Battery Warmers

EDIT - DO NOT USE THIS TECHNIQUE - IT DOES NOT WORK. See this post for why.

Despite a healing arm, I managed to find time over the past month to do some work on the battery warmers. I started with GroQuick heater cable. The instructions say not to allow the cable to self-intersect, so I designed a foam structure to hold the cable in place:

It goes between the batteries, like this. Fortunately, the AGM-1280T batteries are just smaller enough than the US-8VGC that this all fits in the existing box:

I laid out the pieces so I could make a PDF template for cutting:

Since I'm healing, I enlisted the help of a henchman. This is my daughter KatC's friend Naiche:

He helped me cut the foam and aluminum pieces for the warmers:

I used a Dremel with a 1/4 inch bit to rout nice even grooves for the cable in each piece:

Here is the biggest warmer in progress. First, the cable goes in the grooves, up to the point where it must go *through* the warmer to catch the other pieces:

A loop is pulled through to the back:

And one of the other pieces put in place, with the cable inserted in the groove:

Most of the extra pieces have two sides, a mirror image of each other. The cable goes back up and around:

The last piece on the rear warmer ends like this:

As you can see, the warmer cable is just a little too long. So, I cut it off. To make it work again, I need to crimp the two internal heating elements together to make a circuit. First, I stripped off about an inch or so of the exterior insulation. You can see the copper grounding braid peeled back and about ready to cut off - you don't want to accidentally ground your heating elements:

In this blurry picture, you can see the next step - the red central insulator is split to reveal the two finely wound heating elements:

The two elements are twisted around each other and bent over to create a larger footprint for...

...crimping a closed-end connector on.

Finally, heat-shrink tubing (with built-in glue) is applied - the glue lets you pinch the end shut:

Lastly, the aluminum facing pieces are installed. They are held in place with heavy-duty duct taping - actual duct tape, of course, withstands heat (since it is intended to be used with heating ducts):