[EricH]

I can't think of any rule about having a deep cycle battery on a cart per se. However, the one caveat on that is that safety is going to be probably your #1 driving requirement, even above having all the appropriate space. (Not that space will be an issue, necessarily.) The main breaker that cuts the battery out of the system is an excellent start.

Now, the question then becomes: Where do you plan to use this cart, primarily? Obviously, in the pit, which has a power drop (thereby making the large battery unnecessary); where else do you anticipate using the cart (and what are the odds of a power outlet being nearby)?