Re-calibrate the battery ADC with the battery capacity.

For PV1 and DV2 main battery
4.2v 891 99%
4.10v 870 97%
4.05v 859 92%
4.00v 848 86%
3.95v 838 82%
3.90v 827 76%
3.85v 817 68%
3.80v 806 59%
3.75v 795 47%
3.70v 785 31%
3.67v 778 21%
3.647v 773 15%
3.62v 767 10%
3.60v 763 7% go to sleep
3.55v 753 5%
3.50v 742 4%

Secondary Battery
4.2v 880 100%
4.1v 861 99%
4.05v 851 98%
4.00v 840 96%
3.95v 830 88%
3.90v 819 84%
3.85v 806 79%
3.80v 798 71%
3.75v 786 63%
3.70v 774 54%
3.65v 765 37%

battery low at 781.