Hallo Hubert,
yes I am from Germany - You can use the youtube-subtitle to change it into English ;-)
It depends on Using the DM-24.
In my DM-24 I use the battery about 20 Years - and after changing the old battery it had anyway an Voltage about 3V. Nevertheless, I changed it - because i have open the Device for change 1 Fader from an other Mixer ;-)
Stefan