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Tympan / Tympan_Rev_E_Hardware

Repository for Tympan Rev E Electronics and case designs
MIT License
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Size RTC battery #13

Closed eyuan-creare closed 3 years ago

eyuan-creare commented 3 years ago

The RTC on the Teensy4.1 is integrated on the micro, which the datasheet says requires (20uA). image

However the Teensy 3.6 was measured to draw 2uA, while the datasheet suggests 1uA. Paul believed this additional current was diode leakage, so let's assume 21uA for the Teensy 4.1: https://forum.pjrc.com/threads/45399-Shutdown-RTC-current

The existing CR1220 is 35mAH, which provides a life expectancy of 66days:

Not very impressive. But I believe this would only be the case if the main lithium battery was depleted.


We could go down to two 6mm coin cells (2*1.5V * 20mAh), but there were no holders for two stacked 6mm coin cells.
eyuan-creare commented 3 years ago

@chipaudette Reducing the coin cell appears to be a dead end. I have not measured actual Teensy 4.1 current draw, but from the spec sheet, the CR1220 should last ~66days.