Sennheiser Set 810 Notice D'emploi page 28

Charging the battery
Place the receiver into the transmitter's
charging compartment, with the operating
control at the front. The left LED on the
transmitter must light up.
Charge the battery for 24 hours before you use
it for the first time. The normal charging time
is 4-5 hours. A fully charged battery has an
operating time of approx. 4 hours.
Always store the receiver on the transmitter to
ensure that it is fully charged. The transmitter
is automatically turned off by the charging
process. The transmitter automatically
switches to trickle charging so that the battery cannot be overcharged. The
receiver can remain in the charging compartment even when the battery has
been fully charged.
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