Battery Life Calculator

#1

I needed to estimate the battery life for a project so created this sheet. It seems to give results that are reflected in the real world tests in respect to the power consumption.

Feel free to give it a try and let me know if you spot any errors of if i have missed anything.

You enter in the Battery Capacity in my case I am using a set of cells that are rated at 4800mAh

Sleep Current is how much power the CubeCell pulls while its in sleep mode. I shut the power off to my sensors using VEXT so I just have the CubeCell in sleep mode.

In my case I read the sensors 380 time per hour, and the sensors and CubeCell when not in transmit mode seem to pull 14.3ma.

And I transmit the data twice per hour unless there is an alert that needs to be dealt with. transmissions seem to be on average about 105ma.

What I have not taken in to account is the self discharge rate of the battery. I can not say at this stage how accurate the estimation it so do not rely on the figures.

#2

I try to this link: Power Consumption testing but I measured a current 7.8 mA during sleep mode. I want to know are you transmit on lorawan or lora transmitted. Now, I think my code have problem, Please shared your source code of this project.

Thank you

#3

My units are connecting to a LoRa gateway set up a forwarder and they only send transmissions.
When i turn on the units i make sure they are not connected to the USB as if you have the USB connected then the USB chip stays active and consumes more power. Also all of the print and serial functions are turned off or removed.

My coder is prety much the same as the low power example in respect to the transmissions with the exception of adding a routine to read the sensors.

I have never found multi-meters to be very good at sensing low current. at the moment i am waiting for a columb counter so i can confirm the power usage. however last night when i fired up the test unit the battery’s were charged to 4.186V and after 7 hours of operating the battery voltage has dropped to 4.184v and that is with one transmission every minute.

#4

If you have a simple app which does nothing apart from sending a transmission every minute, you should be able to measure the sleep current and then calculate the overall power consumption.
In my case I have several other things happening at various times and a PIR sensor, so I found a coulomb counter useful.

1 Like