Bangle.js 2 Battery won’t exceed 94% + ghosting

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  • I received my Bangle.js 2 last night, assembled the straps and plugged in with the charge cable. It charged up to 94% really fast, but no matter how long I left it charging I couldn’t get it past 94%.

    The cable is plugged the right way, as per the instructions card in the box.

    On a non-related issue, the screen seems to have a ghosting issue when I change application. I suspect it might just be refresh frequency, but I’m unsure. One of the settings labelled “Beep” reads ‘undefined’. Whenever I select it the whole watch crashes. Is this just a software issue?


  • Hi,

    I wouldn't be too concerned about the battery percentage - it's kind of an estimate based on battery voltage, which depends on temperature as well as the calibration value of some resistors - I'd be pretty sure your battery is still fully charged. If you could run analogRead(D3) when your Bangle is fully charged (but off charge) and tell me the result, I'll update the values so the next firmware reads ok.

    And sorry about the Beep issue. Yes, It's just software - I just checked it and while I'd made some Bangle.js 2 tweaks there it seems it had some hard-coded pin values that it attempts to use to make a beep sound (left from Bangle.js 1) - when it poked that hardware pin it caused a crash. I'll get a fix in now

  • Hey Gordon,

    analogRead(D3) returned =0.314453125. Pin D3 didn't show anything in the docs, what does it correspond to?
    Is this an issue all Bangle.js 2 have, or just this one?
    Also, is there a way to fix the screen-ghosting issue?

    Thanks again.

  • I see, thank you for showing me this.

  • D3 is the actual physical pin on the IC that the battery voltage pin is connected to.

    The voltage varies between devices, yours isn't broken or anything - basically if you order a 100k resistor, you never actually get 100k - it's always +/- some threshold (usually 10%). To make matters worst the manufacturers sell the +/- 1%, 2%, 5% for a premium so you're basically guaranteed that a 100k resistor is either less than 95k or more than 105k.

    So when there's a potential divider in the watch sometimes you can get unlucky and one resistor is really high, one is really low, and it just pushes the reported voltage out. I had checked a few watches when coming up with the range but because the default battery widget doesn't display a percent I probably wouldn't have noticed after I'd done it if some were out.

    As for ghosting - I will get a software fix in for this soon, but realistically not until next week earliest.

  • Hey again, thanks for helping me so far, you've been brilliant.

    Assuming I did get ~10% less supply voltage, how can I fix it? I don't want to always see <94% on the display and I remember from an earlier thread that opening it up to change the resistors in question is not an option, as there are no screws like in my Bangle 1.

    What can I do?

  • Literally all you need to do is update the firmware and it'll fix it in software.

    The voltage is just just for the battery measurements, so the fact it's off by a bit changes nothing apart from the battery percent indicator

  • Another data point for fiddling with the firmware:
    (It won't go over 68% charged)

  • I've just added this to Settings so in a day or so you'll be able to go to Settings -> Utils -> Calibrate battery when the Bangle has been on charge and it'll reset the battery percentage meter

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Bangle.js 2 Battery won’t exceed 94% + ghosting

Posted by Avatar for Asynchronous @Asynchronous