Hello,
I am using the DOIT ESP32 DEVKIT V1. I am trying to power it using an 18650 ranging from 3.3v-4.2v. If I connect battery positive to esp32 3.3v pin and battery negative to esp GND, the board powers up, lights up the on LED, and runs any sketch I have tried so far.
It runs no problem when the battery is at the low end (3.3v) as well as at the high end (4.2v).
I can write a pin high, which then goes to the battery 4.2v, and use this pin to read in other pins high.
My question is why is all of this working? And should I not be doing this? Based on the datasheet and schematic I am surpassing the max voltage on the board as well as the pins, but everything is running fine. I would love to keep this setup, but imagine there is some reason why I should not. Thank you
Power ESP32 through 3.3V Pin
Re: Power ESP32 through 3.3V Pin
The short answer is that the specifications are less "the chip will immediately fail if you exceed this range" and more "the chip will not fail if you keep within this range"...
The chip is probably running hotter than it otherwise would, and it's quite likely its lifespan will be reduced. There may be stability issues as a result of the extra heat. Probably also the usable temperature range is reduced. Some peripherals may not perform to specification.
How much the lifespan is reduced by and what other things may go wrong is an open question: you're off the map now.
How important is your application and how much will you care if it suddenly fails or becomes unstable?
If decide that you want to run within specifications, look for a "very low dropout" 3.3V linear regulator which can handle 500mA current output. This should give you a stable 3.3V across a large range of the battery voltage.
The chip is probably running hotter than it otherwise would, and it's quite likely its lifespan will be reduced. There may be stability issues as a result of the extra heat. Probably also the usable temperature range is reduced. Some peripherals may not perform to specification.
How much the lifespan is reduced by and what other things may go wrong is an open question: you're off the map now.
How important is your application and how much will you care if it suddenly fails or becomes unstable?
If decide that you want to run within specifications, look for a "very low dropout" 3.3V linear regulator which can handle 500mA current output. This should give you a stable 3.3V across a large range of the battery voltage.
Re: Power ESP32 through 3.3V Pin
Thank you so much, that is exactly what I was interested in learning. 
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