4-30. STORAGE BATTERIES, CONNECTIONS, AND BATTERY COMPARTMENT (cont)
Before making test, open electrical equipment cabinet door and set battery switch to OPEN. Clean battery as
Remove corrosion on connector bolts, lugs, and cables by washing with water/soda solution (1 pound
bicarbonate of soda to 1 gallon of water).
Rinse with clean water and allow to air dry.
Remove vent caps and clean out the vents in the cap.
Check the specific gravity as follows:
Place the hydrometer in a cell and remove enough electrolyte to fill the barrel of the syringe to a level
which will permit the hydrometer to float freely without touching the barrel at either top or bottom. Allow
the rubber bulb to expand completely and hold syringe by the neck of the bulb.
Shake the syringe gently to be sure hydrometer is floating freely.
Hold the syringe at eye level.
Record the indication at the point at which the electrolyte level appears to intersect the stem of the
The fully charged specific gravity varies in different types of batteries and is shown on the battery
nameplate. Readings should register in the vicinity of 1280 points.
The discharged specific gravity (not shown on the battery nameplate) also varies with battery type
but is usually around 130 to 140 points lower than the fully charged specific gravity.
A specific gravity reading 100 points below the full charge value is a warning of either battery or
charging problems. A specific gravity reading between cells of the same battery that differs more
than 20 points may indicate a dead cell.
Add distilled water to 1/8 inch (3.2 mm) below the bottom of the filling tube in the cover.
Check the tightness of the connector bolts and apply a thin coating of petrolatum. Wipe off excess with a clean