on grounding point.

We'll see how reality matches the plan.
Can you share how you plan to implement load shedding, and how it can be tested with a high load? Thank you.
 

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For my alternator-powered 2kW inverter, I directly connected to the starter battery negative post with 2/0 cable inside 3/4" split loom, thru a 1" hole in seat base.



That's how this retired electrical engineer did his. I only trust the high-current ground connections Ford already uses to connect alternator to batteries. This was the most accessible of those connections for me.

On the positive side, I connected to the alternator side of the 470A fuse with this modification to allow a second 2/0 cable lug upside down under alt cable lug.



Then routed out like the negative cable. A 300A fuse is at the other end of this positive cable.



Good luck with your wiring!

Catfish ...
 

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@asdrew , I'm no electrical engineer either; but the gauge of the wire matters; and which ends can be crimped/soldered on them matters, so the size / accessibility of the bolt matters - at least to that extent.
What matters is the surface area available for the flow of electrons.
As another paid up member of the not-an-electrical-engineer club...isn't the question a combination of bolt size and depth of contact to know the surface area? For a 4 mm diameter bolt (so not very big, about 1/6 inch) that contacts in 3 mm depth (total guess)...is that not about 38 mm sq. of contact surface area? Or almost the cross sectional area of 1AWG wire?
 

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...

That's how this retired electrical engineer did his. I only trust the high-current ground connections Ford already uses to connect alternator to batteries.

...

Good luck with your wiring!

Catfish ...
Very nicely done. Good to know /someone/ here is officially certifiable at something! 😄


As another paid up member of the not-an-electrical-engineer club...isn't the question a combination of bolt size and depth of contact to know the surface area? For a 4 mm diameter bolt (so not very big, about 1/6 inch) that contacts in 3 mm depth (total guess)...is that not about 38 mm sq. of contact surface area? Or almost the cross sectional area of 1AWG wire?
I have used various end-connectors for up to 4/0 (all attached with the hydraulic crimp tool) that have various sized holes for the bolts. I think the smallest bolt-size I've used for 4/0 might have been 5/16" - about 8mm - but the width of the end-connector was/is in the 3/4" or larger size. I've attached those to battery terminals and to bus-bar setups. In those cases, even a smaller bolt would've been fine - the big surface-area thing would probably still be happening. IOW, I don't think of the bolt-size having anything to do with the electrical transmission - it's on the contact of the two surfaces and the bolt holds them together.

But a big bolt does seem to hold all that together quite well.... 🤔


Back to @NEvanVenture - you finally got a response from an ACTUAL electrical engineer above! Don't mind the rest of us. We do this to /every/ thread... regardless of what the original poster wanted. :rolleyes: 🤣
 

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As another paid up member of the not-an-electrical-engineer club...isn't the question a combination of bolt size and depth of contact to know the surface area? For a 4 mm diameter bolt (so not very big, about 1/6 inch) that contacts in 3 mm depth (total guess)...is that not about 38 mm sq. of contact surface area? Or almost the cross sectional area of 1AWG wire?
I drew a quick picture. The key point is that the bolt isn't the primary path for current flow. The benefit of a large bolt is that you can achieve high compression (force) between a lug and the van metal.It is assumed that paint or non-conducting materials are removed from the van body where this compression occurs. The majority of current flows as shown in green. Depending on how the nut is contacted, i.e. welded to body etc., it can contribute to lowering the overall resistance but provides much less surface area than the washer/lug/body interface and is a longer electrical path, thus it is not a primary path.
151001
 
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