Powering Pico with a coin cell

Posted on
  • Title says all...
    I'm planning to use a CR2032 coin cell, I read that the Espruino accepts 3.5V-16V but I just want to ask, will 3V work, or is it too less? I know it sounds like a stupid question but I just wanted to make sure.

  • Sat 2018.09.01

    'I know it sounds like a stupid question'

    The only stupid questions are the ones not asked.

    @Marty_McFly ambitious, aren't we!

    While your intentions are admirable, checking the datasheet and the Pico specs will give you that answer. The following is the analysis process one should go through.

    Datasheet

    http://data.energizer.com/pdfs/cr2032.pd­f

    One can tell at a glance from the table that the voltage drops off considerably with higher current draw.

    Device

    As you also verified, and also under heading 'Battery'

    http://www.espruino.com/Pico

    'This means that it will run off of normal 3.7v LiPo batteries (or any voltage up to 16v).'

    Analysis

    My understanding is that the Pico was to draw power from the USB port at 5v, and also stand alone LiPo battery 3.7v. In the design then, was a voltage regulator for the microcontroller, that also requires a slightly higher voltage in order to supply steady state 3.3V This then would require a supply voltage slightly more than 3.3v. That would prevent the CR2032 from being a power source choice. I think you realized that.

    What other components do you intend to power at the same time?

    Alternatives

    Looking up Alkaline CR2032 now . . . .


    EDIT
    Lithium 3v and Alkaline seem to be available at 1.5v only

    https://www.h-squared.co.uk/single-use-b­utton-and-coin-cells

  • Don't know your space constraints, but 3 Alkaline (LRs - or simple 3 AAA) may be a better solution... you could even think of 3 (rechargeable) NiMHn s. If you really want to go for button cells, there are rechargeable CR2032 that deliver 3.6V - more than the regular which deliver only 3V - but they have a fraction - 20% - of the capacity: rechargeable CR2032. They give you 40mAH,... putting a few in parallel could be an option - feeding PICO on VBAT pin.

    Espruino Power Consumption shows you what you need... if it is to just keep something going with very very very low duty cycle, you may get away with a single 40mAh cell... but be aware, that when Pico runs, it is draws very very very heavy on the cell... 10...100 times more the load as most shown discharge profiles even document the capacity for... which means that it may run, may be - it is a guess - 20 mins continuously... That's why now the newer, even more lower power chips are available and aree
    used for BLE... may be you change to a BLE breakout (or pixl for that reason).

  • As other have said, the Pico's 'peak' power consumption is really just too much for a standard CR2032. You could use a supercapacitor in parallel if you wanted, and that would make things work ok.

    The Pico's processor will run down to around 2v, so the voltage isn't too much of an issue even with the regulator's ~0.3v voltage drop. It's just the stuff you want to connect the Pico to that might complain!

    Do you have to use a Pico? The MDBT42 Breakout would happily run off a coin cell for quite a while.

    If you really want to go for button cells, there are rechargeable CR2032 that deliver 3.6V

    I've actually tried these and they work great with the Pico - but as @allObjects says you don't get much capacity out of them

  • Post a reply
    • Bold
    • Italics
    • Link
    • Image
    • List
    • Quote
    • code
    • Preview
About

Powering Pico with a coin cell

Posted by Avatar for Marty_McFly @Marty_McFly

Actions