Lesson 2/Learning Event 2
The electrolyte should be at the correct level in the cell. Water in the electrolyte evaporates; the
acid does not. If the water has evaporated enough so the electrolyte level is low, the mixture will
be strong and the gravity reading will be high. On the other hand, if the battery has been overfilled
with water, the electrolyte will be weakened and the reading will be low.
When water is added, it will tend to remain at the top of the cell, and you should not test
immediately after adding water. If water must to be added before a reading, the battery should be
charged for one to two hours to mix the electrolyte before the optical battery/antifreeze tester is
Gravity readings will not tell the true state of the electrolyte just after a battery has been discharged
at a high rate (such as just after the engine has been cranked for a long time). In this case, the
acid has been used up next to the plates but the electrolyte near the top of the plates is still strong.
The optical battery/antifreeze tester will read a higher state of charge than actually exists. The
electrolyte will show a true reading if the battery is allowed to stand unused for several hours or if
it is charged for one to two hours.
MEASURING SPECIFIC GRAVITYWITH THE OPTICAL BATTERY/ANTIFREEZE TESTER
This tester is quick, accurate, and reliable. There is no guesswork or arithmetic involved. The
tester automatically adjusts for temperature.
The plastic cover and the measuring window must be clean and dry. Wipe clean with a soft cloth.
Clean the eyepiece lens. Use clean water to clean dirty areas.
Swing the plastic cover down until it rests against the measuring window.
Make a separate test for each battery cell.
Using the black dipstick, place a few drops of electrolyte onto the exposed portion of the measuring