Simple fully isolated solar power system?

[Alfie Dring]

Hello, :)

I'm about to install a simple 12VDC electrical system in a campervan. I want this system to be fully seperate from the engine battery and the vehicles other electrical systems and to only serve the "house in the back" so to speak.

I'm a bit confused about the role earthing plays regarding safety on 12v systems? I'm also reluctant to ground or earth the new electrical system to the van's chassis as I dont want the two systems to have any interplay with each other. The box of the van is glass reinforced plywood and its construction means i can wire up in such a way that only a serious mishap (crash etc) could cause any part of the systems to be shorted to each other.

Below is a circuit diagram of what im thinking so far. The fusebox would be the automotive type with blade fuses of the lowest value possible, other than that there are no safeguards?

http://img225.imageshack.us/img225/6606/turtletonelectric01.jpg

Thoughts/ opinions / improvements and even outright tutting will be very much appreciated :D

Regards,

Alf

[Rob Beckers]

Hi Alphie,

Grounding is about safety for the user, it won't "connect" the two systems (on-board electricity and your solar system) together.

There are two aspects to grounding: One is that all metal parts (conduit, boxes, appliances) are normally connected to ground. That way you won't get electrocuted if for some reason 120V ends up connected to that metal. This really is about safety and I would not skip that. Even for a 12V system there is the odd chance that somehow 120V (or more) finds its way to one of the leads and any fault to ground would energize parts you can touch.

The other aspect is that in North America usually one of the leads of a DC system (usually the negative lead) gets connected to ground. That has more to do with convention than safety, and other places do this differently (they leave both positive and negative floating). I don't see any safety issues with not connecting the negative to ground. The one down side is that it won't alert you (by blowing fuses) if for some reason the positive gets connected to ground accidentally, and that could give you a false sense of security when working on the system (a tool connecting the negative to ground would complete the circuit and those batteries can easily melt metal!).

Hope this helps!

-RoB-