While I was waiting on the new PCB to come in, I started testing the charging of the battery under real conditions. What I did was take just the daughter board from the old design (as shown above) and force the path from the solar panel through the LT1085 to the battery. Then about once a day I recorded the battery voltage to see what was happening. The data so far is shown here.
There were some very sunny days and a few slightly clouded days. In retrospect, I probably should have recorded the sky conditions for the previous period also. The data shows how the voltage has varied. As a reminder, the solar panel is only 7.5W and has a max current of about 500mA, under ideal sun conditions. Given the time of year and the fact that sun does not clear the house next door until after 11AM this time of year, I am not surprised that it is not charging very fast. Once the house next door is not blocking the sun at anytime, which won't happen until sometime in March, I suspect it will be hard to charge much faster.
I am surprised that there appears to be some discharge during the night. It is not much and for now I am assuming it is more self discharge due to very cold nights (20-25F). There might be some sneak current path back into the LT1085 when it is not powered. I did put in a diode in the new desig to help prevent this.
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