I've been frostbitten many times, (thanks hockey! thanks motorcycles!) starting when I was pretty young. It doesn't take long for my fingers to become completely unusable in cold weather. I've got every pair of cool gloves ever made. I got mil-spec "mutant-mitts" last year, which are pretty much the definitive glove. They are much too large for doing any work, but great for climbing.
The little powder-pack shake handwarmers kind of work, but not really. When it's very very cold, and they are in my pant's pockets they don't do much at all. And here's a hint: they have a short shelf-life. If you buy them, dig around and check the dates. All of the ones for sale early in the fall are probably expired. I'll use them if they are free.
I got these weird liquid-chemical ones that have a little metal 'snap disk' in them. You bend the disk and they turn solid and get warm. I bought a bunch for very cheap last year, but haven't really tried them at work yet. They get hot at first, but don't seem to last very long. But, I've got, like, a dozen of them
The zippo handwarmer is pretty good and can stay hot for hours.
My Jon-E-Warmers (where zippo stole their idea) are much better. They can stay HOT for ten hours. But, depending on what kind of explosive products might be around, some jobsites won't let you use them. When I found out that Jon-E went out of business, I searched online and bought, like, ten of them. They are my go-to lifesavers. They say that the catalyst filaments wear out over time, but I've had some for years that still work good. And I bought all the replacement packs of filaments that could be found. Hoarding.
I got some rechargeable battery-pack warmers that fit in your pocket and they work pretty well, but not near as hot and long as the lighter-fluid kinds.
I never got any battery-powered gloves, because the first thing I have to do at work is take my gloves off. Trying to work while wearing gloves, or trying to jam gloved hands into your pockets never works.