The 2-ball is also used for automotive applications but most often marine batteries. It will provide a bright green indication if the battery is charged, a dark indication when partially discharged, red when fully discharged and a clear and bright indication if the electrolyte level is low.
A two ball battery indicator displays three distinct stages of a battery's condition.
1Green dot visible (OK)
2Dark green dot not visible (charge before testing)
3Light or yellow (replace battery)
