Look what I found on my shelf.

So turns out I already had an 12V 18 Ah SLA battery in my garage. Couple years ago I bought an old razor scooter from a neighbor's garage sale. Bought the battery to try and fix the scooter but the controller circuit board was fried so I tossed the scooter. Sadly I didn't think to keep the motor which worked. So I just need one more battery for my currently theoretical R2!