Tonight I visited my local Batteries Plus retailer. I had spoken to the manager checking prices on Powersonic 12 volt/18amp batteries. Since he knew I worked for the local medical center and these were for R2-D2, he gave me a generous discount. Had I bought these online, the shipping would have been brutal! The batteries are 14 pounds each! (I don't dare weigh my droid anymore!)
These batteries will be hooked up in parallel, meaning two 12 volt/18 amp batteries will give the drive system 12 volts/36 amps (in theory).
Tomorrow I'll have to make some decisions on the 2-3-2 system that is installed. I think it may have to be removed so I can fix the center leg in the down position. I also really need the space inside for the batteries. But...we'll see!