The AC850A charger can recharge up to 4 BAT850 NiMH batteries at one time. 
The specifications for the AC850A are as follows:
AC850A CHARGER
*LED indicators for: Power - Red
*Charging/fault - Solid Amber/Blinking Amber
*Ready (charge complete) - Green
*Each charging bay operates independently of other bays.
*Automatically detects and will only charge BAT850 batteries.
*Maximum charging time is approximately three hours for a fully discharged battery.
*Each charging bay automatically terminates the charge cycle, allowing batteries to be left in the charger indefinitely without damage.
*Ambient temperature range for charging needs to be between 0°C and 40°C.
*Typical power consumption, with four batteries loaded, is 25 Watts.
POWER SUPPLY
*Universal power input of 90 - 250 VAC @ 50 - 60 Hz
*UL, CSA approvals; CE mark, TUV (GS) mark, and CB report