V3.9 : the charging LED is always on

V3.9 : I did not connect the USB cable ,but the charging LED was still on .
re-stalled the battery or reset , still the same .
Thank you .

My OS version is 7.8 .

If you mean the green LED on the Proffieboard itself, that’s a status LED, and on this page you can see what it’s showing:

If you mean some other other LED, that would be something different.