When I bought this tractor last year at this time the dealer had put new batteries in it because someone left the key on and it wouldn't start. They put in 2 large 6 volt batteries (Exide F-3EH). They are dead now and I think just need a recharge. Not sure why they are dead but that's for a topic for another time. 
Question is what are your thoughts on this set up for the batteries? I was wondering if 2 12v in parallel might be better. This is in NY where winters can be pretty tough.