You didn't mention the model number so I am guessing that it uses Li-ion batteries.
These are not supposed to have a memory problem.
Here is a site that has a good deal of information about all types of batteries:
Maybe you can find something there that will explain the problem you are seeing.
I've got an X-Drive Pro to download photos to when I'm away from home. I also use it as a portable hard drive to transport files between computers. It is taking longer and longer to charge the battery, and I'm getting concerned that a memory phenomenon is at work shortening battery life. Any suggestions to improve this situation?