On a freshly charged 18650 I was seeing values around 4.1-4.2V when checking battery status on WisBlock API with a RAK4631 - while the battery was not charging.
On the same device, I moved it to using RUI3 (installed the RUI3 firmware, changed the code), but now I am getting values around 3.9V on a fully charged 18650.
Why is it so much lower? Is there a reference voltage discrepancy I need to account for somewhere, or something like that?
EDIT: I will say that I did not put a multimeter on the battery to see what it said…I’ll check when I get time.
I am checking battery like this in my RUI3 code:
uint16_t batt = (uint16_t)(api.system.bat.get() * 1000); // Battery in mV