Originally Posted by veloso
I bought a MHL Adapter (microUSB - HDMI) from DealExterme .
It works well, even without power, but when I put the original charger (2A), the S4 starts charging but can't even hold the charge. The charge will slowly dropping over time.
Is this normal?
 MHL to HDMI Adapter Cable for Samsung Galaxy S3 i9300 / S4 i9500 / Note II N7100 - Red + Black ($9.40)
Firstly, I don't have an S4, but I do have a Note 2 which also comes with a 2A charger. In my experience when using an MHL adapter the phone will only charge very slowly at best. If you are making it work hard, the battery will slowly drain. If I understand correctly, this is because of a limitation regarding how much power a normal USB port can supply.
When your phone is connected to a wall charger, go into settings and 'more' and tap 'battery'. At the top it should tell you it's charging, and that the type is A/C. Now plug in your MHL adapter, and plug the charger into the MHL adapter and go back into the same settings page - on my Note 2 (and also my HTC Sensation), this page now shows 'USB' instead of A/C. If the same is true with the S4 (and I'm pretty sure it will be), this is the source of the problem. It wouldn't matter if the charger was 1A, 2A or even more, the phone will only draw so much from what it thinks is a USB port. It's a pain, but there you go.
When you connect your phone to a TV via MHL, try lowering the screen brightness on the phone to minimum manually. If you have a quick search, there's also an app on here that should allow you to power of the S4's screen completely and still allow you to output a picture to the TV. Sorry, I don't have the link to hand.