This is what I came up with to combat having to take my battery off to keep it warm on my Ion.
Wifey made it in about an hour.
Reflectix lined with a waterproof/windproof nylon shell (tent material). Used black as it will draw heat naturally from the sun as well.
One Hand warmer here for the front of the battery.
One had warmer on left and right side
Buttoned up
Front shot
On the Ion
I havnt tested it yet, but my hope is this will keep it warm enough to leave it on the auger in the coldest of conditions.
Without having to remove it to keep it warm.. May not need 3 hand warmers either, but testing will tell.