My M3-C drops to low from turbo when the battery voltage is around 3.6 v. From low it can be stepped up to high. High runs very long after that. I would rather it step down to high directly but I can live with it. My charger indicator light prematurely turns green but continues to charge to 4.2 v after that. A usb tester helps keep track of the status for me or you could just keep it on charge for a while longer and check it with 5 clicks for battery check. Mine terminates consistently and doesn’t overcharge, the indicator is just not right.