The sound on these is great and I love them freedom of the bluetooth

The sound on these is great and I love them freedom of the bluetooth, but I am having an issue with these charging. I charged them completely the first time and everything seemed fine. Every time after that the headphones only seem to charge 1/3 of the way according to the display on the iPhone 7 I am pairing them with. The indicators on each bud turn blue, but after about 1/2 hour of use I get the verbal low battery indicator and the headphones shut down after another 5 minutes.

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