Sorry so late in replying - in case anyone is curious about the solution.
First - my dealership was slow in responding because they apparently never got my first round of emails, then the dealership manager died.
Once I got ahold of them, they were very supportive and basically their answer was "you're covered -- go buy a battery, fax us a copy of the receipt, and we'll mail you a check." This was also the answer they got from Mahindra. (they were willing to eat the cost of the battery even if Mahindra hadn't OK'd it)
Apparently the batteries in the 10 series machines come from Korea with the tractors - and it has a 12 month warranty.
If anyone needs to replace theirs, a group 31 (commercial/industrial) 110AH 850CCA battery will fit in the tray just fine for a 3510 or 4110. So will a group 49 or 93 truck battery - but they may not survive the stresses driving a tractor on uneven ground, loader work, etc... delivers
The solution was much cheaper than replacement - and I kicked myself for it.
Corrosion on the negative post under the terminal where I couldn't see it until I pulled the battery and took it to town to be tested by a battery shop. (I had checked all my connections for tightness, but hadn't actually pulled the terminals and reset them - and all tests pointed to a bad cell)
wire brush the terminal, put battery back in, and the tractor fired right up. (sprayed terminal protector on it before closing the hood this time)
anyway, I felt stupid, the dealer and I had a good laugh, and he was happy I didn't abuse his generosity to go buy a spare battery.
