Lucent Technologies KS-20472 - Measure Specific Gravity; Guidelines

Lucent Technologies Round Cell Batteries
7 - 18 Operation and Maintenance Issue 3 December 1999
Measure Specific Gravity
Guidelines Measuring specific gravity as a regular maintenance routine is not
required for the Round Cell. Specific gravity readings are recommended
only when problems arise. Before measuring the specific gravity of any
of the cells, review the safety admonishments and precautions in Section
4, Safety.
• The correct specific gravity of the electrolyte used in Round Cell
Batteries is 1.215 ±0.005. The electrolyte is the same sulfuric acid
normally used in lead-acid batteries.
• Take specific gravity readings before rather than after adding water.
This is because the water and electrolyte do not mix completely for
some time. After water is added, the Round Cells on float charge will
regain full charge specific gravity in approximately 10 weeks.
• After a discharge, specific gravity readings continue to read low even
after the cells are fully recharged at float charge voltage. Recharge at
float voltage does not generate sufficient amounts of gas to mix the
electrolyte quickly and, consequently, low specific gravity readings
will be obtained temporarily. In approximately 10 weeks, the
electrolyte throughout the cell will have mixed sufficiently to give
accurate specific gravity readings.
• Electrolyte specific gravity readings vary inversely with temperature.
The nominal reading is 1.215 ±0.005 at 77°F (25°C). Some
thermometers have a built-in correction scale to show the equivalent
specific gravity reading at each temperature. If no correcting
thermometer is available, calculate the correct specific gravity by
adding 1 point (0.001) to the hydrometer reading for each 3 degrees
Fahrenheit (1.67 degrees Celsius) that the electrolyte is above 77°F
(25°C) or by subtracting 1 point (0.001) from the hydrometer reading
for each 3 degrees Fahrenheit (1.67 degrees Celsius) that the
electrolyte is below 77°F (25°C).
Note
To avoid electrolyte contamination, hydrometers used in
lead-calcium or lead-antimony cells should not be used in the
Round Cell.