3. BATTERY TESTING 

The purpose of this section is to describe recommended testing procedures and intervals. Information herein consists of guidelines only and is not intended to replace manufacturer’s recommendations. Follow manufacturer’s information if a conflict between these guidelines and manufacturers information is encountered. 

3.1 ACCEPTANCE TESTING

Acceptance testing should be performed no sooner than 1 week after the battery has had its initial freshening charge (see section 1.2 A). This test may be done at the factory before shipping if specified. This test should be at least a 3-hour discharge test and should provide at least 90 percent of rated capacity. An 8-hour discharge test for acceptance is preferred, and 90 percent of rated capacity should be required. 

3.2 CAPACITY TEST TO DETERMINE REPLACEMENT

To establish whether a battery is nearing the end of its useful life, load test the entire battery as outlined below at 5-year intervals. This test should be repeated annually if the capacity has dropped below 90 percent. 

A. A. After the battery has been fully charged by equalizing, return it to float service for at least 72 hours, but less than 30 days before performing the test. 

B. Check all battery connections with a micro-ohmmeter to ensure connections are clean and low resistance. An IR camera may be used just after the discharge test has begun to check the connections. Temperature will be higher on poor connections. If poor connections are found, stop the test and repair the connections before continuing. 

C.    Record the specific gravity and voltage of each cell just prior to the test. 

D. D. Record the temperature of the electrolyte of 10 percent or more of the cells (an IR camera may be used and the temperature of cell cases may be recorded) to establish an average temperature. 

E. Record the battery terminal float voltage. Use an accurate digital voltmeter. 

F. Take precautions to ensure that a battery failure will not jeopardize other equipment. Discharge the battery through a suitable resistor and an ammeter for 3 hours at rated 3-hour discharge current. Leave the charger in normal float operation and record each cell voltage every half- hour during discharge. Watch closely during the last hour and time the exact end point accurately. After ambient temperature correction to 77°F, if the minimum voltage of 1.75 in any cell is reached before 3 hours has elapsed, the test should be stopped and the ampere-hours discharge should be computed. Capacity can be determined by referring to figure 3. Testing should be done each year if the capacity is less than 90 percent of the original rating. The entire battery should be replaced as soon as possible after capacity drops below 80 percent of original. The battery cannot be relied upon in an emergency if it has deteriorated below 80-percent capacity. 

4. OPTIONAL INSTRUCTIONS LEAD-CALCIUM BATTERIES 

4.1 FLOAT CHARGE

For a typical, 60-cell, lead-calcium battery floated at 2.17 volts per cell and equalized at 2.33 volts per cell, the normal voltage range would be 130.2 to 139.8 volts. At many locations, the higher voltage cannot be tolerated for the 6 or more days required for equalizing, particularly where the battery is a source of power for electronic equipment. Lead-calcium batteries do not require equalizing if floated between 2.2 and 2.25 volts per cell. This voltage would give a 60-cell battery a voltage between 132 and 135 volts. Lead- calcium batteries have a distinct advantage when constant voltage is desirable. To match the battery voltage to the rated voltage of the equipment served, the number of cells should be selected to provide optimum voltage when floated to eliminate the equalizing charge. This procedure should be considered when replacing batteries. The table below lists some common voltage ranges. 

Table 2. - Common voltage ranges. 

Numb Voltage Range er (volts) of Cells 

12 26.4 to 27.0 23* 50.6 to 51.75 24 52.8 to 54.0 

58* 127.6 to 130.5 59* 129.8 to 132.75 

60 132.0 to 135.0 116* 225.2 to 261.0 120 264.0 to 270.0 

* The low battery alarm must be calibrated to reflect the lower number of cells.

4.2 INITIAL CHARGE

An initial charge is not required because the battery will charge properly at the above voltages. After about 2 weeks, initial cell voltages and specific gravity readings should be recorded on form POM-133A. Increase the voltage to 2.33 to 2.38 volts per cell (connected equipment permitting) if the initial charge must be completed sooner. 

