Lowbat - warning Homematic HM-CC-RT-DN


I’m using homeassistant with debmatic. Unfortunately I can’t use the plug-in, because it is not working.
As hardware I have the HM-MOD-RPI-PCB.
Home Assistant detected, the debmatic and created for each HM-CC-RT-DN (thermostat) two entities. One climate entity and a “lowbat” binary sensor entity. Now the debmatic announced, that one of the thermostats has a low battery on channel 4. I expected, that the lowbat-sensor would tell it to me. But it didn’t happen. I waited until i got a valve error (so the battery is really empty now). But there is still no reaction from the lowbat-sensor. Is the sensor not connected to to battery-warning on channel 4? And where is it getting its information from?

Thanks for your help,