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Li-Ion heated gloves

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 I have a pair of heated gloves that use rechargeable Li-Ion batteries. They don't really last long enough for a full ski day, so I've wondered about getting extra batteries. The gloves are labeled FieldSheer, powered by mobile warming technology. The Fieldsheer web page  lists batteries for sale, 5V and 7.4V, very pricy. The printing on my batteries is faded, although I now can see it slightly better in the photo I took for this post, but I wasn't sure which voltage would work. I found a same-sized male and female pin jack pair in my part collection and setup an extender cable so that I could probe voltage and current. Using a meter, voltage is about 5V, and the current is sometimes 1A, sometimes off - suggesting a PWM scheme (pulse width modulation). The glove button toggles between 4 heating levels, and holding the button shuts the heating off completely. Using a data acquisition setup (0.05 ohm resistor to measure current), the PWM scheme is easily seen to use a 700ms p
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 The Engineer's Itch We all often come across something that we want to learn about, and it sticks in our mind for a while - kind of an itch that will eventually need scratching. I have collected a number of electronic gadgets that have failed over the years, and I want to figure out what went wrong. I also have a few that are ok but I still want to know more about how they work. This blog is a place to post summaries of what I find out.
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