As per the user guide.
"*Charging Notes: When the user uses rechargeable batteries, we recommend to use Ni-MH or Ni-Cd rechargeable batteries. The average current is 200mA. For example, it will take 10 hours to charge 2000mA/H batteries fully. For more capacity battery, the user has to charge them by multi-startup methods until charging is full.
Max charging time: ≤10 hours, the aim is to protect rechargeable batteries or unit from being damaged;
Charging voltage protection: when the batteries reach full-charging voltage,the unit will stop charging automatically to prevent batteries from being damaged;
Battery detection function: the unit can detect the status of short circuit or open circuit with one or two batteries. If Not sure batteries are in good or bad condition, the unit will stop charging automatically in 10 hours. "
Has anybody used the inbuilt charging feature of the AR-1733 and found it does not actually seem to work? I normally get a few weeks of use out of a set of 2200mHa rechargeable batteries, these I normally charge in an external charger but due to our recent move, I instead plugged in a USB cable and enabled the charging feature. This ran for around 8 hours. The next day I only got a very short run time before the batteries shown as flat.