looking at other people’s chart I think this is just as is expected. (except for the sudden jump in voltage) It might charge higher then 2.57 volts, but it quickly drops to 2.57, after which the discharge rate is a lot lower, and it should take a few days to get to 2.45
There is no sudden jump in voltage though that is what the graph shows. Someone else here shared a similar graph, with a spike to near full charge in 45 minutes. I was fooled by that but it is some sort of software error I believe. Don’t know if it has been reported? I have not done so yet. And maybe the charging performance in nominal, I cannot say using only my experience. I just know it takes more than 10 hours of full sunlight to get a full charge under most circumstances. Not the 4 hours of >350W/m2 suggested in FAQs.
My handwritten observations:
I am in Orlando FL. My Tempest has good exposure to the sky for at least six hours per day.
We are in the summer rainy season with clouds and thunderstorms almost every afternoon.
The Tempest has been losing voltage and at 2.33 volts went offline. 4 hours of direct morning sun got it up to 2.34 volts.
Seems the solar charging system is inadequate if it cannot keep up the battery voltage in Florida.
The behavior at low voltage may be normal by design but subpar nonetheless. Brand new Tempest should be able to maintain an acceptable battery voltage when in the open in central Florida.
As replied in other thread, indeed not normal, open a support ticket and customer support will help you by eventually sending you a new unit (free of charge). We can’t do anything more on forum.