Default HTC One slow charging when on

Hi All,

I experience charging problems with my HTC One when the phone is turned on.
Normally I plug in my phone when I go to sleep and when I wake up it's fully carged.
But now when I wake up about 7 hours later the phone is only 50-60% completed.
I turned off my phone and continued the charge and after 1h30 it reached 100%
With the phone on it would take about 6 hours according GSam Battery Monitor.
This is already the second night I'm having troubles with charging normally...
Note that 3 weeks ago I bought this car charger with 5V/1A output.
Since then I use it every weekend in combination with a holder for GPS.
Could car charging the device while using maps hurt my phone's battery?
My HTC is completely stock so I'm not sure if a battery calibration works?

Kind regards