Hey everyone! I’ve been diving into the world of MQTT and battery monitoring, and I wanted to share my experiences and some tips that might help others who are exploring this as well. 
So, I started by setting up OwnTracks on my Android phone to track my battery level using the guide from Home Assistant. It worked like a charm at first—battery values came through and updated in real-time. But then I noticed something odd: if my phone wasn’t connected, the battery value would disappear, leaving just a blank space with a percentage sign. 
After some research, I found out that this is a common issue when devices go offline. The good news is there’s a workaround! By tweaking the MQTT configuration, you can set the battery sensor to retain its last value until it’s updated again. This means you won’t lose track of your battery level even when your phone isn’t connected. 
Here’s how I did it:
- Enable Retain in MQTT: Make sure the MQTT broker is set to retain messages. This ensures that the last known battery value is stored and available even when the device is offline.
- Adjust Sensor Settings: Modify the sensor configuration in Home Assistant to use the retained value. This way, the battery level remains visible until the device reconnects and sends a new update.
- Test and Monitor: After making these changes, test the setup by disconnecting your device and observing if the battery value remains consistent.
This tweak has been a lifesaver for me, especially when I’m out and about and don’t want to worry about my device’s battery status. It’s also a great example of how a little bit of tweaking can make a big difference in how your smart home works for you. 
If anyone else has tips or tricks for MQTT battery monitoring, I’d love to hear them! Let’s keep the conversation going and help each other optimize our setups. 