Bose Soundlike Mini 1 problem: red LED flashing

Hello everyone, I'm having trouble with my Bose Soundlike Mini 1. I used it, and the next day it wouldn't turn on. So I put it on charge, and now the battery light is flashing rapidly in red. When I plug it in, Bluetooth connects, and it starts flashing red again. I should mention that I'm not using the original charger, and it's always worked before. Thanks for your help
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If yours is several years old and used regularly, the rechargeable batteries are most likely worn out.

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