Could be the charger. Without much information, did you try another charger? A different USB cable? My controllers charges fine on my Nintendo Switch port and my phone charger.
I'm thinking your controller is fine simply because it is charging with the PS4…
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=== Update (01/13/2020) ===
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So I ran a couple of tests with two of my older Samsung charger bricks (one from my old S4 and the other from my Note 10.1 (2012 version). Input is .34A and output is 2A on both. Both chargers charged both of my controllers with no issue. I also ran my rapids charger from my S7 (.5A input and 1.67/2A output) and it charged them fine. Now I also put them on my portable battery packs of 1000mA. No issue.
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Take it as you will, but I had little issue charging my controllers.
Could be the charger. Without much information, did you try another charger? A different USB cable? My controllers charges fine on my Nintendo Switch port and my phone charger.
I'm thinking your controller is fine simply because it is charging with the PS4…