brunnhilde said no to trailer winch battery - part 2

Carrying a tiny AGM battery in the water boiler compartment is a viable solution to power the winch. That avoid the increase in the trailer tongue weight imparts onto Brunnhilde which has a 500 lb maximum. In the existing arrangement, I intended it as a test of concept and planned to refine the design to further optimize it. As it stands it requires the passenger side rear door as well as the water boiler compartment door both be open during the operation.

I want to have the Anderson connector on Brunnhilde side to be placed on the trailer hitch structure to rid the need to open the doors to make the connection. Not just that, I was thinking utilizing Brunnhilde's house battery bank to power the winch, saving even the weight of the small battery. I had considered buying a slightly larger battery in place of the dedicated winch battery. Still I need to address the charging for it if I were to leave in Brunnhilde during the track seasons. Running a properly sized charging wire to the water boiler compartment is a major endeavor I would like to avoid at all cost.

There were a pair of 12V cables in the water boiler compartment which used to power the 120Vac to 12Vdc switch mode power supplies for the DC rooftop air conditioner. When I striped out the Kerstner DC unit I tried to remove both of these defunct low voltage cable to save weight. However I decided to leave it under the vehicle in case I have a need for them down the road. Stripping them out also requires a lot of work crawling under the vehicle and pulling out the cables through some obstacles. I had been so long as to what I did  to ensure the B+ cable does not become an unintended arc welder should the crimped terminals becomes expose and touches the body sheetmetal. I seemed to remember I snipped the hot cable at or near the upstream power source.

I lower the underbody spare wheel where the cables are tidily hidden away from harm and accident. I was hoping the B+ is still hot as I had taped it up really well and secured the end with cable ties so it has next to no chance of contacting a ground. I tested it with a DMM but were disappointed I indeed disconnected it upstream. This is good to know I did the job right 5 years ago, but it means more work now that I want to repurpose it.

When I remove the driver seat to install the power window manual override, I used the opportunity to look for where I severed the B+ cable. I vaguely remember I severed it inside the under seat box where most of the Sprinter's wiring, fuses, and relays are located, as well as the relay to merge the starting battery with the house battery once the engine is running so both can be charged by the alternator. I looked in there, and I could not find the severed cable stubs.

I then search the under body and couldn't find them either. Lastly I looked in the engine compartment. I would then realize again there is this unobtrusive plastic box above the starting battery where the cable passes through it. It is the high current fuse box dedicated for the roof top AC! I removed the fuse so the cable is no longer hot. This turned out to be the best scenario of what I did 5 years ago. I now can have the cake and eat it too.

While the cables are about 20 ft long from end to end, I think they are 8 AWG so more than overkill to power the ATV winch. In fact I will need to reduce the wire gauge to fit the grey Anderson connector that I selected for the job. I have to exercise the brain to figure how to do this properly.

I removed the high current fuse 5 years ago to make the defunct cables safe for tucking them away unused; all I need to do is to install a properly sized fuse for the new application

I even found the original fuse for it but it is a whopping 150A so unsuited for the new application; I reckon I should size it to 60A

This cable pairs are 8 gauge, which are too large and stiff fitting an Anderson connector of the size I chosen. To safely make the transition to 10 gauge I bring the cables back inside the water boiler compartment.

back in they went into the water boiler compartment again

a handy wire gauge chart

I selected the minimum number of parts to purchase to make the transition and install the grey Anderson connector onto the tow hitch. 

the terminal posts allow me to make the wire gauge transitions, from 6 gauge to 10 gauge

Until I receive the needed parts, the well laid plan is going well. The only thing I am debating is to add a cut off switch to be located in the water boiler compartment or not. If I do it would be cheap China made one as the marine grade ones starts at $50. I already have one of this commonly installed in track cars but it requires cutting into a firewall or fabricate a bracket to install it, which is too much work as well as taking up too many cubic centimeters of precious space.

this is like the one in Brunnhilde that shuts off all loads to the house battery bank

I found this nice looking Chinese made one much suitable that can be simply screwed onto a flat surface.

I think I would add this to the cart 🙉