Some useful info I had tucked away The chart above shows the battery charged after sitting for a few hours. This is called a surface charge, it is about 1 percent plus or minus of the total after fully charged reading of 12.75 volts. You can remove a surface charge by turning on the headlights with a volt meter hooked up to the battery, the volts will drop but any thing under 10 volts and dropping will indicate a bad cell or two= bad battery