I rode for several hours in 30 degree weather and after hallucinating being in a bath for the last hour I got this. This one I thought I'd try because it runs off any decent powerbank with USB A.
I have a few 10,000 Anker powerbanks and I love the vest. I like that it doesn't have a collar and to answer a question in this thread, it runs for several hours on medium, which is pretty darn warm. I wear it over my base layer and it's quick to heat and change heat levels. I'm super happy with it!