Have I damaged my Lumi 2 by using a fast charger?

[ksks]

I recently bought an Onyx Boox Lumi 2. Today I was using it while it was plugged into the charger, and I noticed its touch screen wasn't responding properly. It was fine when using a stylus, but when I tapped using my finger, the screen went crazy, zooming in/out, registering the tap elsewhere on the screen, just being super erratic.

Then I noticed that when unplugged, all the issues stopped. The problem returned when plugged back in. I was using a new charger at the time: a Samsung fast charger whose output, like many adaptive fast chargers, is "9V 1.67A or 5V 2A".

I know that in theory, this charger is fine to use. Only devices that support fast charging will be charged at the higher rate of 9V 1.67A. All other devices that don't support it will default to 5V 2A, so there is no risk of overcharging at a higher voltage - theoretically.

But what I experienced today seems to suggest that the Lumi 2 was being charged at a voltage higher than 5V, hence making the touch screen erratic. I've read that the wrong voltage can do this to capacitive screens.

Before this I'd been using a slow charger, 5V 1A, which worked fine, but I thought its lower-than-required amperage would be bad for the battery which is why I had swapped to the new charger.

The Lumi 2 still works fine, but I'm concerned that I've done some damage to the insides and shortened its life. The Lumi 2 is so very expensive and I couldn't replace it if it failed.

Can anyone shed any light on whether my thinking is correct, and whether it's likely that my device was indeed charging at the higher voltage for some reason? Thank you in advance.

[Renate]

Nah, you're probably ok. It's probably noise being injected in from a charger that costs $0.99 to make.

To reassure yourself: First try my UsbMode.apk (in my sig). It will show you touches and you can see if they are jumping all around. You can also go into "Settings > Developer Settings > Show Touches".

Try the Samsung charger plugged in both ways (the AC plug is symmetrical.)
I'd try grounding the ground of the cable, but I don't want to get you into too adventurous territory. If the entire setup is floating it's kind of a gigantic antenna. Plus whatever is coming down your AC line. Plus whatever the switching supply in the charger is generating.

[Arjava]

Renate was right,it was the electrical noise that messed up your touch screen rather than fast charging.
I have had the same experience with my Memo Pad tablet.

You really need to have good outlet and charger

[ksks]

Thanks for the replies. I couldn't find much info on electrical noise but I'm guessing it could potentially damage a device?
It's an official Samsung charger that I've been using on a range of devices so I'm surprised, but definitely won't be using it again. If only the Lumi 2 wasn't so eye-wateringly expensive, I wouldn't be so worried!

[Arjava]

That problem shouldn't have happened if Onyx was using good parts...