pytrack / pysense supply through normal alkaline batteries

  • If the lopy is used as a standalone module in my applications, one of its most interesting features concerns its flexibility regarding the values ​​of the supply voltage, which can be in the range from 3.3V to 5.5V.
    For some applications I intend to use a logger consisting of a lopy together with one of your expansion boards (pysense, pytrack or expansion board). For the power supply of the logger I would like to use 3 alkaline batteries (therefore not rechargeable) connected to the JST connector of the lipo battery. For the type of application I am not interested in using rechargeable batteries.
    The lipo batteries have a nominal voltage of 3.7V, but when fully charged the voltage reaches 4.2V.
    The three batteries in series provide a nominal voltage of 4.5V, but if the batteries are fully charged the voltage can exceed 4.8V.
    is the power management circuitry through the JST connector of the lipo battery able to withstand a voltage level that can reach up to 4.8V?
    Best regards.
    Marco Rainone

  • Don't know about the lopy. On the pysense they have a BQ24040 charger, which has a maximum battery voltage of 7 V (see datasheet). As jcaron wrote, alkaline cells have significant internal impedance, which is increasing with discharge and lower temperature. Watch the battery holders, the popular conical spring coil ones are crap. Maybe add a supercap to buffer current pulses from the RF transmitter.

  • @mrainone don’t have the answer to your question, but note:

    • beware than if anyone connects the device via USB it will start charging the batteries. Not good, at all.

    • beyond voltage, one needs to check the instantaneous current the batteries can provide (the LoPy has quite a few spikes during the awake cycle). No idea if alkaline batteries can withstand that, you’ll need to check.

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