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Not the OP, but my understanding (admittedly a few years outdated) is that an MSP430 will, in idle, with sleep states properly set up and low power modes in use, drain a coin cell battery (e.g. CR2032) over a period of years - with the current drawn around 1.5 uA in standby and 0.1uA in RAM retention idle.

That is likely even lower than the effective self discharge rate of a lithium coin cell battery. I don't believe the Arm equivalents like the Cortex M0 can deliver such low absolute current - maybe microamps, but more than an MSP430 from what I can see.

Ref - https://metebalci.com/blog/measuring-the-power-consumption-o...




> That is likely even lower than the effective self discharge rate of a lithium coin cell battery.

That's what I've found too. Based on my measurements and calculations, Photon uses 5µA (MSP430 + motion sensor) while sleeping, while the battery's self-discharge is more like 80µA.

That's probably a good argument for using a more powerful chip though, if the battery self-discharge is that high, hah.


Maybe tiny solar panel + capacitor, like 1980/90s calculators had, then it could run "forever" - digital Millennium Camera.


This is a cool idea!


Or a different battery chemistry with a lower self discharge rate. No need to be rechargable in most of the use cases, I'd imagine.


Panasonic BR2032 has 30µA discharge rate https://www.digikey.com/en/products/detail/panasonic-bsg/BR-...


If that's the self discharge rate then the battery would be fully discharged after less than a year on the shelf (given its 190mAh capacity). Coin cells typically have a much longer shelf life than that. I wonder what that figure is, exactly.


This sounds like a job for a lithium thionyl chloride battery.

The guys with the purple LiSoCl2 batteries make ones with up to 40 years of usable life


Some of the SiLabs EFM32 parts have comparable sleep currents.




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