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Problem with battery drain

Has anyone had a problem with batteries dying very quickly?

When I put my first module together I didn't have any jumper wires, so I just turned it on and off a couple times and put it away, but I'm sure the power jumper was removed. The next day I switched it on and it already showed the flashing led for low battery. By the next day the battery was completely dead, but I had put it in new, straight from the package and had only switched the module on a few times without ever playing it. I thought maybe it was just a bad battery, but I put together the rest of my modules today and one was showing low battery within a few hours and I had only played with it for maybe half an hour.
What could be causing this high discharge? I checked all my solder joints carefully and there was nothing wrong, although I had nothing to clean the flux from my first module when I soldered it. Could this really lead to such a high rate of self discharge?
For now I'm removing the batteries when the minimos aren't in use. When I get back to my own workspace I'll probably set them up with their own power supply, but I'm curious what's going on anyway. I hope to get a multimeter this week and make some tests.


  • edited May 2018

    hi! was that battery completely discharged, as in, the module wouldn't turn on?

    I put the battery check in place as a means to know which modules have fresh batteries on them, but it's not an indication that you must change the battery right away - the modules should run fine much longer after you see the multiple flashes. It's more of an indication that if the modules are not performing as expected, you could try a fresh battery -for instance, if you're programming the module from an Arduino, running the module on battery, and the program repeatedly fails to load, or if you're running a sequencer with an oscillator and the frequencies start drifting. The ultimate indication that the battery is too low is a very faint light on the LED and the program completely misbehaving.

    Maybe I should change the wording in the manual to reflect what I just wrote. I could also change the programs so that two blinks mean "battery not fresh" and many blinks mean "really low".

    Other than that, I don't see how the modules could discharge if you have the jumper set to ext, as the battery is disconnected from the circuit. However, note that the modules don't have a "standby" mode, so if they're ON they will be draining the battery regardless of what you do.

    Let me know what you think! also, if you get ahold of a multimeter, it would be useful to see what's the voltage in your batteries, both new and "low".

  • I think I shorted that first battery badly on the minus terminal, I may have left it at an angle, shorted and that's why it died completely. It's at 1.9v and won't power a module on at all. I noticed because I took one out to test it and the voltage was rebounding from 2.8 and returned almost to 3.1. But all the other batteries are completely fine and holding charge normally. Maybe it's possible that leaving uncleaned flux on the pcb was responsible for something, but it seems like a lot? I'm still a beginner with this stuff. Anyway, I cleaned the flux before i ran the voltage tests so too late to know.
    I'm still at a stage of electronics where I often don't know where to begin checking what mistakes I've made :D
    But having lots of fun with the modules now.
    On an unrelated note, I noticed that the power jumper and potentiometer knob fit nicely in the bottom half of the case for traveling! Cool feature
  • edited May 2018

    It's at 1.9v and won't power a module on at all.

    The chip inside miniMO works from 1.8V, so that's expected.

    If you post here (or send me) pictures of the boards, I can give them a look and tell you if I see anything out of the ordinary; at least you will know if everything's OK now.

    On an unrelated note, I noticed that the power jumper and potentiometer knob fit nicely in the bottom half of the case for traveling! Cool feature

    Thanks for the tip! It never occurred to me to use the case for storage :P

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