After some days of cloudy weather, the LiPo cell voltage of my second Airnote (a replacement) dropped for the first time down to 3.5 V and the device stopped transmitting data. Hence I connected the Airnote’s USB port to a Samsung cell phone wall-plug charger, an EP-TA20EWE .
The day after, Grafana’s dashboard showed that the voltage had increased up to the abnormally high value of 4.9 V, the same problem I wrote about in a previous post dealing with my original device (see “Issues with USB charging of Airnote’s battery”, September 21st, 2021). I removed the USB supply and the monitored voltage settled down to 4.19 V, a normal value for a 3.7 V fully loaded cell. Please refer to the attached screen capture.
These questions arise:
a) Are the dangerously high values of the battery voltage during the charge periods just an artifact of the monitoring circuit?
b) How reliable are Grafana’s voltage readings?
c) Is it safe to keep the 5 V USB supply continuously connected to the Airnote?
Thank you very much and best regards,