A:Answer I bought quite a few batteries and fully charged all of them before plugging them into a heated vest, wrapped the vest, waited for gift exchanges, and they all turned on immediately
They have another port that a guy could charge his phone but I like to save my battery juice for heat. I charge it after a day or two, depending on how cold our days and nights are here in Wisconsin. I have not let the battery rest with a charge- long enough to know how long I couldn't use it.
Keep two of them for yourselves so one is always ready to use.
