i agree with the responses above.
go with the hard wired gloves rather than the battery version.
they are not difficult to hook up and you avoid the dead battery problem.
one additional suggestion. buy the thermostatic control for the 12V gloves. it will increase the cost but heated gloves without a thermostat can cause burns which you probably won't notice until it's too late.
the extra expense in well worth it in terms of comfort and safety.