4.3 VOLTAGE READINGS

A.. Each Shift((Attended Stations)  or During Routine Inspection (Unattended Stations)

Check the charger panel voltmeter to determine if the battery is being  

floated at the proper voltage. Adjust the battery charging voltage when necessary, and check when the power or station-service transformer taps are changed.  

B. Monthly

Check voltage across the battery terminals with an accurate digital voltmeter and adjust the panel voltmeter if necessary. Record pilot cell voltages to the nearest 0.01 volt, measured with an accurate digital voltmeter, on form POM-133A. Battery is functioning normally if all cells are above 2.14 volts. 

C. QQuuaarrtteerrllyy

Check voltages across all individual cells and record them on POM-133A. 

4.4 SPECIFIC GRAVITY READINGS

A. Monthly(Attended Stations)  or During Inspections  (Unattended Stations)

Read the specific gravity of the pilot cell. For accurate readings, hold the hydrometer vertically and use a long nozzle syringe about one-third down from the top. Record the pilot cell specific gravity, corrected for temperature, on form POM-133A. 

B. Quarterly

Read the specific gravity of 10 percent all cells and record, corrected for temperature, on form POM-133A. 

C. Annually 

Read the specific gravity of 100 percent of the cells, corrected for temperature, and record on form POM-133A. 

4.5 HEAVY DISCHARGE

The battery should be recharged as quickly as possible following a heavy discharge. This recharge can be done by raising the charging voltage to the maximum allowed by other circuit components but not greater than the range of 2.33 to 2.38 volts per cell. The battery should be returned to normal voltage after the capacity been restored. 

4.6 WATER REPLACEMENT

Add water only when the water level approaches the low level mark or prior to an equalizing charge. This step should be needed every 2 or 3 years with a proper charging program. 

Maintenance New Battery Shift Monthly 3-Month 6-Month Annual 

Visual General Inspection Inspection See 5.6 

Battery Float Panel Meter Battery Float Voltage Voltage Float with Digital Voltmeter See 5.7 Voltage 

Cell Float All Cells Pilot Cells All Cells Voltage with Digital with Digital with Digital See 5.7 Voltmeter Voltmeter Voltmeter 

Temperature All All Readings Cells Cells See 5.8 

Connection All 25 Percent All Resistance Connections of All Connections See 5.9 Connections 

Internal All All Resistance Cells Cells See 5.10 

Battery Acceptance Capacity Test 6 Testing Capacity months if 1-year See 5.11 Testing test <90 percent 

Safety Wash Equipment Equipment Protective Clothing See 5.6 & 8.0 Fire Extinguisher, etc. 

5. CONDENSED INSTRUCTIONS VALVE REGULATED LEAD-ACID BATTERIES (GEL CELLS) 

5.1 GENERAL

Valve regulated lead-acid batteries (VRLA) are usually manufactured in multi-cell blocks, (called modules) rather than single cells. The cases are often made of ABS plastic material and do not permit visual inspection of plates or electrolyte levels. They are called starved electrolyte or absorbed electrolyte cells and operate under a positive pressure. The hydrogen and oxygen are not expelled but recombined. Cells are sealed and require no water addition or specific gravity readings. These cells are typically lead calcium pasted-plate type cells with the electrolyte retained in gel or fiberglass mats. 

These batteries are normally used for emergency lighting, telecommunications, and other uninterrupted power supply (UPS) service. They are best applied where long slow discharges are needed. Heavy short discharges required for breaker operations are not recommended for this type battery. The life has been found to be only 18 months to 10 years in actual service. 

These cells are not flooded and do not effectively dissipate heat. This characteristic can lead to thermal runaway if ambient and battery temperatures are not carefully controlled (see 5.2 below). Cases have occurred in which the battery has burst into flame. Maintaining the cells as close as possible to 77 EF is imperative. Ambient temperature should be maintained as close as possible to 72 EF. Air circulation must be sufficient to eliminate any ambient temperature differences. The maximum cell temperature spread (hottest to coldest cell) should not exceed 5 EF, and the hottest cell should not be more than 5EF above ambient. Colder temperatures reduce capacity, and higher temperatures greatly reduce service life. About 50 percent of the service life will be lost for every 15 EF above 77EF. Do not allow sunlight or other heat sources to raise the temperature of individual cells. These cells are not recommended for station service because of these characteristics characteristics. 

