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Comment on Measuring Power Draw on a Raspberry Pi

lemmyman@lemmy.world ⁨1⁩ ⁨week⁩ ago

Are you talking about just characterizing one unit one time? How long is “extended?” Do you want time series data or just an average?

For a very simple setup, I’ve used current measurement on a DMM in average mode for ~30 minute durations before.

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Vicinus@piefed.zip ⁨1⁩ ⁨week⁩ ago
Thanks for your thoughts. For your questions:

Yes, this would be likely a one off characterization.

I would like time series data over several days or longer.
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- lemmyman@lemmy.world ⁨1⁩ ⁨week⁩ ago
  A couple suggestions then:
  
  I have a LabJack that I use for things like this. I’d put a sense resistor on the high side, tie that into one of the differential inputs, set up the (admittedly awful) software, and boom I’d have battery voltage and current over time. But that’s several hundred dollars.
  
  Instead of that, you can homebrew a pretty similar thing.
  
  Either use your Pi or a separate Arduino to read voltages. Store it in a file or send it to a host PC over serial every [1-3600] seconds
  
  You could get a module like this one to capture everything digitally
  
  Or you could do it the analog way
  
  Probe battery voltage with an appropriate resistor divider
  
  Probe current with an INA169 or similar
  
  If you are using a BMS, that could give you net power flows in/out of the battery. But you won’t know from that alone whether your solar setup is functioning well or your power draw is low (for example)
  
  For battery state of charge, you could worry about coulomb counting and fancy algorithms. I’d just use voltage. But know battery capacity is not linear with voltage (refer to charge/discharge curves).
  
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