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Battery Power Options

Home Forums Mayfly Data Logger Battery Power Options

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This topic contains 11 replies, has 5 voices, and was last updated by  Sara Damiano 1 week, 3 days ago.

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  • #1806

    Marion
    Participant

    Can the Mayfly be powered by a 4.5 volt alkaline battery pack? For a monitoring station under a bridge or in deep shade this would be an low cost option to supply power for long term logging where solar recharging is not feasible. The borad schematic shows a voltage regulator (SPX 3819) connected to the LiPo battery connectors which appears to be capable of handling the 4.5 volt input.

  • #1812

    Shannon Hicks
    Keymaster

    Yes, you could attach a 4.5v alkaline battery pack to the LIPO battery connection, but since you never know who might come along later and plug a solar panel into the SOLAR jack, it’s good practice to only connect LIPO batteries to that jack. That’s why I designed a separate 2-pin header (unpopulated) on the Mayfly that’s labeled “Ext 5V” so you can solder a little 2-pin header (preferably polarized) on there and connect an external battery pack that way. I like this particular connector/header combo: https://www.allelectronics.com/item/con-242/2-pin-connector-w/header-.10/1.html

  • #1854

    Bert Rubash
    Participant

    I have a related question. Why should I not plug two LIPO batteries to the battery jacks. Is it because I would risk too much charging current? If I refrain from charging, wouldn’t having two batteries plugged in simply extend operating time?

  • #1856

    Shannon Hicks
    Keymaster

    The charging circuitry on the Mayfly isn’t capable of charging 2 parallel battery packs simultaneously, so it’s not advised to connect two packs to the Mayfly if you ever connect a mucroUSB cable or solar panel to it because either of those will start the charging process.

    The second LIPO connector on the Mayfly is for providing a direct connection to the battery for high-current accessories like a GPRSbee module. It’s not supposed to be used to provide a secondary battery input for the Mayfly.

    However, if you take precautions to make sure you never connect a microUSB or solar panel, then theoretically it’s possible to connect two parallel batteries to power the Mayfly, but you run into the usual issues related to parallel battery operation, like making sure both batteries have identical capacity and are charged to the same initial voltage, along with other precautions. Given the dangers of short-circuiting LIPO batteries and causing a fire, EnviroDIY does not recommend that users connect more than one battery to their Mayfly at a time.

    Also, if you connected 2 LIPO batteries at once, you can’t use the onboard LIPO charging circuitry on the Mayfly, so there’s no benefit to using LIPO batteries and you might as well just use a single high-capacity battery pack of a different chemistry (like lead acid or alkaline) if you’re looking for longer lifespan.

  • #1857

    Bert Rubash
    Participant

    Thanks, I’ll avoid plugging in two LIPO batteries.

  • #12843

    Cal
    Participant

    I’m planning to replace some existing datalogging equipment with the Mayfly and keep some of the existing power equipment.

    Today I have several stations each with Campbell Scientific dataloggers & sensors, standalone modems, solar panels, lead-acid batteries and charging circuits. The equipment is all 12v based. My desire is to pull out the dataloggers and modems and replace them with Mayflies + Digi modem modules. I have all the software working which includes interfacing the CS pressure transducers and cellular communications.

    The question is: can I use/keep the existing power (12v 8aH battery, 24v solar panel and charging circuit) and how should I connect to the Mayfly? Also – do I need a LiPo battery to supply the modem?

    Thanks for any ideas/help. – Cal

  • #12845

    Sara Damiano
    Moderator

    Depending on the version of the Mayfly you have, there’s a 12V power input that you can step down and use. If I remember correctly, though, @aufdenkampe once told me he’d had smoother power and less loss using a separate 12V to USB step down and powering the Mayfly via the USB port.

    Unfortunately, though, with either option you would still need a LiPo to supply the modem. The Digi cellular modems require more amperage than the Mayfly can provide on its own so the only option is to power them directly off the battery by way of SJ13. If you don’t have a battery plugged into one of the Mayfly’s battery jacks, the modem wouldn’t be powered at all.

  • #12848

    Cal
    Participant

    Thanks Sara. I think a cheap 12v to 5v phone charger will work well for me then.
    As for the LiPo battery – I will use a small one. Our transmissions are short and the LiPo will be recharged from the lead-acid battery.

    I have the V0.5b version of the Mayfly – so I could use the 12v input. But I’m a little worried though that the voltage may spike above 14v during sunny days. Do you think that would be a problem?

    I have a small disagreement with your last comment: “the modem wouldn’t be powered at all”. I often run my Mayfly + Digi modem WITHOUT a battery! It works (most of the time) so it does get power from my USB source – but I know it’s on the edge. I have the SJ13 soldered.

    Cal

    • #12850

      Shannon Hicks
      Keymaster

      The Mayfly can handle up to 16v input without risk of blowing anything up. I designed it that way so people can power it with a 12v battery that’s also attached to a charger, so their battery sees up to 15v sometimes, but still won’t hurt the Mayfly.

  • #12849

    Sara Damiano
    Moderator

    Oops, yes, sorry, the modem would have power without the battery, just not enough. The naked u-blox SARA R410 cellular chip uses just barely under half an amp at peak. (Assuming you’re using the LTE model.) Add the Digi processor and it’s too much. I’ve never had any luck getting it to connect without a battery. It browns out and stops responding. Often it needs to be completely powered off (or yanked from the board) before it will be happy again.

    I think @acgold might have gotten the Sodaq SARA R410 uBee working with the Mayfly without the solder jumper: https://github.com/EnviroDIY/ModularSensors/issues/228

  • #12853

    Sara Damiano
    Moderator

    Hopefully @aufdenkampe will confirm but I think he went the USB route mainly to avoid power losses in the step down. If you go that way you probably need a relatively expensive 12V to USB to make sure you are getting less loss than the built in step down.

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