I purchased the phantom 4 last weekend. The RC battery came 1/2 charged. I tried to fully charge it but the LEDs go out after 5 seconds and the remote beeps every 3 seconds. The charger does charge the aircraft batteries fully.

I found a past post that recommended "re syncing" the controller. I did that and it responded as was stated in the post, but no difference in the remotes battery.

I did post a service ticket, but alas it's Sunday.

Any other thoughts? Probably just a defective RC battery.

The 'beep' may indicate that you need to recalibrate the sticks as it is probably warning you that the throttle is not at the center point.

Try starting the charge process with the controller turned off, does it still fail to charge?

Does sound like one battery has failed.  I think the controller has two 3.7 volt batteries and runs on maybe 7.4 volts with them being in series.  Does sound like it has to go in unless you can go for an exchange.

Fwiw, while paying my cell phone bill I asked about a new phone.  They were sold out which seemed odd.  The guy said "They don't order many even if it's popular because if the thing sits and the battery dies inside it, they cannot activate the SIM card system and test it and then have to return the phone.  When some of the older models had removable batteries they could slide a shop battery in and get it going, or put a boost or reactivate charge on the one pulled out if it was dead."  Thought it sounded like the drone's battery system with its dead batteries from sitting too long on a store shelf.  Maybe DJI needs a "Sell by date" on the box.  

Sorry to hear about the remote issue.
Just to clarify, the charger is working fine and battery can be charged properly, right?
Would you please provide us a video showing that?
If the battery is defective, we'd love to help you handle it soon.

I have the same problem with my RC and have opened a repair ticket.  Do you know if the charger tags along for evaluation or just the RC?