Smart Controller only 4 months old.  I've charged it for 14 hours and it's still only 75 % charged.  I'm using the original DJI charger and cable.
I've tried other cables and other chargers.  All give the same warning that charging is slow and to use the original DJI Charger.
Charging is so slow that if I turn it on, the battery drains.

Hello there Electromen. I am sorry for the trouble this has caused and thank you for reaching out. May we know what is the firmware version of your device? Did you try to charge it when the DJI Smart Controller is turned off completely? It usually takes about 2 hours to fully charge a DJI Smart Controller with the provided charger. If a third-party charger is used, the charger needs to support QC2.0 or higher charging protocol. Thank you.

DJI Stephen Posted at 12-30 21:20
Hello there Electromen. I am sorry for the trouble this has caused and thank you for reaching out. May we know what is the firmware version of your device? Did you try to charge it when the DJI Smart Controller is turned off completely? It usually takes about 2 hours to fully charge a DJI Smart Controller with the provided charger. If a third-party charger is used, the charger needs to support QC2.0 or higher charging protocol. Thank you.

I'm using the DJI charger and cable that came with the SC. Yes, the SC was turned off during charging.   When I woke up this morning the SC was 100%.   I turned it on until it reached 97% and plugged it in.  Again I received the message : "Current charging speed slow.  Please use the charger that comes with the device for a faster charging speed."
System Version 1.0.86.0

I just finished Refreshing the firmware of the SC using DJI Assistant 2.
It still does the same thing.

Electromen Posted at 2020-12-31 11:22
I'm using the DJI charger and cable that came with the SC. Yes, the SC was turned off during charging.   When I woke up this morning the SC was 100%.   I turned it on until it reached 97% and plugged it in.  Again I received the message : "Current charging speed slow.  Please use the charger that comes with the device for a faster charging speed."
System Version 1.0.86.0

Hi there Electromen. Thank you for the reply and for the information you have given. Since this issue is still happening. I would recommended for you to contact our DJI Support team at ( https://www.dji.com/support ) for us to be able to check the said remote controller and the proper resolution will be provided. Again, I am sorry for the trouble this has caused and thank you for your understanding.