We are developing an end device based on CMWX1ZZABZ-091 for measuring environmental parameters.
Does anyone have experience in dimensioning batteries for the CMWX1ZZABZ-091?
It consumes around 2uA (measured on the ST’s EVM) in deep sleep plus the current peaks in the transmission. The consumption of the sensors is negligible.
What would be the adequate capacity for a range of 3/5 years with an hourly message?
Four out of the first five entries look useful:
You have the hardware, and the code, so measure it.
Most everyone else would be guessing.
A low value resistor in series with the device power will when used with a scope give you the current profile, so then all you need to do is the sums.
There a straight forward way to measure power consumption.
What uses the battery power is the project doing stuff. Reading sensors, transmiting LoRa packets. Thats what really makes your battery go flat.
If your project does an hourly update, you can speed up the use of battery by a factor of 240 if you send the payload every 15 seconds say. You can screen the project in a metal box so you dont exceed fair access limits etc.
If you use a small lithium battery of say 100mA, thats around 1/10th the capacity of a pack of AAA batteries.
So now your node is using power at 2,400 times the rate versus a pack of AAAs with an hourly update. If the projects battery life was expected to be 5 years then under this test regime the 100mAhr battery needs to last … 18hours. Not difficult to test ?
Once you know how many maHr each transmission uses, you can factor in the deep sleep current and work out what the projected battery lfe would be.
I started a test at the end of last year, using a sensor node with a small battery to see how much power the node would really use. The battery was a 155mAhr Lipo the node a bare bones ATmega328P using the watchdog timer to sleep for 15minutes and send the LoRa payload @ 14dBm, fairly typical of a TTN node maybe. The 155mAhr battery has fallen from 4218mV to 3928mV in 5 months, the projected battery life is currently over 2 years. Details here;