Koss KS5429-2 Manuel Du Propriétaire page 10

2. Charging
A built-in rechargeable battery (Li-Ion) is included for portable use.
A fully charged battery can support about 2 hours of playtime.
When the built-in battery cannot power the unit or is used for the
first time, recharge it.
1) Switch ON/OFF to OFF.
2) Connect the AC adaptor to the DC jack and a standard wall outlet.
The red indicator will light up. Once fully recharged, the red light
will turn off.
3) Disconnect the AC adapter to stop charging.
Note: It usually takes about 5 hours to charge the battery.
Note: Charge the battery for at least 8 hours before you use it for
the first use.
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