Originally Posted by Rep
I had three by the time I finished the game. Two of them were just scattered around the level, so there might still be more.
I don't think you can upgrade them, because I never saw an option to do so. Not like it matters as you don't really need to.
I've only ever had one bot. I can't use it until it returns to the bench, then I pick it back up and get supplies and I can redeploy it again.
I was not aware you could carry more than one. I'm on Chapter 9 and haven't seen any more.