I have a very annoying problem on my laptop Dell Latitude 5420.
It works perfectly fine when the battery is 100% charged (and plugged) or when it is unplugged (thus the battery is discharging).
However, when in charge (and lower than about 90%), the computer almost cannot be used: the mouse moves incredibly slow (similarly for the touchpad). Furthermore, it seems that the hard drive responds very slow: saving a tiny text document (which would usually take a few milliseconds) takes 10-20 seconds.
When I'm at work, the computer is always plugged, and this is not a problem; however, after I use the computer in a train or a plane (hence without power supply), I have to wait one hour before it becomes fully charged to use it − and this is really annoying.
I installed two systems one after the other
1) Ubuntu 11.10 64 bits
2) XUbuntu 12.04 32 bits
The problem was the same in both cases, from the first installation.
I wonder whether it comes from some incompatibility coming from Ubuntu (although this model has been certified for Ubuntu), or from a hardware problem in the computer.
Thanks for any hints