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.
@kingharold Thanks for relating the stories about your wife. That is a rare occurence I would say! Though my wife doesn't share my same enthusiasm she gives me a lot of leeway; but if she didn't I would take it! I know we have to compromise but I worked for it, I earned it and I can think of a lot of other things worse than enjoying music. WAF be damned!
First, my condolences to you, Kingharold. So sorry to learn of your recent bereavement.  Sounds like your wife was a wonderful person.

Second, having been the first to recommend substitution of an Optima auto battery for the $1200 Clearaudio battery supply, I would point out that Optima batteries are sealed and do not vent any noxious gases, ever. Noromance makes a valid point that an unloaded car battery will make up to 14V when fully charged.  Whether that would damage the DC motor or not is definitely worth worrying about, but I don't think the danger would be much ameliorated by an in-line fuse.  A fuse senses current, not over-voltage. One would have to determine whether the load presented by the motor will pull down the voltage to an acceptable range around 12V, and if not, and if one were really determined to go this route, one could calculate the current draw necessary to bring down the voltage to the desired range and insert an appropriate resistor in series.  (I really doubt it would be necessary but worth evaluating.) Optima make a sophisticated trickle charger specifically designed for use with their batteries.  I recommend that too.  I have been using Optima batteries for 20-25 years on one or another classic car in my closed garage, with nary a problem.  I am sure some of the smaller size batteries discussed here would also work, but there you would have to worry about its maintaining output voltage over the course of a long listening session, because in my experience battery-powered audio gear does not sound good with charger in operation.  Smaller batteries tend to have less capacity to store current. And finally, I did find that capacitance in parallel with the battery output did audibly improve sonics, for whatever reason, in my one long term experience with battery power.  I used a couple thousand microfarads in the form of 16V electrolytics wired in parallel.

But third, I also like what Bill said about using a regulated linear power supply.  I am sure you can buy a good one off the shelf for less than half of $1200.
No problem, charge away! Just make sure the battery is well ventilated. Lead acid batteries make hydrogen gas which is explosive. Enclosing it in a cabinet is a terrible idea.
My deepest condolences. I can’t imagine how difficult that is for you. I met my partner 35 years ago in graduate school. She had just done a marketing project on high end audio and knew someone that had purchased two Threshold S500 amplifiers! I couldn’t believe she actually ever heard of the company… what was she, one of three in the USA? I had purchased one ($5,000 in 1982), I took out my first bank loan to buy it. She had also just purchased what would be a very respectable budget high end system. Obviously I was enthralled. We have been together ever since. She has understood and at times encouraged my obsession in being an audiophile. However, I  learned about SAF… spousal acceptance factor. One thing most of us can be sure of is that car batteries in the house would not be within the house would ever be a possibility. She must have been an amazing woman. I can’t imagine how I would cope.