VRLA modules/cells are typically shipped fully charged and do not require initial charge. 

5.2 FLOAT CHARGE

VRLA cells are typically floated at 2.25 to 2.30 volts depending on the manufacturer. Correct battery float voltage is critical for valve-regulated cells. The float voltage must be within the manufacturer’s recommended limits compensated for temperature. See the manufacturer’s literature for temperature compensation of float voltages. 

When VRLA cells are operated on float at normal full charge, no net chemical reaction occurs and almost all the overcharge energy results in heat generation. If the environment is such that the heat produced can be dissipated, no thermal runaway problem occurs. If the rate of heat generated exceeds the dissipated rate, the battery temperature rises and more current is required to maintain the float voltage. The additional current results in more heat generation, which raises the battery temperature further, and the cycle is repeated. Thermal runaway and destruction of the battery result. Elevated ambient temperature (above 72°F) or cell and/or charger malfunction will aggravate this condition. Ventilation and temperature control is critical for VRLA cells, and the battery should reach thermal equilibrium at no more than 5°F above ambient for the hottest cell. 

As cells approach full charge, battery voltage rises to approach the charger output voltage, and charging current decreases. The battery is fully charged when the charging current has not changed more than 10 percent for more than 3 hours. If the charging voltage has been set higher than float voltage to reduce the charging time, reduce the charging voltage to normal float value after the charging current has stabilized. Caution: Never exceed the maximum charging voltage recommended by the manufacturer. 

5.3 EQUALIZING CHARGE

Equalizing charge is not normally performed on VRLA cells. An equalizing charge may be necessary if a low float voltage is indicated or if a fast recharge is needed. The battery manufacturer should be consulted before proceeding if an equalizing charge is needed. The exact voltages and charge times indicated by the manufacturer must be followed carefully. 

5.4 CHARGER

A VRLA cell charger must have at least two capabilities: (1) extra electrical filtering to protect the cells from AC ripple, which may lead to thermal run­ away, and (2) temperature compensation to prevent thermal run-away. Do not try to charge these cells with a charger designed for a flooded lead-acid cells. 

5.5 BATTERY MAINTENANCE

The regimen described below is strongly recommended to maximize performance and life expectancy. See manufacturer’s data and IEEE 1188- 1996—Recommended Practice for Maintenance, Testing, and Replacement of Valve-Regulated Lead-Acid (VRLA) Batteries for Stationary Application for further information. 

5.6 VISUAL INSPECTIONS 

Visual inspections are made to assess the general condition of the battery, mounting rack and battery room, and safety equipment.  

A. Monthly

Check for general cleanliness of the battery, mounting rack, and battery room. Check for electrolyte leaks and cover integrity, and take corrective action if needed. Check for corrosion at terminals, connectors, racks, and cabinets. Check the ambient temperature and make sure all ventilation equipment (fans, vents, etc.) is operable. 

Check for availability and condition of all safety equipment, gloves, aprons, face shields, etc. Check for a full gallon of labeled neutralizing solution. Check for cleanliness and operability of eyewash station or portable eyewash equipment and body wash station (see section 8.2). Check for a class C fire extinguisher and ensure that it has been inspected and tested according to schedule. Carbon dioxide (CO2) fire extinguishers are not recommended because of the cooling effect they will have on the battery. Check for availability of insulated tools and utensils so short circuits can be avoided. 

5.7 VOLTAGE READINGS

An accurate digital voltmeter is critical for extended life of the battery (see section 1.3). At a constant float voltage, the charging current will increase as the temperature of the electrolyte increases. Therefore, cells of higher temperature will indicate a lower cell voltage. See figure 10 for proper meter probe placement. Place the probes across the posts of the cell so as not to include the voltage drops across the inter-cell connections. 

A. Initial Voltage 

Readings of all cells should be taken and recorded about 24 hours after placing the battery in float. Select the cell/module with the lowest float voltage as the pilot cell for future readings. Use form POM-133B for all voltage readings. 

