Battery Gauges and Instruments for Testing
Every set of Delco-Light batteries has either one or two cells equipped with a pilot ball. Such a cell is known as a PILOT CELL. Fig. 294.
Pilot Cells are used to indicate to the USER the approximate state of charge or discharge of the battery.
The pilot ball is a battery gauge which is UP or DOWN, depending upon the state of charge of the battery.
Very high temperature affects the operation of the pilot ball. This accounts for-the fact that occasionally a battery will be charged and the pilot ball will be at the bottom of the pocket. A few hours later, after the electrolyte has cooled, the pilot ball will rise to the top.
We urge that the user be made to feel that the pilot ball is an excellent gauge and a good signal to watch in connection with the care and operation of his Delco-Light plant and battery. (Further mention will be made of the pilot ball in connection with the subject of proper operation.)
It is necessary that the maximum specific gravity of pilot cells be as near 1.220 as possible. Any great variation higher or lower will affect the operation of the pilot balls. Therefore, every effort should be made to adjust the maximum specific gravity of pilot cells to 1.220 when placed in service.
Batteries equipped with one pilot cell contain a white pilot ball which will be up when the specific gravity of the electrolyte is approximately 1.185. This ball will drop DOWN when the specific gravity falls a little below 1.185.
In other words, the pilot ball will float at a specific gravity of 1:185 or higher, and will sink at a specific gravity lower than 1.185.
Therefore, when the pilot ball is UP, the battery is more than half charged. When the pilot ball is DOWN, the battery is more than half discharged.
Batteries equipped with two pilot cells have one cell which contains a white ball and the other cell a white ball with a blue band.
The plain white ball will be UP when the specific gravity is approximately 1.175. The blue band ball will be UP when the specific gravity is approximately 1.205.
When both balls are UP, the battery is charged. When DOWN, the battery is discharged. The blue band ball will drop soon after the battery starts on discharge, or, in other words, when the specific gravity falls below 1.205. The white ball will remain UP until the specific gravity falls below 1.175.