I've got a battery heated jacket, kidney pads, and socks. I love them. I'm not in a cold area (zone 7a) but they really help my archery hunting. When I enter the woods in the afternoon, it can be quite hot. I don't want to work up a sweat walking and climbing to my stand. Once the sun goes down, the temperature can drop quite a bit during our October bow season. So, I would either roast in the afternoon or freeze after sunset. I have arthritis, and it is easy to get stuck in a tree after sitting for a long period and stiffen up with a temperature drop.
I now dress very light. Some days I wear shorts and a tee-shirt under my coveralls. I typically only use the jacket or kidney belt at this time of year, not both. I no longer get sweated up walking in. When things begin to chill off, I turn on the battery. I can't recall brand, but I know I got a replacement battery from Cabelas. I think it is 7.5v clothing.
I also use it under heavy coveralls in the winter. It works fine for me, but our winters are not like up north. When I was a kid in PA, we used hand warmers that ran on cigarette lighter fluid. Nothing kept me warm enough up there. The battery driven clothing is quite convienent.
Thanks,
Jack