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Can anyone find any specs on how long the battery lasts?

The ESP32 is a pretty serious power hog...

ESP's only a power hog when it's using the WiFi... In deep sleep it can go as low as 10 uA! .15mA gets you the low-power processor for doing sensor interrupts.

In reality Watchy currently draws around 1mA while sleeping and 55 hours of battery for me, not using WiFi (not really a priority for me).. I think that can be improved with firmware updates, seems like there is potentially some low-hanging fruit. It's all open source firmware, so you can eg. program it to deep sleep while you deep sleep to save battery :)

That is a power hog, compared to say an STM32L4 with, per spec, ~250 nA deep sleep w/ RTC & some RAM (to make it at least somewhat comparable to the ESP) and 50uA/MHz dynamic run mode.

Also you shouldn't just take steady state values. I've had various ESP's on a power analyzer. They take a bit more (like 30mA for many msec? iirc) for a while during wake up (w/ wifi off) before the consumption drops to the final value. For example some of that goes into uncontrolled/undocumented oscillations on some pins (for up to 100ms?), thought that is probably a negligible part.

ESP's are only popular because they're the cheapest/easiest option with WiFi. At least that's why I use them...

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