Originally Posted by SteveM732
If you are going to charge from USB you must as it is a ~5 volt supply. If you charge using your own charger then you won't have any issues with over charging, but you won't have the circuit to protect you from over discharges.
Steve summed it up and as usual he's Johnny-on-the spot with a link. As I mentioned in the other thread the main purpose in these spy cams is to prevent discharge. Without it the Key Cam would be a "one use" camera.
Overcurrent and overvoltage functions never used because the cameras do not draw very much even when taking pics (50ma in the ones I measured) and the charging circuit never went above (4.19v worst case in mine).
PS However note that, like the Silverlit ones, it does not function as a charger and will not work simply connecting to a 5v supply.