Nikon D6 Reference Manual page 1168

D
Warning Indicators
•
If the "L" and "R" chamber and calibration lamps flash on and off in
sequence when no battery is inserted...
...there is a problem with the charger. Unplug the charger and consult a
Nikon-authorized service representative.
•
If the "L" and "R" chamber and calibration lamps flash on and off in
sequence when a battery is inserted...
...a problem has occurred with the battery or charger during charging.
Remove the battery, unplug the charger, and consult a Nikon-
authorized service representative.
A
Charging and Calibrating Two Batteries
If batteries are inserted in both chambers, they will be charged in the
order inserted. If a calibration button is pressed when either calibration
lamp is flashing, the charger will calibrate and then charge whichever of
the batteries was the first to be inserted. The second battery cannot be
calibrated or charged until the process is complete.
1116 Specifications