Hello, I am working on an electrical system for my 2014 Chevy express extended. I have seen varying opinions on where to terminate the negative cable. Some say to go directly back to the starter battery at the front of the vehicle or a negative terminal under the hood near the starter battery. Others say that it’s OK or even better to find a good spot on the chassis, just sand off the paint and get a good connection and seal it with grease. A Google search said that it’s better to go to the chassis because of the alternators regulator. The alternator and battery management from the vehicle may detect the current coming out for the DC DC charger and give an error message thinking that there’s a problem of power loss somewhere. I guess it kind of confuses the vehicle battery management. Also, obviously it is more length of wire which is more expense and more resistance, and chance for voltage drop. I’m inclined to try just getting a good chassis connection. Any thoughts? Thanks so much!
I assume you are working with an Orion that is non isolated. Meaning it has a single ground terminal. Also, I am assuming you are installing the unit near the house battery bank. In this case I would be fine grounding the Orion directly to chassis. Or ground to your negative battery bus bar that is also sufficiently grounded to chassis depending on how your system is set up. Either way don’t under size the cable and make sure your connections are very good.
Yes, that is correct. We have purchased the Victron Orion XS 12|12-50 DC-DC Charger - Non-Isolated. Thanks for the confirmation! I will definitely appropriately wire size and get a good chassis connection.
And… Yes, I am installing it on a panel board near the house battery and near the wheel well.
btw, I will be installing a shore plug that will have a dedicated AC outlet, as well as powering a victron battery charger. Can the AC ground be connected to the chassis with the dc negative from the dc to dc charger, or to the dc negative bus bar? I seem to get differing perspectives on this. Thanks again!
For your information, the chassis is usually spot-welded, meaning that the actual contact area varies depending on the size of the component. That’s why it makes sense to use appropriately sized wiring—don’t rely on the frame’s ground connection!
I agree with @Karl-Heinz . You need to know whether or not there are good welds between the frame components before relying on the chassis as a suitable negative return path. I don’t allow my installers to cut corners by relying on the chassis for our work. We do bond DC negatives and AC neutral to the frame for a safety “ground”, but I don’t rely on the chassis for a day-to-day return path.
Seriously? I’m pushing back a little here. The frame of the vehicle? The big steel frame? The one that the entire vehicle is built on has unreliable welds? I think you guys are getting a little too picky here. First off, the vast majority of trucks, vans and campers in North America(not sure about other places) are built on frames, not uni body. So you are working with full seam welds on 12-10 gauge steel not spot welded sheet metal. Most campers are built on frames of rectangular steel tubing in the 10 gauge range. The only reason it would be a poor return path is if the connections made are not adequate. In which case, I agree, a return cable would be a better choice. But to say the steel frame is not a suitable conductor is a little far fetched to me.
Just did a little math and 6 AWG stranded copper cable has about 7 times more resistance than 2X3 X 1/8" steel tubing typically used in camper frames. Seems like a decent margin to work within to me and far from “lazy”.
If I am missing something critical let me know.
Here’s my smiley face to indicate I appreciate you guys and this is all friendly and professional. 
Thank you both for your perspective.
Thank you for the bit of pushback. It really helps. - As iron sharpens iron, so we sharpen one another.
Yes, you have to be careful about that these days! For example, some MAN vehicles have frames that are electrically isolated from earth and must remain so!!
Some newer generations of vehicles use special steels or are bonded, which means there is no conductive path.
Poor connections can also cause Bowden cables or metal lines to become unintended conductors (brake lines), with unforeseeable consequences!
Thanks Karl.
Fully welded beams you can get away with it. If anything is bolted together or spot-welded together between two bonding points, no way. I still maintain it’s a lazy way to carry DC negative for anything consuming large currents.
Edit: I’ll add something for posterity. If you have any sort of device that is attached to the frame or body of a vehicle with multiple grounding points, such as a radio transmitter with antenna, ALWAYS run both positive and negative power cables to the battery or main DC buss. This probably doesn’t apply to you, but let’s say you want to install a CB, ham, or LMR radio in a vehicle. The shield of the coax and ground plane of the antenna should be electrically bonded to as much metal as possible and the transmitter itself should have pos & neg cables run to the source. If for some reason the DC negative carrying the high current comes disconnected or opens, upon transmitting the electronics WILL seek a return path and it will be between the tiny electronic traces on the PCB’s via the antenna ground and destroy a potentially expensive piece of electronics. I’m sure others can offer additional examples. FWIW, it’s the same reason Victron says to always connect DC negative first on the inverters before any VE.Bus cables. You don’t want high current seeking a return path through the communication PCBA and VE.Bus cable.
If you’re looking to save some money on cabling by relying on the chassis as your return path then I submit you’re in the wrong business. I don’t mean you specifically, @TherealKT . And this is why I call it lazy wiring. That’s just my installation philosophy.
Thanks, good to know. Another related question; I am installing shore power to my Chevy Express extended van. Trying to find out where to terminate the green ground ac wire. Google says to have an ac panel and connect it to the ground bar, then connect the ground bar to the van chassis and separately connect negative dc bar to the chassis as well. Google also says to not mix the ac ground with the dc negative, so how can that happen if they are both connected to the van chassis, even if at different spots? Thanks.
Actually, I just researched again and Google says to attach the ac ground shore wire to the same chassis spot as the dc negative bus bar (and the negative from an inverter, which I won’t have yet anyway).