I see the dev boards use a .22F super cap for the RTC. What is the expected hold over time with the size cap?
This is something we have to test further, but initial testing has shown that the supercap should power the RTC for at least a week.
Anyone out there want to put it to the test?
first question… how long does it take to get the cap to full charge?
Another good question
My guess is ~18mins to 63% and ~91mins for 100%
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How did you determine those numbers? Datasheet?
Licked my finger and stuck it in the air 
Ah, a SWAG.
So how is the best way to test? Any reboot to check the time will re-charge the capacitor. Measuring the voltage will start to drain the capacitor.
Lol, not quite as wild as normal … Assuming the register GHI has set then its 5RC so R is either 5k or 1.5k depending on said register from the St datasheet. I guessed they are setting the 5k register hence my high end space time continume calculation.
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Ah… the old tau