tl;dr If an encrypted phone is decrypted while charging, the battery LED will keeps on, even after disconnecting charging cable/change setting/soft reboot.
Device: Samsung Galaxy S4 LTE (GT-I9505) running CM13 snapshot 20160820
I have wiped the system+data+cache partitions of my S4 and flashed CM13 rom. Default setting is to have battery LED on while charging. I disabled this in Settings. No LED on during charging. That's what I want.
Then I set up device encryption (Settings -> Security -> Encrypt Phone). Afterwards, I disconnected the charger, reboot, and enter my password to decrypt the phone. Then I connected the charger again. Still no LED on. (Normal)
Then I reboot the device again. Before decrypting the phone I connected it to charger. The battery LED is now on with green colour. I guess it's due to my settings being encrypted, and the default of "LED on while charging" is applied.
But when I decrypted my phone while charging, the LED keeps on even after the lock screen is shown, or when it is unlocked to launcher. I disconnected the charger, putting the device in non-charging status. The battery LED is still on with green light without charging.
I tried repeatedly (dis)connecting charger, turning LED on/off in Settings, and even soft reboot. The charging LED still shines on. The only way I managed to get the LED off is to shutdown/regular reboot the device.
Further experiment shows that this problem appears only when I press enter (after entering password) to decrypt my phone while charging. The phone is normal (LED off) if I enter my password while charging, disconnect the charger, and press enter to decrypt the phone.
Question: Is there any way to decrypt the phone while charging, and still keep the battery LED off?