Can I charge my phone when I using my heated jacket?
Indeed it's a funny question.
Most phone is charge by usb port and the above question change to:
Is your heated jacket's battery has a usb port?
If yes, we then serious to the above question: Can I charge my phone when I using my heated jacket?
You can charge your phone separately, and when using the heated jacket, it will cosume most of the source of the battery and you have to look into the user manual for details.
Normally it will set aside no more than 5v 1a for charing your phone at the same time.
But if it's not so nessary,I am not suggest people to do so as this will let the battery as it's high level output and will heat up the battery fast.