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Primary powering in cold settings

Home Forums Infrastructure and Equipment Primary powering in cold settings

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    • #17286
      neilh20
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      Following from the post @dysumner https://www.envirodiy.org/topic/mayfly-v1-1-technical-questions-forum-thread/#post-17284
      I thought I would share some data that I’ve got from running a Mayfly on non-rechargeable Primary Battery outside.
      Batteries are electro-chemical reactions and temperature does affect them. I chose 3.6V ‘D’ LiSOCL2 ~ 12Ahr@0C, 19Ahr@20C,as its specified to -30C https://www.evebatteryusa.com/lisocl2-specifications

      So far I think I have a test station that has been running 18months – basic details here
      https://github.com/neilh10/ModularSensors/wiki/Stream-Disconnect-EC-Monitor
      It is of course the simplest of sensors ~ a simple ElectricalConductivity measurement.
      I’ve made Mayfly 0.5 measurements – Assuming all switches set to the lowest settings for Mayfly1.1 should be as good.
      Sleep/Quiescent – target 0.5mA ~ though I also have measurements 1.2mA to 2.0mA while sleeping
      Running ~ 16mA ~ 20mA

      As well as collecting all power usage ratings, I would suggest you look at what powering subsystem can work at a toasty adiabatic (for the artic) 1C.
      One side effect of the LiSocl2 is it has a high internal impedance – so need to consider what current demand happens when turning on sensors – and that becomes more of a problem as it gets to the end of its life – so adding some smoothing might be extend its life – http://www.gebc-energy.com/en-US/Product-99.html The Mayfly has minimal powerline capacitance.
      As an extension of the EC sensor, I mentored some Elec Eng students with final year project by adding an LTE transmitter. The purpose of it was for them to consider the power demand. They created a simple spread sheet, I can share if its of interest.

      IMHO the Mayfly doesn’t do specifications – there is a lot of description, but I have had to dig into the schematic and device specifications to get a better understanding of the powering subsystem. The benefit of open source. The Mayfly1.1 has much better defined devices LDO overheads, and 3.6V is at the edge of working, but is probably ok as the battery discharges to about 3.4V. The processor mega1284 works down to 2.7V. Using the Mayfly battery voltage measurement is challenging and I’ve blogged extensively elsewhere about that.
      How the atlas sensors take current could be challenging – and require a good super capacitor buffer, possibly 10F which are lo-cost – https://www.whiteboxes.ch/docs/tentacle/t1-mkII/#/power?id=power-consumption

      So for powering you may want to share what your thoughts are for working at 1C.

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