After more than three years, the battery “suddenly” swelled up. But, “this music will last forever if I replace the batteries.” As I wrote earlier, batteries from Zopo ZP980 / C2 are suitable, of which I have a great many in a state of alert. He requisitioned half of his daughter's eraser (cut into two parts by thickness), he didn’t even have to cut in length. And everything got up and working wonderfully.
Real 2000 mAh is certainly worse than 2800, but much better than nothing, including aliexpress.