Yes you definitely need a least one battery.
I have 2 group 27 wet deep cycle batteries. I am 70 yo
, and not unusually strong or fit. I thought out how to do it. I brought them one at a time up a step ladder to my Tartan 27 and then down into the cabin. Just to let you know, it can be done.
Men usually have much greater upper body strength and maybe this is one of those times to ask for help from one! A block and tackle setup is safer and easier to be sure. I do not think, if you keep the weight close to the hull and not swung far away, you do not have to worry about the stability of the boat on jack stands. Good luck!
Mary
HotFlash
T 27 Yawl