I have a P38 and would like to put in a secondary battery. I'm considering running wire from the battery in the front to the rear load space under the truck. I'm concerned that when fording a river or driving in deep mud that I may short the connection out.

To add complexity I would eventually like to put a winch on the front that will be supplied by this system. I know the warn winches are waterproof but how about the wiring that supplies them?

Does anyone have any ideas on how to waterproof the electrical system?

 

You don't need to worry about shorting out a battery connection underwater. It's only high voltage that's an issue with water. Or delicate electronics.

Also, if you want a battery mounted in the back, you're better off putting your starting battery in the back, and your winch battery where your current battery is. To properly supply a winch you'll need about 4/0 cable if you have the battery in the back, which would be pretty expensive.
Your starter draws less than 150 amps and that for only a short period. A winch can draw 300-400 for an extended time.

 

That's some excellent advise. I hadn't thought of putting the starting battery in the back.

Some one was nice enough to donate a huge amount of welding cable that had previously been used on a tow truck to supply jump start power in the front and rear of the vehicle. I'm planning on running the power around in that.

Regarding water and electricity. I know that perfectly pure water (distilled) doesn't conduct electricity at all. But if there is any salt of any form in the water it will conduct pretty well.

I could totally see issues with high frequency and water. It would tend to arc.

I'm pretty sure that if the wire running to the back were exposed and I drove in water then the power would flow through that wire to the frame (ground) and back to the battery.

Any ideas how to prevent that problem?

 

No, it wouldn't. People submerge their batteries a lot, starters even more often, with no issues at all.