On the front of the transmitter there is the battery charging indicator light and when the battery is charging this indicator will light up RED. NOTE: Any time the battery is charging this light will be lit RED and it will NOT turn off until the headphones are removed from the charger. The batteries cannot be overcharged.
In a situation where the battery does not appear to be charging there are a few things to check.
Firstly make sure that the batteries in the headphones are rechargeable 600-900 mAh NiMH batteries as standard alkaline batteries will NOT charge.
Secondly make sure that the batteries are correctly aligned and securely in place. Occasionally the batteries wiggle loose and causes the non-charging issue.
Thirdly ensure that the power supply is connected into the transmitter and into a functioning electrical supply. NOTE: Sometimes when the power cable is connected into a power strip the power strip is not functioning correctly or not providing enough power for charging so it is advised to connect directly into a wall outlet.
In order for the battery to charge a good connection needs to be made between the contact points on the headphones and the charging cradle. To ensure that a good charging connection is made make sure that the ear cups are not extended as extended ear cups can cause the headphones to not alight correctly and hence not charge. On occasion when the headphones are brand new and the headband cushions are stiff or the headphones are older and the cushions have started to spread out the cushions can be preventing the headphones from making contact with the charging cradle. In a situation like this applying some downward pressure to the headphones when they are on the cradle can ensure the contact is made.
If none of the above solutions work then it is recommend that you try an internal electronics reset by disconnecting the system from both the audio source and the power source and leaving the system disconnected for 15 minutes. This gives the unit a chance to reset back to factory settings. At the same time you should check the batteries and change them if necessary. When changing batteries you want to use 600-900 miliamp NiMH AAA batteries. After the reset period you should reconnect the system and test.