Battery not charging

There could be several issues here as to why the battery is not charging. There is not a lot of info to go on here but I decided to give you the link to the Motorola tech service manual for this device in hopes that a reference material will help you out here. My first suggestion is measure the output voltage with a multimeter at the charging port to make sure that the current is of proper voltage and stable. I would then make sure that the batteries are capable of holding any type of charge. These problems are usually due to the source of the power and not the receiving end but in this case all needs to be checked for sure. Good luck and below is the link, just copy and paste into the address bar of your internet browser. make sure to hit save file so you have it for future reference. ParrotHead PC Repair

http://www.eserviceinfo.com/downloadsm/5153/Motorola_GP-300.html

The batteries not charging only means 2 things. the cells in the battery are at their end of life, or the charger's power output is going low because of worn coils or burnt coils.

Best deal is to get both pieces tested so you'll have an idea on which one to replace.

Battery Care Tips These battery tips will help you obtain optimized performance and a longer life cycle from your Motorola rechargeable battery.
1. Charge your new battery overnight before using it. This is referred to as INITIALIZING and will enable you to obtain maximum battery capacity. a. Nickel Cadmium or Nickel Metal Hydride: 14-16 hours. b. Lithium Ion/Polymer: 1 to 2 additional hours after the charger light turns green.
2. New Motorola impres batteries, when inserted into a Motorola impres charger, will indicate a calibration cycle by displaying a steady Yellow< indication on the charge status indicator. Allow this calibration process to complete by not removing the battery from the charger until it has completely charged and displays a steady green indication.
3. In order to minimize capacity loss and cycle life reduction, new, NON INITIALIZED batteries must be stored in well ventilated, cool and dry locations. Batteries stored in these conditions may be stored:
a. Nickel Cadmium up to 2 years.
b. Nickel Metal Hydride up to 18 months.
c. Lithium Ion/Polymer up to 18 months.
4. If used batteries are to be removed from service for extended periods (greater than 30 days) they should be discharged to about 50% of their capacity before storage in a cool, dry location.
5. Batteries which have been in storage for more than two months should
be fully discharged and recharged.
a. Nickel Cadmium or Nickel Metal Hydride: 14-16 hours.
b. Lithium Ion/Polymer: 1 to 2 additional hours after the charger light turns green.
6. When using a Motorola rapid charger, leave the battery in the charger for an additional 1 to 2 hours after the steady green light appears. (Applies to non-impres batteries only.)
7. Do not leave your radio and fully-charged battery in the charger when not charging. Continuous charging will shorten battery life. (Do not use charger as a radio stand.)
8. Only charge a battery when it needs it. If it is not fully discharged, do not recharge it. We suggest that you carry a spare. This is the most cost effective solution for users requiring longer operating time.
9. Do not return fully charged non-impres batteries to the charger for an "extra boost." This action will significantly reduce cycle life. Repeated short cycle charging of non-impres batteries will shorten battery life. (Do not use charger as a radio stand for non-impres batteries.)
10. Stabilize batteries to room temperature (72ºF) before charging. Charging below 40ºF and above 104ºF will decrease cycle life.