a few times a smartcraft warning has popped up saying hi voltage and once low voltage and then after running the air for a few hours, then shutting it off and a few mins latter starting the engine the low voltage warning came on and no battery power. when running the air i had the battery charger on. pluggged back in , recharged for ten mins and started up. green light on charger is on . have noticed that smartcraft voltage reading flucuates between 11.1 and 13.5 but most of the time is 12.4. whats going on? starr