Swoop223 is spot on folks.
A set of deep cycle batteries are OK to put on a cart & move lifts around the shop or into trailers but that is all - we did all the time when I wholesaled used lifts. The run time/charge wasn't all that good ~3 hours ( primarily driving). The cart was set to pick up 24v, 36v & 48 v. Plus, occassionally a battery would explode from over charging so we put a lexan shield over the top.
I would hate to say in front of a judge & jury - I made these unauthorized modifications to save money... you loose and maybe more than money.
Shade tree/backyard engineering has hurt & killed folks & there is no such thing as a planned accident. Jacked up pick-up trucks roll over all the time. I knew two young men that lost their lives when there "Cool" truck left the road.