Paranemertes:
@PeterH, sorry forgot to mention sealed lead acid batteries. I have access to welding and metal working equipment so i was intending on modifying the frame so they would fit and be protected.
Worth checking the current ratings then, since sealed batteries tend to have low charge and discharge currents. But mainly I'm concerned about the physical size and weight of the things. Have you seen and picked up a battery of the type you're proposing?