I have a heated undershirt which I use when I have to go out for long periods in exposed forestry, it has 3 heat settings accessed by a front button. It works a treat, the heating pads are on its back, so I would say to anyone thinking of a heated garment consider where the heating pads are located. With reference to battery life, the standard power bank ( battery ) is a 3.7V 5000mAH this will last for at least 4 hrs on max heat, but for all day comfort I also have a 10,000 mAH battery, the only downside is its a little heavier. Both units charge from a USB port or USB mains adaptor and fairly quickly. Various rated power banks are available online, so depending on your use just find the right size battery.
The undershirt washes like a normal garment, the battery is of course first removed ( it normally sits in its own little shirt side pocket ) and there is a plug to be pushed over the wiring connector, which is then secured in the side pocket. It is then placed in a little zipped nylon bag and into the washing machine.
