after investigation we’ve discovered that we had a bug in latest battery-modules released binary which was not powering down the Core Module. Also when the module is not sleeping then the DC/DC chip was running constantly and you heard the continuous buzzing noise.
Please update Core Module to the lastest 1.7.2 firmware. If you use dongle, please update also this firmware to 1.7.2 and update the gateway bcg. We’ve fixed some issues with pairing.
Please try it and let us know if the noise issue went away. These high-frequency noises can be eliminated also by our enclosures. You can download and 3D print or buy them in our shop.
Here are some general tips that I’ve written just before I’ve heard about that bug in generic-firmware. I think it is still relevant so I keep that here:
Also the red LED turns on for a second when you first power-up the Core Module. The blinking is probably because the voltage is so low, that the Core Module is randomly reseting in the loop.
The generic-node firmware is created in a way, that the data are send periodically every few minutes, but if the value changes rapidly, then it is send immediately. This works fine for temperature, pressure and humidity, but you’ve mentioned that you also have the luxmeter. It is possible that the illuminance in the place where you put the Core Module was changing very often and has been send wirelessly every few seconds and drain the battery after a shorter time than usual.
If you really want to have running Core Module on batteries as long as possible - the best solution is to create your own firmware based on generic firmware source code and set the period of sending the data to the minimum and maybe disable the code which sends the values immediatelly when they change rapidly.