Nokia MD-3 Manual Del Usuario página 3

ENGLISH
Set up for use
The speakers can be powered by three AA batteries or the supplied AC-4
charger. Note that the AC-4 charger does not charge the batteries.
When you use batteries, alkaline batteries are recommended.
To use the speakers on battery power, to install the batteries, open the
battery cover at the back of the speakers by pressing the two catches,
place the batteries as indicated in the battery compartment, and close
the battery cover by pushing it in place. During long periods where the
speakers are not used, remove the batteries to prevent damage from
battery leakage.
To use the speakers with the AC-4 charger, connect the charger to a wall
outlet, and plug the charger cable to the connector at the back of the
speakers.