BADU BNR 400 Traduction Du Manuel D'utilisation D'origine page 52

Description
If the battery performance declines, a capacitor guarantees the
maintenance of time for a few minutes during a power cut or
battery replacement. All parameters are saved in a
microprocessor and are therefore retained even without a battery.
Changing the battery:
 Push the battery out towards the front.
 Insert the new battery. "+" pole is on top.
18 EN 01|2020