Sony MDR-AS700BT Help Manual page 29

Make sure that you connect the plug of the micro-USB cable in the direction as
shown in the illustration below.
Charging starts when the headset and the computer are connected.
Make sure that the indicator (red) lights up. Charging is completed in about
1.5 hours* and the indicator (red) goes off automatically.
* Time required to charge the empty battery to its full capacity
Notes
Use the micro-USB cable supplied. You may not be able to charge the headset
with other cables.
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.
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 AC Adaptor* (sold
separately). For details, refer to the manuals supplied with the USB AC Adaptor.
The headset cannot be turned on while charging the battery.
* Refer to the Reference Guide on the recommended adapter.
Caution
If the headset detects a problem while charging, the indicator (red) may turn off,
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