I have a FXDXT that has a OEM AGM in it thats now 5 years old. If it sits for a few days and I take a read just cranking it over the voltage reads 9.5+ -. Voltage after several days of sitting reads about 12.5 12.6. Info Ive read says voltage a couple days after a full charge or ride should still be 12.8. Ive never had a battery stay that far up on voltage that I can recall. Que pasa?