Biogents BG-CO2-Timer Mode D'emploi page 47

Battery
The 9 V battery to run the timer is not included in the contents. It has to be
inserted in the back of the body. To run the timer, remove the screws from
the back of the body. Insert a 9 V battery and connect the connection plate
to the battery. Pay attention to connect the battery always with the correct
polarity: hexagonal terminal to round terminal (even a short contact with
the wrong orientation might damage the device). The timer is now switched
on. Then retighten the back of the body with the screws. The charge status
of the battery is shown in the display. The battery should last at least six
months.
47