How can I know if an on board charger is actually charging the batterys. Been having battery issues w/ the HB 898 "shutting off" when starting the motor. HB support said it is a battery issue. Asked if they had similar issues an they said "no." So...I'm suspecting the on board charger might be the culprit. It is 5 yrs old. Anyone have a suggestion on how to test it to see if it is doing what it is supposed to do ???