Hi! I recently purchased a HP Probook 4520s second-hand, and installed a 500GB HDD and 8GB RAM and Windows 10 x64. It works fine plugged in but the second I plug it out the battery time drops to 45/30 minutes in the Windows taskbar and the battery decreases rapidly. The system also becomes very unresponsive and borderline unusable when unplugged. This is making the laptop very unusable. Help would be appreciated!