Radio does not send properly when battery-powered

[vikingl]

Hallo mysensors community!

I am totally new to everything here but slowly making my way through the various posts on how to build sensors properly!

My goal is to build battery-powered window sensors!
My setup: 3,3v Mini Pro 8Mhz, nrf-radios, serial-gateway with arduino nano hooked to a raspberry pi with home assistant running!

My problem:
I´ve build a sensor based on the circuit from @petewill shown here: https://forum.mysensors.org/topic/6734/video-how-to-battery-powered-chair-occupancy-contact-sensor and the example binary-sensor sketch in the arduino mysesnsors library.
When my 3,3v mini pro is still hooked to my pc via usb and ftdi-adapter, it works perfectly fine! I change the switch, the mini pro reacts instantly, sends a signal, the gateway leds green and yellow blink once and the state of the sensor in home-assistant changes within a second.
BUT
when I disconnect my mini pro from my pc and hook it up to the two aa-batteries (like in the circuit above) the whole process just refuses to work.
When I change the switch in battery mode absolutely nothing happens! But sometimes, like every 30 seconds or so, the mini pro just lights up, sends something, and the gateway-leds green and yellow blink multiple times. This is completely different to the usb-powered mode!
Also, the changed state of the switch is not transmitted to home-assistant within this automatic, untriggered, sending-phase!

I don´t think it is a range-issue, since I am still having sensor and gateway right next to each other on my table.
I´ve tried putting a 47 uF capacitor between vcc and gnd of the radio, too.

So what could I do? I definitely need your help here!
Thank you all in advance! Looking forward to your answers!

[skywatch]

@vikingl Interesting issue.

1. Is your node wired exactly like the example you link to? You didn't connect the batteries to raw instead of vcc by any chance?

2. Try moving the node and gateway further apart. Sometimes being too close can have negative effect.

3. Are you using new batteries of good quality? Are battery connections secure?

[petewill]

Maybe you need to update the bootloader and/or fuses? Maybe it has a brownout setting of 4.3V?

http://www.ladyada.net/learn/avr/fuses.html

[electrik]

Is your voltage regulator powerful enough?
Could you try a bigger capacitor?