Hey Charles,
According to the Roomba 650 trouble shooting page there could be multiple issues with your roomba. 1) Your target station is too far away or 2) There is an issue with your batttery. To fix the first issue you should move your home station to a more central location. For the battery problem I would suggest cleaning the nodes on the battery first then start to think about buying a replacement battery. You should check out the troubleshooting page at
[[iRobot Roomba 650 Troubleshooting]]