Double negative

[Vizoo]

Hello!!

Guys I need some help from electrical experts. I'm converting a step van into a motorhome. It is all aluminum so ground (-) is everywhere and decided to keep the car battery (electric circuit) and the house battery (electric circuit) totally isolated from each other. So I run a negative wire to each device but after finishing I went to test all wiring and that is when things got crazy. After many hours trying to understand why, I finally got it. The housing of the Outdoor LED (C) and the housing of the Heather (D) are metal, grounded and have been bolted to the chassis. As a result I have my "isolated" house electric board no longer fully isolated.

I know that the (-) from one battery and the (+) from another does not close a circuit but I can't figure if this situation generates a problem or not when all is connected and running.

All inputs are welcome!! Thanks.

 

[Vizoo]

You dont need to keep negatives isolated. They can be all bonded together and chassis grounded.
In fact they have to be if you charge the house battery from your alternator.

Indeed, it makes sense. I was so focused on keeping the house electric stuff isolated that it didn't occur to me. I was freaking out when I used the multimeter to check the wiring. I guess I would have find out when installing the isolator . So, a negative bar can have as many batteries attached to it and it would not be a problem as long as each positive goes straight to its device, right?

 

[mudraider]

Yes

Sent from my pretty good android phone

 

[Vizoo]

If you are so mechanically inclined... You can replicate what i had done on my large camper Casa Azul, configuring your motor to power 2 alternators. That way your motor and home bank are 100% ISOLATED!

That raises two questions:
1- Why did you do it?
2- How did you fix the isolated alternator in place? How did you avoid the casing to be grounded like the other one?