Specific Gravity, Checking

Specific Gravity, Checking

Special tools, test equipment and auxiliary items







- Commercially available hydrometer
- Shop towel


CAUTION!
- When working with battery acid, make sure to follow all "Warnings and safety precautions for lead-acid batteries. " Wear suitable protective clothing and eye protection.
- When disposing of batteries, always comply with applicable Federal, State and local laws regarding the disposal of batteries and sulfuric acid.


NOTE:
- In order to better determine the overall condition of a battery, always perform a specific gravity test in conjunction with the load test.
- The temperature of the electrolyte must be at least 10 °C (50 °F).


The specific gravity can be tested immediately after charging the battery.
Use the following procedure to test the specific gravity in all of the battery cells:
- Switch ignition off.
- Remove all cell caps.







- Immerse tip of hydrometer into battery cell and draw out enough electrolyte to allow indicator to float freely.

The higher the specific gravity of the drawn electrolyte, the higher the indicator will float.

The specific gravity of the electrolyte can be read in kg/cubic dm on the hydrometer scale.

- Compare measured value indicated on hydrometer to values indicated in table below:

State of charge in Specific gravity in
normal climate zones kg/cubic dm
Discharged 1.12
Half charged 1.20
Good charge 1.28

In normal climate zones, the specific gravity must be at least 1.24 kg/cubic dm.

- If specific gravity is too low: charge battery.
- After charging battery, repeat specific gravity test.


NOTE: The measured values for the specific gravity of the individual battery cells must not vary by more than 0.03 kg/cubic dm.


Examples of unacceptable variations in specific gravity:







- If values are not met, replace battery.
- If values are met, reinstall cell caps.

The original cell caps that came with the battery must be reinstalled to help prevent leakage.
If the cell caps are lost or damaged, use replacement cell caps of the same manufacture.
The cell caps must be equipped with an O-ring seal.