Why Battery Level Varies in Monnit Sensors

Why Battery Level Varies in Monnit ALTA Sensors

Many users ask why they see their battery levels, which are reported by sensors, vary. A wandering battery level is not necessarily a sign of a battery issue. How frequently ALTA Sensors measure battery level can result in inconsistent readings.

How Battery Level is Reported

1. Monnit Sensors take a sample of the battery voltage to interpret the battery level. The relation between the battery voltage and the percent reported in iMonnit can be reviewed in this article. 
2. The battery's voltage in your sensor is sampled during the sensor Heartbeat while the sensor’s radio is active. When the sensor’s radio is active, the battery is under the heaviest load it will experience.
3. As a result, the battery level can vary quite a bit while it is under load; thus, the battery level reported in the software will reflect this.

Why Monnit Measures Battery Voltage While it is Under Load

The stable nominal voltage of a battery, while not under load, is generally much higher than the voltage while it is under load. Therefore, if you measure the battery while it is not under load, you may get the impression the battery's health is in better shape than it is.

This is why Monnit measures the battery voltage under load, as it gives a more accurate representation of the battery's condition. While it does mean that the battery level reported on different Heartbeats may vary, the overall picture of the battery health is more accurate.

The Larger Picture

This is normal behavior if your ALTA Sensor's battery level varies between Heartbeats. Rather than focusing on a single battery level report, looking at the battery level reported over a more extended period will give you a more accurate picture of the battery performance.

Effects of Radio Environment, Temperature, and Usage

A noisy radio environment and the ambient temperature in which the battery operates can affect the battery level, especially while it is under load. Therefore, if your sensors operate within a refrigerator or freezer or are in a noisy radio environment (or have a low signal due to distance from the gateway), you might see this reflected in the battery level reported by the sensor.

Also, the more frequently your sensor’s radio is active, the less time the battery has to recover from being under load. Therefore, heavier usage (more frequent Heartbeats) can exponentially affect the battery level. The battery may be depleted more rapidly, and the reported battery level may be inconsistent and varied.

Differences between Gen1 and ALTA

Generation 1 (Commercial) sensors did not measure batteries in this manner. This was introduced in our ALTA line to provide a more accurate picture of the battery performance. This is why you may have Generation 1 sensors that have more stable battery performance when compared to ALTA. 

However, this is not a result of actual differences in battery performance but rather the method (It's more accurate with the ALTA Sensors) by which the battery level is measured.

Conclusion

While the battery level variance is common, other issues may indicate a problem with the battery or sensor. If you have questions about this, feel free to contact support@monnit.com.