I’ve used a XIAO combined with other electronics with a 12V battery, dropping the voltage to 5.0V with a 7805 regulator and because the XIAO itself draws relatively low current I put a diode to drop the voltage by 0.6V to about 4.4V, connected to pin 13 - the 5V pin, so it doesn’t compete with the USB. The internal conversion seems happy with this headroom. When the USB is connected its supplying the power, when removed the XIAO is powered from the 4.4V.
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