Trouble Conditions; Post Connections; Positive Plate Growth - Nortel DMS-100 Series Maintenance Manual

3–26 Power system maintenance

3.8.2 Trouble conditions

Routinely evaluate the condition of each battery in the battery plant to
determine if any maintenance action is required.
The following paragraphs describe the trouble conditions of lead-calcium
and lead-antimony cells and batteries. The most common troubles with
lead-calcium and lead-antimony cells are loose battery post connections,
positive plate growth, battery post corrosion, and problems related to low
electrolyte levels and high ambient temperatures.

3.8.3 Post connections

Loose battery post connections can result in high-resistance contacts. The
high resistance can cause the connection to heat excessively, which can
damage cable insulation and battery post bushings.
Any loose battery post connections must be tightened to the manufacturer's
specification. A torque wrench should be used to check the tightness of the
battery post connections.

3.8.4 Positive plate growth

Positive plate growth is the expansion of the positive battery plate caused by
oxidation of the lead, which causes the lead to change to lead dioxide. Lead
dioxide occupies more volume than lead, resulting in lead plate expansion.
The problems resulting from positive plate growth can be seen by examining
the construction of the battery as shown in Figure 3–15. As the positive
plate expands, it eventually makes contact with the cell jar and begins to
exert pressure on the jar wall. With further expansion, the battery jar bulges
under the stress, and the force on the jar wall builds to the point where the
cell jar cracks (Figure 3–16). The cracks in the cell jar then permit the
battery electrolyte to escape.
Positive plate growth can progress enough to cause cell jar failure before the
expected cell life of 20 years is reached. Regularly check any lead-calcium
and lead-antimony cells that are 10 years old or older for signs of positive
plate growth.
Positive plate growth is visible in transparent containers and may be gauged
by eye. A cutaway view of the battery plates may be seen in Figure 3–16.
Only positive plates are expected to grow. In new batteries, the positive
297-1001-350 Standard 02.02 August 1997
DANGER
Battery hazard
When using metallic tools on batteries, take great care to avoid
possible personnel injury and equipment damage. Always use
insulated tools on battery equipment.