In the Billy app, open up Settings 
and click Sensor Status.
On this screen, you'll see the current battery state and it will tell you whether the sensor is online or offline.
What do the battery symbols mean?
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The battery is full. | |
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The battery is no longer full, but there is no need to replace just yet. | |
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The battery is low. To avoid any disruption to your service, please replace the battery. | |
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The battery is low and the sensor is now offline. No activity will be reported by the sensor while it is offline. Please replace the battery. You can find more information here: What batteries do the Billy sensors use? | |
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The sensor is offline. For tips on how to get this online, check out our help centre article here: What do I do if my sensor is offline? |