Battery sizing recommendation?

LTE-M / NB-IoT (Monarch)
1

Hello there,

Would you have any guidance to size the battery properly?

I have my use case in place with amount of data (below 500bytes), frequency at which the data will be sent (4 to 6 times a day), usage of eDRX 327.68s for the majority of the time, usage of PSM during 6 to 8hrs.

Any trick or guidance is welcome!

Thanks,

Brian

2

Dear Brian,

To properly select the size and type of battery, consider the following key factors:

  1. Average Current Consumption
    Take into account the average current, including both sleep (or deep sleep) mode and the active duration of the modem in RX and TX modes — as you’ve already started doing.
    To estimate this value:

Refer to the software release notes, which provide useful data such as average power consumption for: Uplink transmission of 100 bytes using the UDP protocol, 2kB HTTPS transmissions etc…

If your specific scenario is not covered, you can perform your own measurements and extrapolate the expected average consumption.

  1. TX Peak Current Margin
    Ensure that the voltage regulator and battery ESR (Equivalent Series Resistance) can handle transmission peaks.

Peak current values versus temperature are available in the module datasheet.
For example, in Monarch2-GM02S-DataSheet-Rev.22.pdf, refer to Table 31: “Peak Current Measurements”.

  1. Peak Current Buffering
    Use a supercapacitor or a large bulk capacitor to buffer peak currents and stabilize power delivery.

  2. Usage Simulation and Modeling
    Simulate your usage scenario using Excel-based modeling to estimate daily power consumption and size your battery accordingly.

Golden Rule: Always prototype and measure in real-world conditions to validate your Excel-based modeling — lab specifications rarely match actual field drain.