air travel

Have any of you traveled with a TENS unit in recent years? I'm using one for physical therapy, and don't know if it's ok to bring in a carry-on bag. If it needs to go in checked luggage, does the battery need to come out? The TSA website is not particularly helpful. The TENS unit is not one of the electronic items they specifically say is allowed for carry-on, but they do say, "We recommend keeping fragile or expensive items with you in your carry-on bags," so I'm not sure.