I just recieved my ZBook G3 Studio and sometimes the battery appears to take a long time to recharge. In some cases it seems to take 20 minute to increase by 1%. I haven't done any offical tests but it seems that if I unplug/re-plug in, the power cord the rechardge rate improves.
I've got a couple ideas to test - wondering if going into, coming out of sleep mode might be were things go wrong.
As it seems it is a flaw hidden somewhere between the bios and the drivers. It also seems it is an old problem which appears to happen to different HP Laptops. They could have solved it by now as the problem seems to be a few years old.
I thought I have a high end product and I found myself with problems like this (just installing Windows 10, proved itself as a big challenge)... And they want to compete with Apple.... 😄 :-))