I had some heated socks and they were a disaster. I think they cost about £150 and they work by little plastic inserts with the heating element that slipped into a pocket in the sock under your toes/the ball of your foot. This then connected to a battery pack.
OH bought me them as a present as I have reynauds and so suffer badly with the cold. He quizzed the company on durability and was reassured they stand up to tough outdoor use, good longevity and so on.
Well they last half of a sedate hack then stopped working. He'd bought me an extra pair of inserts as a back up so I tried those just incase it was a dodgy pair and they didn't fair much better.
When we spoke to the company they said it wasn't unusual and that elements would need replacing from time to time- 1 ride a go wasn't time to time in my view. We ended up getting a refund after going through trading standards.
So not a great review from me - tbh the heat holder socks are the best thing I've found, along with Equitector boots (which are a miracle product in my view!)
I'm still hunting for something that helps keep my hands warm though