I had the same thing happen. The audiologist blamed the batteries; the battery company blamed the aids. I sent them back to Phonak for repair and they no longer beep. There was no indication of what was wrong with them though, just the standard “replaced electronics.”
However, once I got them back, I had a new problem – one of them often wouldn’t boot up when I closed the battery door. I wound up having to send it back again, which was maddening. I’m unimpressed with Phonak’s quality control.