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Understanding the Sensor Battery Display in iMonnit

Keywords: battery, power, battery life, battery percentage


Summary:

Explanation of how the battery life is displayed in the sensor history and the meaning of it.



Many of the Monnit sensor products have multiple power options, for use in different environments. 

  • Monnit commercial coin cell sensors are our least expensive and most common wireless sensors. They are powered by a CR2032 lithium-ion battery and have 250mA hours of energy.
  • Monnit commercial AA sensors are powered by two AA lithium-ion batteries and provide the user with 3,000 mA hours of energy. 
  • Industrial Sensors have the Tadiran battery which is a .36V Lithium battery with 1200 mA hours of energy.
  • The Solar Sensors have a rechargeable 3.2V Lithium Ion Polymer battery and has a capacity of 700mA.

The battery graphic in Monnit's software solutions (iMonnit, Monnit Express and Monnit Enterprise) is represented by five different images:

  • Above 75% it shows Full
  • Above 50% it shows Three Quarters
  • Above 25% it shows Half
  • Above 10% it shows One Quarter
  • Above 0% it shows red
  • At or below 0% it shows Empty

The percentages are configured per the following table:

 Sensor Battery Chart

Monnit uses linear interpolation for all values between the given points. For example, a battery voltage of 2.95 is between 2.9 and 3.0. The battery percent is half way between 75% and 100% (or 87.5%) so the display will be rounded to 88%. When you hover your mouse above the battery icon, a small text box pops up and that value is displayed:

 Battery Hover in iMonnit

Because the power reservoir is small in the CR2032, the voltage can fluctuate between reads. This can cause the reading to change from 50% to 0% by only having a .15V drop at the time of the battery read. For example, if the network encounters any interference and the sensor has to transmit more than once, the battery will display lower than subsequent readings that didn't have to send retries.

A benefit to the other battery choices is that they will show a much smoother curve as the batteries drain due to the larger power reservoir.



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