The DuoFern sun sensor 9478-1 is operated exclusively via a battery type CR 2450. The device does not have a solar cell.
A separating foil must be pulled out of the device during initial commissioning.
The service life of the battery is approx. 4 years.
To change the battery, open the device and replace the battery with a new one. The battery is clicked into the rear panel of the device.