Possibly Dumb Question re:Battery as a power supply

I have bought a new Clearaudio Performance DC Wood turntable.  I plan to drive to the dealer in Atlanta and pick it up next Wednesday.  I have seen the wall wart power supply which comes with the TT, and it is not a pretty sight.  Clearaudio sells an upgraded 12V battery and charger supply for "only" $1,200.00.  I don't wish to present myself as a parsimonious individual,  but $1,200.00 seems a bit steep to me.  I am wondering what problems would ensue if I bought a moderately sized (say 25 or 30 lbs.) , sealed, lead acid, 12V rechargeable battery; attached the proper wires to connect to the TT, and used it as a power supply.  When the battery runs down I could just take it to my workshop and use my electronic, automatic battery charger I use to recharge car, truck and tractor batteries to bring it back to full power.  As little current as the TT uses this shouldn't be too frequent a chore.  It is just a possibility, but if it is feasible I might try it.  I would really appreciate any and all comments, criticism or warnings.