Isolated Habitat Box Grounding Question

[Fenderfour]

The camper on my truck is isolated from the frame. it rides on fat rubber bushings to provide some flex for the frame. I'm pretty sure i want a ground to frame connection for my camper electrical system, and I'm looking for a good way to do this. This isn't a new problem with all the composite habitat boxes out there, but I'm not finding much online.

I have some ideas:

1. Ground the aluminum frame of the camper to the truck frame using a ground strap. Ground the camper electrical system to the camper frame.
I like this option, as it is easiest to keep the camper sealed as-is.

2. Run a bolt through the camper to a ground strap connected to the frame, and connect the camper electrical system to the bolt.
Ok option, I need to waterproof one bolt.

3. Run a fat from the camper electrical system and connect it to the truck frame.
Requires a big hole and a gland fitting. Not preferred.

open to other ideas as well.

 

[DiploStrat]

I'll play.

Composite box, batteries in the box, inverter/charger mounted outside the box, in an aluminum box.

Solar charging works perfectly.

Shore power charging works perfectly.

Engine/alternator charging was poor, almost nothing.

Looked at the batteries - nice big positive and negative cables. Checked everything, even replaced battery to battery charger from one company with one from another company. (Both good companies.) Spent literally years working with companies and techie friends.

Finally, it dawned on me. The ground went from the battery to the inverter/charger, but never reached the frame. Checked again. Nope, no connection.

Added a jumper from the negative of the inverter/charger to the negative terminal of the starter battery and boom! Perfect charge.

So, there is no point in attempting to ground the composite box, but, as noted, if your camper battery is inside the composite box, you probably want to be sure that it is grounded to the negative terminal of the starter battery. In my case, it was easier to make the connection there, than it would have been to ground to the frame.

Offered in the hopes of saving you a few years of troubleshooting.

 

[Fenderfour]

I'll play.

Composite box, batteries in the box, inverter/charger mounted outside the box, in an aluminum box.

Solar charging works perfectly.

Shore power charging works perfectly.

Engine/alternator charging was poor, almost nothing.

Looked at the batteries - nice big positive and negative cables. Checked everything, even replaced battery to battery charger from one company with one from another company. (Both good companies.) Spent literally years working with companies and techie friends.

Finally, it dawned on me. The ground went from the battery to the inverter/charger, but never reached the frame. Checked again. Nope, no connection.

Added a jumper from the negative of the inverter/charger to the negative terminal of the starter battery and boom! Perfect charge.

So, there is no point in attempting to ground the composite box, but, as noted, if your camper battery is inside the composite box, you probably want to be sure that it is grounded to the negative terminal of the starter battery. In my case, it was easier to make the connection there, than it would have been to ground to the frame.

Offered in the hopes of saving you a few years of troubleshooting.

Thanks for this.

My preferred option is to run all loads back to the negative bus and let the isolated system sort itself out, but all the build info online says to ground the negative bus to chassis as well for safety.

Since I don't have DC-DC charging form the engine, I'll probably just run it isolated.

 

[DiploStrat]

While you are at it, you probably want to rethink your decision not to charge from the alternator.

My experience is that you can't have too many charge sources.

It is 105F at 8:30PM and, after about four hours of air conditioning, I am going to have to plug in. I'm down to about 70%.

 

[Fenderfour]

While you are at it, you probably want to rethink your decision not to charge from the alternator.

My experience is that you can't have too many charge sources.

It is 105F at 8:30PM and, after about four hours of air conditioning, I am going to have to plug in. I'm down to about 70%.

My alternator is either 40 or 60 amps. It's attached to a 30 year old NA diesel from Toyota. There's lots of reliability in there, but not a lot of capacity. Pretty sure the DC-DC chargers will over work that poor little fella.

I don't plan on having AC in the camper. It's more like a rigid tent with a queen size bed and some lighting. It means I will be uncomfortable, but that's fine. I've spent a few weeks in the Nevada desert with less.

 

[DiploStrat]

Looks like a fun project!

I crossed the Sahara in a Blazer, but now that I am older and uglier, I want a bit more long term sustainability.

All the best on your build!

 

[Verkstad]

If your camper has truck powered marker lights, brakelights, etc. You pretty much need to bond the truck frame to camper frame anyway.

 

[Fenderfour]

If your camper has truck powered marker lights, brakelights, etc. You pretty much need to bond the truck frame to camper frame anyway.

It doesn't. The tail lights are on the rear bumper. It's not long enough to need side marker lights. But, I may add some and this is a good thing to be aware of.