[Psychobabblez]

for about a week now my Lumia 640 XL says that the device is charging slow and I should use the original charger that came in the original packaging even though it's plugged in with the original packaging. not sure if this is a battery issue since I tested out other usb chargers.

[T Moore]

What is says and what is really happening may be two different things. Get a good battery app that will give you the charging rate so you. Saying it is charging slow doesn't give much info.
Battery app by Semenov, get it. In settings turn on 'display rate on main screen' to get charging and discharge rates. 15 to 20% charging rate is what to expect.