After sitting all winter, I started my Kubota and did a small chore. It struggled a bit to start, so I decided to put the trickle charger on the battery. When the battery was charged, I went to start it and nothing happened. All the dash lights are on, including the glow plug. I hooked the charger up while it was plugged in and mistakenly hooked the negative cable first. What did I do to the tractor?