Hi!
I require your help regarding a problem I’m encountering.
Description:
I would like to know how long can I use Witty Pi2 regarding power (the battery)
Hardware concerned:
Software concerned:
Troubleshooting steps already taken:
Additional information:
Thank you so much in advance for your help!
A normal Pi2 without any accessories drawing additional current (like a mouse, keyboard etc.), can consume upwards of 1.3 to 1.5A so if you plan to use an external battery to power the Pi, multiply the current draw by the number of hours you want to use it.
If you are referring to the battery which keeps the time, the current draw for the Witty is:
~ 1mA in average with dummy load off (default)
~15mA in average with dummy load on
So when you purchase a CR2032 or CR2025, check the capacity to determine how many hours it can run when drawing 15mA. Keep in mind that you’ll only get up to a % of the full capacity. The big issue is that it’s really hard to find the capacity rating for these batteries. Cheap Chinese variations might only a fraction of the capacity of a name brand (and therefore last only a fraction of the time), but without testing, it’s hard to know.
https://www.pidramble.com/wiki/benchmarks/power-consumption
https://www.robotshop.com/uk/witty-pi-2-rtc--power-management-raspberry-pi-boards.html
Hi cbenson,
Many thanks for your answer which is clear.
My question is about the witty Pi2.
Because, I have already a power supply for the Raspberry over a battery (12v).
So I’ll check it.
The 1mA/15mA static current means the current draw from the power supply when Raspberry Pi is off.
The time keeping current that draw from the CR2032 battery is only 3uA (0.003mA). You can find this value in the specification in the user manual, it is named “Time Keeping Current”. Basically you don’t need to worry about the battery, it can last for years 
