Sony SRS-X2 - Manual (Page 45)

Note
Charge the speaker while it is turned off. You cannot charge the speaker while it is turned on.
When you switch the power source between the USB AC adaptor and the battery by connecting/disconnecting the
USB AC adaptor, the speaker may stop sound output for a short while in rare cases. This is not a malfunction.
The maximum power output will be lower when the USB AC adaptor is disconnected.
In an extremely cold or hot environment, charging may end prematurely or may not be possible. This is not
malfunction.
Even if you do not intend to use the speaker for a long time, charge the battery to its full capacity once every 6
months to maintain its performance.
Related Topic
Turning the power on
Notes on charging
Notes on use
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