Li-Ion heated gloves

 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 period:

LED: red (high) - 665ms on, 35ms off - 95%

LED: yellow (medium high) - 520ms on, 180ms off - 75%

LED: green (medium low) - 350ms on, 350ms off - 50%

LED: blue (low) - 180ms on, 520ms off - 25%