Sony MDR-1RBT - Manual (Page 30)

Charging starts when the headset and the computer are connected.
Make sure that the indicator (red) lights up. Charging is completed in about
6 hours* and the indicator (red) goes off automatically.
* Time required to charge the empty battery to its full capacity
Notes
If the headset is not used for a long time, the indicator (red) may not light up
when you connect the micro-USB cable to charge the headset. In this case, do
not disconnect the micro-USB cable from the headset and wait until the indicator
(red) lights up.
When you close the cover of the micro-USB port after charging the battery, push
the catch at the edge (the round part) of the cover into the port compartment.
Catch
Tips
If the micro-USB cable is connected to a computer while the headset is turned
on, the headset will be turned off automatically.
To charge the headset from an AC outlet, use USB Charging AC Power
Adaptor* (sold separately). For details, refer to the manuals supplied with the
USB Charging AC Power Adaptor.
The headset cannot be turned on while charging the battery.
* Refer to the Reference Guide on the recommended adapter.
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