My Samsung Galaxy note 9 charges slowly sometimes and quickly other times. Why?

[Android Central Question]

On more than one occasion I've woken up to a battery that has only charged 10% or less overnight, despite a fully functional charger. Most of the time it charges to 100%. I've noticed this variance in charging speeds on a number of occasions and wonder why it seems to charge quickly at times and slowly at times and a couple of times didn't charge hardly at all.

 

[Rukbat]

When it was charged to 10% (neglecting the fact that you're killing the battery by discharging it any further than 40%), you probably didn't have the plug plugged all the way in. You should be able to feel the "click".

 

[Kodak2]

Faulty charge lead or charge socket if not above. +1 on not discharging below 40%.