Sennheiser MX W1 Instruction Manual page 20

Replacing the earphones' rechargeable batteries
Danger of damage to the devices!
CAUTION!
Rechargeable
manufacturers may cause damage to the
earphones and will invalidate the warranty.
Slightly lift the end of the caps and slide the caps out of the
guide rails.
Insert the new rechargeable batteries as shown. Observe
correct polarity when inserting the batteries.
Replace the caps
it clicks audibly.
Charge the earphones until the corresponding LEDs go off
(see page 8).
18
button
Only use original Sennheiser rechargeable
button cells (see page 22).
and slide them onto the guide rails until
cells from other