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Institute of Electrical and Electronics Engineers

THE ARC LIGHTVol. 1, No.2

Apr. 1995

A publication provided by Power Engineering, Inc., to share information regarding methods and procedures available for maintenance and testing of electrical generation, storage and distribution systems.

In our previous newsletter we discussed the importance of maintenance and testing for your UPS, telecommunications or switchgear battery in general terms. We shall now address the specifics for inspection and maintenance.

GENERAL

All inspections should be performed under normal float conditions where possible. Measurements should be performed as per the manufacturer's written instructions. Regular inspections should include visual checks for signs of cracks in the cell/unit or electrolyte leakage, unusual jar or cover distortion, signs of corrosion at terminal connections or racks/cabinets, and ambient temperature/ventilation. The inspection should also include a review of the general appearance/cleanliness of the battery installation and accessibility to emergency wash and spill containment materials.

Electrical measurements should be recorded on a Monthly, Quarterly and Annual basis. Monthly readings should include Overall float voltage (measured at the battery terminals), pilot cell readings and charger output voltage and current. Quarterly readings should include the monthly readings, float voltage of each cell and electrolyte temperature of every sixth cell. For a valve regulated lead acid (VRLA) battery, record the negative post temperature. Annual measurements should include the Quarterly readings , Intercell and internal cell resistance of each cell/unit.

FLOODED CELL

The visual inspection of a Flooded battery installation should include a record of the electrolyte level of each cell. In the case of three tier racks or Lead Antimony cells, this should be monitored regularly. Adding water to the electrolyte0 is an important maintenance requirement in stationary battery systems. The electrolyte solution should not go above the High level mark and care should be taken not to allow the level to drop below the Low level mark. The electrolyte level should never be allowed to drop to a point that can expose the plate material to air. Only approved water should be added to the electrolyte. In addition to the procedure recommended for all batteries, specific gravities should be recorded for each cell in the battery on an annual basis

Flooded cells out perform VRLA cells due to the relatively low internal resistance. Internal resistance is the leading factor in the load performance of VRLA cells. A recently adopted ANSI/IEEE standard, IEEE 1188, addresses the importance of regular Impedance testing. Internal cell measurements should be recorded as part of the Quarterly Inspection. AC ripple current and voltage should be recorded on acceptance and as part of the Annual measurements.

The only sure way to determine the condition of a battery is through load testing (ex. capacity testing). This is the only method to simulate the actual operating conditions of the battery . In addition to Acceptance testing, Performance or Capacity testing should be performed on an annual basis until the battery shows signs of degradation.

It is vital that benchmark data be established for the battery at the time of commissioning. This data can be used for comparison with information collected during each subsequent procedure in the outlined maintenance schedules.