If you look at your batteries and the connector for your battery on your phone, there are 4 pins. This should be the same on all Motorola android phones including the Droid 2. Only 2 of those pins provide power (Plus and minus). The other 2 pins are a data connection with your phone, they provide battery info such as charge levels. Inside the battery is a chip that monitors and controls the charge for the batteries and provide a battery meter info for you phone.
Make sure those 4 pins are clean on both the phone and the battery pack. There is also the possibility that the batteries you purchase on eBay are a 3rd party knock off and not provide the necessary data connections to provide the phone with your battery levels and so on are missing. I would try to go with original or OEM batteries from Motorola first. You can also look for 3rd party batteries form repeatable dealers or retailers.