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How to make a NiMh battery setup
First, I would reccomend a 100 µF capacitor , preferably elecroyctic, for a drop in electrical voltage can occur in NiMh due to the electric resistance inside the battery. the opposite of a LiPo or Li-Ion spike in voltage.
also, something to bear in mind is that NiMh run at a slightly lower voltagethen alkalines, 1.2V rather than 1.5V. that means a 3S setup (3 series) will have an output of 3.6V at fully charged and 3.0V when it is a "safe empty".
so, how to connect your NiMh to a Pico. First of all, remember that capacitor? wire the input of it to the positive terminal (Positive voltage) of your batteries. Then, wire the output to the Pico's VSYS, which accepts a voltage of 1.8V-5.5V. then, wire the negative terminal (if you want it to always run, wire the Ground to the negative terminal of the batteries (usually Ground, or 0V)) through a slideswitch and then, connect the slide switch output to the Negative terminal (sometimes referred to as ground, 0V) of the battery setup.
Now, how to monitor the battery voltage?
I reccomend you wire voltage from the capacitor straight to an ADC pin, where you can create code to flip an SR latch (or latching relay) and thenbreak the circuit when the current is too low.(I reccomend a CMOS MOSFET SR latch, because it wil consume almost no power when idle)
End of tutorial
