i wanted to try to run it off of an auxilery battery under the seat. luckily i found myself around the campfire with an electrical engineer and got some valuable advice. firstly you need to use a deep cycle/marine battery type battery. i dont understand these things so well but basically these batteries are designed to be charged up and run down repeatedly unlike the automotive batteries most of us are more familiar with.
as he is a nice guy, he advised me on what kind of battery i needed to run my Warm and Safe 90 watt jacket for two hours:
90w for 2 hours at 12 volts.
90w/12v = 7.5 A
7.5A x 2 hour = 15 A hour needed
since i actually only ride around 45 minutes each way and i dont turn the jacket up much higher the 50%, i went with a 12V12Amh battery as i wasnt sure what would fit under the seat. i bought this battery from amazon. it is enough for my needs and still allows me to put my road emergency gear and my 12 inch laptop under the seat. if you want to run for longer or use heated gloves you might consider the 20Amh hour battery assuming it will fit under your seat.
so far this system is working very well for me. however, the real test will come when it is down close to zero in the morning in a few weeks!
i am using a CTEK smart charger. i soldered the charger connector and the warm and safe jacket socket directly to the battery.


