Hi, I have a 1998 , toro /wh 520 xi. Has a Kohler 20 HP, 445 hours, recently, the battery light comes up on the dash,while mowing after a hour of mowing, battery is completely drained, and will not start tractor without a jump start. 1) i replaced old batt with new battery 2)cleaned connections 3) same issue,with dis charging, with new battery install voltage check at battery not running = 13.36v voltage check with engine running half throttle = 12.1 and the longer the eng runs the lower the volts drop,light on dash comes on, and if i mow,battery is dead in 1 hour. Any ideas what i can check or do? Thanks jim