Electrical grounding question

[Greyfox]

Hey everyone,

So I'm in the process of building my overland trailer. I'm custom designing a large tool box for my electrical set up. Below is a brief description of what its including(I have some of the equipment not all)

m1102 trailer, custom rack, 23zero rtt


2x 100ah deep cycle batteries
blue sea safety hub 150
redarc 1240dc charger
victron pure sine inverter
victron battery monitor
the rest is basics battery (battery switch, couple circuit breakers, etc)

As far as all the wiring goes I don't have any major issues I can handle that stuff.

Where I have a slight question is with the grounding. I normally have a common or earth ground would be the frame of a car or whatnot. I'm just not sure when it comes to the making in the toolbox. can I just mount a grounding plate to the tool box? do I need to ground the toolbox to the trailer itself?

Thank you guys for any help

 

[grubworm]

I normally have a common or earth ground would be the frame of a car or whatnot. I'm just not sure when it comes to the making in the toolbox. can I just mount a grounding plate to the tool box? do I need to ground the toolbox to the trailer itself?

"common" and "earth ground" are two different things and are used in alternating current. common is the white wire in your circuit panel also called the neutral conductor and references zero potential whereas the earth ground is a copper rod stuck in the ground and connected to the circuit panel and connects to the bare copper wire you see in outlet boxes. its intended to be a path of least resistance in case of a short so that a person touching the shorted device is not completing the circuit and getting shocked.
for your trailer and using direct current, you will have either a chassis ground where the frame completes the circuit, or a floating ground, where the ground (negative wire) goes directly between the battery and the load, or the between the load and a bus bar.

expecting to have a lot of vibration and exposure to moisture, i would use a bus bar for my ground versus a chassis ground. take a larger gauge wire and run it from your negative terminal to a bus bar and then all of your loads can have the negative wire go to the bus bar where they are all locally connected and easy to check for good connection.



if you want a chassis ground, just take a wire with a ring terminal on the end and screw/bolt to the frame. obviously you will want to remove paint and expose bare metal for the ring terminal to make best contact to the metal frame and each load will also require a way to fasten the ground wire to the chassis. that is more prone to corrosion and problems. the only reason to use a ground strap would be if you are using the tool box as a chassis ground and need a good way to electrically connect the tool box to the trailer frame.

 

[smritte]

On mine I run a 10 gauge from the trailer plug to my tongue using a heavy copper lug. The bolt is mounted with a shake (star) washer under the lug. My battery will have something similar in a 8gauge, to the same spot (I like them hooked together). Inside my battery box I run a terminal block similar to what grubworm mentioned. This cleans up my wiring if I have several things wired in there. As of now I have a charger and a solar controller in my trailer/battery box.
Any wiring going through the trailer box goes through a gland nut for water proofing.

 

[dchurch]

I have a similar setup and yes the electrical box is grounded (bolted) to the trailer frame. The shunt is connected to the metal tool box. If it's aluminum galvanized fasteners are recommended.

 

[Anak]

I highly recommend the use of a conductive grease such as Ox-Gard : Ox-Gard

Wherever you have to remove paint in order to get good contact you are asking for corrosion. A good conductive grease will help prevent the corrosion and will improve the quality of your ground connection. Given that you are working on a trailer it might be worth your while to re-do every single ground with Ox-Gard. There is some sort of trailer ground gremlin that is just as bad as the Christmas light tangle gremlin.

 

[M Rose]

…
Where I have a slight question is with the grounding. I normally have a common or earth ground would be the frame of a car or whatnot. I'm just not sure when it comes to the making in the toolbox. can I just mount a grounding plate to the tool box? do I need to ground the toolbox to the trailer itself?

Thank you guys for any help

Usually I do both. I run three main grounds. One ground goes to the frame of the trailer, one to the body of the trailer, and one to the power distribution center. All three grounds run back to the battery negative. Also I tie all three grounds together for redundancy. That way I always have a ground.