Good question. depends on the AA batteries. The charger puts out 800 ma per hour. I don't know if the charger goes to trickle once the batteries have charged. So I have 2500 Mamp hour AA batteries, so 7500 Mamp total. 800 mah into 7500 you get 9.35 hours minimum to get a full charge. Freescan defaults to a 10 hour charge. After the batteries are charged, usually just plugging into a wall at night, you are good to go the next day. I have a MAHA charger also, takes less time, though the output is higher, the formulas work. Playing around with Freescan to say 7 to 10 hours, is fine. I don't think Freescan really controlls the wall wart but over night charging is fine. I have found that taking the batteries out and plugging into the wall, you don't "boil" th batteries, and you can safely monitor all day long.