I have an ESP32 project that spends most of its time in deep sleep, and almost never turns on the radio. I’d like to power it for a year without changing batteries. And I’d like to use AA or coin cells so I can swap them out easily.
Is there a way to do this with the Thing without attaching an external power regulator to 3V3? The hookup guide warns against putting anything but a lipo on Vbat, and I’m not sure if Vusb can step up voltages.
Related question: is it reasonable to hook the batteries to an ADC pin (probably across a voltage divider to keep it in range) to act as a battery monitor?
The ESP32 Thing uses ~250mA for RF transmissions, which is the max rating of the standard CR2032 battery…even if it almost never uses it, you may experience ‘brown-out’ (unless you have some that are rated higher?)
Is there any reason why you wouldn’t want to just usea small Lipo? They are easily rechargeable - you don’t even need to disconnect them (although having some pre-charged and swapping them would be even easier).
You’d probably want to avoid using the battery socket to save power, but you could connect 2 AA batteries (3 volts) directly to the 3V3 and GND pins and power the board that way. There are a bunch of other things on the board that are going to be getting powered so I don’t know if you can get a year out of a set of batteries but swapping the AA batteries for C or D cells would increase your run time.
The ADC on the ESP32 maxes out at 3.3 volts so you’d be able to connect the battery directly to a ADC input to monitor it’s charge status.
Make sure you remove the batteries when connecting the board to USB for programming or debugging so that you’re not accidentally ‘charging’ non rechargeable batteries. 