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lifepo4 solar system

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    • 2022-10-20 at 6:06 AM #17406
      Dave
      Participant

        Hi all

         

        Just wanted to get your thoughts or options for lifepo4 power for monitoring stations. First off, I generally use an arduino pro mini 3.3V for switching on/off the main logging system and in sleep mode the pro mini consumes ~50 uA. I’ve also just got a hold of the rocket stream mini ultra which promises 4 uA sleep current, lets see about that! That said, with logging frequencies of 2-5 minutes using 2/3G communications, I still end up with rather large solar panels!

        Temperature range here is usually <20 degrees C, very occasionally dipping below -5 deg C.

        For my remote projects I’m currently using a li-ion / solar battery system off the shelf:

        https://www.solartechnology.co.uk/category/hubi/hubi-go/

        These are ok, but a bit bulky, I think the charger / battery box is largely empty space. I put it in a steel vented enclosure just in case the batteries were to catch fire – overkill?

        Pros: off the shelf / CE rated, not too expensive

        Cons: bulky, hard to scale down, li-ion batteries can go on fire

        I’d really like to experiment with lifepo4 (single or two cell setup, say 5,000 – 10,000 mAh), due to the safety benefits compared to li-ion, and the increased number of charging cycles.

        Ideally, I would like to find a single module that would take care of charging, under-voltage protection and solar input from a solar panel. The closest I could find was the mikroe charger 11 click (https://www.mikroe.com/charger-11-click) – but it doesn’t come with a solar input, and I think it uses a proprietary compiler – it would be nice if adafruit made such a board!

        Just wondered if anyone has implemented their own lifepo4 solar systems?

         

        Thanks!

         

         

         

         

         

         

         

         

      • 2022-10-21 at 7:24 PM #17407
        neilh20
        Participant

          @davem great topic.  I was at a SSU Eng Presentation yesterday by Enphase   a leading solar equipment provider and they use LiPo4 in their battery 3.3Kwh/10Kwh systems.  All about safety.  LiPo4 slightly less power density — but that isn’t a problem with stationary systems.  No temperature stability. Fire issues are a big deal. A recent newspaper report on a local house fire referenced a device that had been left on charge and caught fire.

          I’ve got some largish PO4 tube batteries designed for electric bikes.  However the challenge is as you point out is different charging regime and management.  At the present my guess it can be a system block at 5V or 12V.  However it would be nice for SBC (single board computers) like the Mayfly to have the LiPO4 interface.   I seemdd to remember Rocket used to with SAMD21 LoRa + LiPO4

          There was also a rPi powering system that used LiP04 – I think this is,

          https://hackaday.io/project/13260-lifepo4weredsolar1

          One way of minimizing power consumption with fast sampling is to queue the reading,  and then upload every 4-12hours, which is what I do, but is a lot of software work. When I have some time I plan to post it for the Mayfly, but haven’t heard a lot of people asking for it.

          Also to minimize cellular power, use a cloud host that can encode the data and suck the data up fast. However subscriptions are quite costly. So great topic 🙂

        • 2022-10-25 at 9:50 AM #17410
          Dave
          Participant

            Thanks for the feedback

            Funny you should mention rocket scream, I’ve just had a few red comet esp32s delivered. They promise low power consumption and solar charging for lifepo4. I’m hoping to replace a rather bulky 12V panel and battery system with the red comet and a single cell 26650 lifepo4 (see picture).

            Red Comet ESP32

            I’ll use the red comet to read simple interrupts from a couple of flow sensors, and a separate MKR1400 will do the communications at 12/hr or daily intervals as you have mentioned. This is all in theory…lets see how it works in practice. One thing I haven’t researched much is power monitoring. I believe due to the flat discharge curve of lifepo4, you need to use a coulomb counter? Another day’s work..

            Btw I’m backing a lifepo4 product on kickstarter for home energy harvesting (4.6 kWh) also using lifepo4 batteries. Very similar to enphase by the looks of it. The safety aspect, plus having an EV socket clinched it…

             

            Attachments:

            1. 5V-solar-scaled.jpg

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