I have a Xeeed ESP32S3 that runs on a Li-Ion battery on the Vbat connection. I also have an external voltage source that fluctuates between 14 and 20 V DC and that I can convert to 5V with an MP1584EN. This allows me to power the Xeeed via the USB-C connection. The problem is: that external voltage source suffers from frequent short interruptions. Frequent interruptions of 5 to 50 mil sec, and regular interruptions of 30 to 600 sec. I think this is not so good for the xeeed ESP32s3. Can’t the board be set up to run on battery and use the 5 V from the USB-C supply only for the charging circuit? As far as I know, the XEEED ESP32S3 always gives priority to the 5V supply from the USB input. Can’t it be set to give priority to the battery and use the 5V only for the charging circuit? This board will be built into a small toy car, where there is almost no room for additional hardware.
You can use LM2576 as a step-down regulator.
Set the LM2576 to step down your fluctuating 14–20V input to a stable 5V output.
Use a proper inductor (typically 100 µH for 5V output) and capacitors as specified in the datasheet.
Add a capacitor at the input (100 µF–470 µF) and output (470 µF or higher) to stabilize the circuit against interruptions.
Place a Schottky diode across the input to protect against reverse polarity.
Hi there,
So as @liaifat85 points out the step down is the way to go here, Also just to add IF your pulling High current for short period with S3 you need that BIG capacitor next to the 5V in.
for some reason I find it’s easily browned out and resets under those conditions. just FYI
the Converter may also provide some with the 470uF part.
HTH
GL 
PJ 