The batteries that comes with the TX that I don't use when I purchase a complete radio system
instead of getting a flight pack when i add more models to my fleet.

and whatever comes with radio system and maybe buy an extra pack of batteries wherever i make
the purchase of whatever I'm purchasing from tower, because they get me buy that discount thing.
The more i buy..I'll get a discount. So i'll add an item to get the discount..but it's like a wash sort of.
I just have an extra pack of batteries