Originally Posted by
dabac
Depends on what you are talking about. Heated soles and gloves work OK. A heated vest would be more challenging, but they do exist.
I run my soles off 18650 cells, one for each foot.
0.8A gives me just shy of 3W for about 4 hours as a theoretical limit.
IRL, I begin to feel the fade after about 2 hours.
Now, "any length of time" may obviously mean different things to different people. But 2 hours full function and one hour more of acceptable function is enough to be useful IMO.
For my part, unless it's really bitterly cold, I don't need to run the heaters continuously. I probably use a duty cycle of 1/3 or thereabouts, which stretches use time considerably.
3 watts is very little heat (my heated motorcycle socks were 13 watts). If the heat is spread over the entire sole, how many square inches is that; maybe 30 for an adult. That amounts to 0.1 watt per square inch. If concentrated in the toe area maybe it's 0.8 W/sq. in. which is pretty puny.
If you figure a similar watt density for gloves the wattage will likely need to at least double and for a vest you'll need an awful lot of watts even just to warm your chest. Starts adding up to a whole bunch of those little 45 gram batteries or a much larger battery.
It's not completely useless but I think you can get a lot more benefit/weight from high quality clothing than you can from heated gear that has wattage that is low enough to run off a battery.