Dakota looking through the refractometer
The true measure of a battery state of charge is the specific gravity value. As you can see on this page, a fully charged battery should be 1.265. We made a chart and measured the specific gravity of the electrolyte of each cell in all 13 batteries. We used an instrument called a refractometer to do the testing. We are trying to determine if we have any batteries or cells that read lower than the others. Readings should not vary more than .05 differences between cells. So far, so good. We have a couple of batteries that are "suspect" right now and we may have to desulfate them and recheck later. We did find last week that we had one battery with a dead cell, so we replaced it and things are looking better for now.
P.S. I bribed the students with doughnuts to get them to work!!