The solar cells should generate 44mA at 1000W/m2. At a nearby (20km away) weather station solar radiation is 600-800W/m2. So now I should expect 60-80% of 44mA solar current. I measured solar panel (2 cells in series) voltage is 0.95V. Now I can calculated the expected battery charge current. 

700/1000 W/m2 * 44 mA * 0.85 boost efficiency * 0.95 charge efficiency *  4.12V/0.95V = 5.73 mA. 

I actually measured 6.0mA. This means that the battery charge current is as expected.

In full sun power (1000W/m2) I expect 8.19mA charge current. Some time soon I want to measure indoor charge current to confirm it is about 1/100th of outdoor charge current.