I have a cargo trailer I have just installed a 12 V solar system in. The trailer's rear lights come on with the car's battery. Like the car, the trailer's chassis uses the negative ground of the car for it's tail lights. Can I ground negative cable of the trailer battery to the trailer's chassis also? Or would this cause issues with the 2 batteries?
Grounding Negative of Trailer Battery to the Chassis
- Thread starter DavidD
- Start date
Vigo
Solar Addict
So you're right that the negative of both the tow vehicle battery, and the trailer battery, are connected once you plug in the trailer connector. However, there is no path between the positives of the two batteries, so nothing occurs between them.
In my RV i have both my lifepo4 and lead acid batteries grounded to the chassis. But, because there is no connection between the positive sides of the two circuits, nothing happens.
In my RV i have both my lifepo4 and lead acid batteries grounded to the chassis. But, because there is no connection between the positive sides of the two circuits, nothing happens.
Vigo
Solar Addict
No, but deciding not to use chassis grounds mean you will have to run a dedicated ground wire all the way back on every circuit. Generally with vehicles using chassis grounding seriously reduces the amount of copper required to wire the thing, BUT if you are only adding a few circuits and don't mind the additional wiring, it is fine to do what you're saying.
gardengunguy
New Member
I need to ground my 12v system to my cargo trailer chassis. Can I wire this to the frame in my wall, or would it be better to go through the floor and ground it underneath? I have my system in a 2x4 ft bench and using a Lynx Distributor for my busbars. I'm debating whether to cut a hole in my wall to go through to the solar box, or to go through the floor and attach it underneath. Is there a safety of fire concern being ground behind the box in the wall? Thanks...
Either way is fine as long as the wall frame has a good place to connect. No special fire hazard to connect.
Vigo
Solar Addict
It depends on.. everything, but would usually be fine. It depends on current, and what the material is, how much of it there is (in terms of like cross sectional area) and whether theres something worse in between where you start and where youre going. Like, if you attach to a 1” steel square tube you know what that is but you dont really know if at the bottom it joins the next piece with only two welds that go halfway across two sides. That would be 1/4 the cross sectional area if we’re winging it, a ‘bottleneck’.
Ive heard approximations that steel is like 14-30x worse as a conductor than copper. So if for example youre looking at a wall spar or stud abd imagine it as a piece of copper 1/15th the size, you might get a rough idea. Vehicle framerails are usually big enough that a piece of copper 1/15th the size is still a big piece of wire, but once you get up into the body structure thats not generally true and you have to think about whats in between. For example, if you screw down to a truck cab or bed thats suspended on bushings, you have nowhere near as much ‘conductor’ between the body and frame as what you think. For example, A newer tahoe i believe has a battery that grounds to the firewall which means the cab itself has a fullsize ground wire which grounds it to the frame. You can ground anything to that body because the ground path is designed for hundreds of amps from the starter motor. An older chevy truck might have a battery negative that makes a pit stop on the frame before continuing to the engine block but only a 10 gauge wire goes to the fender/body. So, it depends.
If youre talking really low currents, itll almost always be fine. Big currents, you gotta be picky.
Ive heard approximations that steel is like 14-30x worse as a conductor than copper. So if for example youre looking at a wall spar or stud abd imagine it as a piece of copper 1/15th the size, you might get a rough idea. Vehicle framerails are usually big enough that a piece of copper 1/15th the size is still a big piece of wire, but once you get up into the body structure thats not generally true and you have to think about whats in between. For example, if you screw down to a truck cab or bed thats suspended on bushings, you have nowhere near as much ‘conductor’ between the body and frame as what you think. For example, A newer tahoe i believe has a battery that grounds to the firewall which means the cab itself has a fullsize ground wire which grounds it to the frame. You can ground anything to that body because the ground path is designed for hundreds of amps from the starter motor. An older chevy truck might have a battery negative that makes a pit stop on the frame before continuing to the engine block but only a 10 gauge wire goes to the fender/body. So, it depends.
If youre talking really low currents, itll almost always be fine. Big currents, you gotta be picky.
Last edited:
gardengunguy
New Member
Thank you, I wound up going through the floor and grounding it to the frame. I've watched so many YouTube videos and I've seen people do both, and I've seen a lot of wrong ways too. I probably should've started a new thread but I came across this one first. Thanks again..
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