B. Each Shift

Check the voltmeter on the charger and adjust the float voltage if necessary. 

C. When Taps Are Changed

When taps are changed on the power or station service transformers, check the float voltage on the charger panel and adjust if necessary. 

D. Monthly

Check and record the voltage of the pilot cell with an accurate digital voltmeter. 

E. Monthly

Check and record the float voltage across the whole battery with an accurate digital voltmeter. Compare this reading to the panel voltmeter and adjust the panel meter to agree with the digital meter if necessary. 

F. Every Six Months

Check and record the voltage of each individual cell with an accurate digital voltmeter. 

5.8 TEMPERATURE READINGS

A. After Installation

After 24 hours on float and the temperatures have stabilized, record temperatures of each individual cell on form POM-133B. Use an accurate surface thermometer and take the readings on the negative posts. Accurate readings are critical for extended life and performance. Check the thermometer for accuracy at least once per year. Take all temperature readings only on float. Do not try to take post temperatures while the battery is discharging. The resistance of the connections causes errors in temperature readings. An accurate IR camera may also be used for temperature readings. 

B. Quarterly

Take temperature readings of each individual cell and record them on form POM-133B. Compare readings with the initial and all prior temperatures for trending purposes. The highest temperature cell will typically also have the lowest voltage. 

5.9 CONNECTION RESISTANCE

See section 1.6C for detailed instructions. 

A. After Installation

Record resistance of each connection between the cell post and the interconnection strap on form POM-134B. Contact the manufacturer for expected readings for specific cells. See figure 2 in section 1.6C or figure 10 at the back of this FIST for resistance probe placement. Clean, re-torque, and re-coat with no-oxide grease any connection with a resistance 20 percent or more above the manufacturer’s recommended value. Use these values as a baseline. Caution: Never put meter leads across a cell with the function switch on ohms. This procedure will place a voltage across the meter instead of a resistance. 

B. Quarterly

Record the resistance of 25 percent of the connections as in step A above 

Rev.12/31/97 35 

and compare them with the previous readings. Rotate the measured connections each quarter. Repair those that have increased 20 percent in resistance. 

C. Annually

Record the resistance of all the connections as in step A above and compare them with the previous readings. Repair those that have increased 20 percent in resistance. 

D. During Discharge

Connection integrity may be checked with an accurate IR camera. Temperature of the higher resistance connections will be noticeably higher and should be repaired. 

5.1   INTERNAL RESISTANCE

Internal resistance is a good indication of the state of charge and substitutes for specific gravity readings taken on flooded, lead-acid type cells. Measuring the internal resistance of a module monitors the two main failure modes—grid corrosion and dryout. The manufacturer’s literature will list the normal expected values. This test should not be done until after the connection resistances of the cells are checked and repaired as in 5.9 above. Elevated connection resistance will appear as internal resistance and make cells appear faulty. Internal resistance can be checked as follows: 

1. While the battery is fully charged and operating on float, check and record voltage and current for the cell being tested. 2. Apply a normal load across the cell. 3. Again check and record the voltage and current. 4. The internal resistance can then be calculated by dividing the change in voltage by the change in current. 

Commercial test sets are available to measure internal resistance, which saves time and effort. Consider purchasing a test set if maintaining more than one VRLA battery. 

A. Upon Installation

After the battery has reached equilibrium (1 to 3 days) on float, perform the internal resistance check on each cell/module and record the results on form POM-134B as a baseline for future comparisons. 

B. Quarterly

Perform the internal resistance check on each cell and compare the results with the initial records. Changes in the internal resistance of 20 percent or greater should be considered significant. Contact the battery manufacturer and follow their recommendations. 

5.11 TESTING

A. Upon Installation

Acceptance capacity testing should be performed within 1 week after the battery has reached equilibrium in charge and temperature. Operating temperature of the battery will greatly affect the available capacity, and manufacturer’s data must be consulted for correction factors. Maintain accurate records of tests, including all equipment used and test results. These records can be used as baseline for later comparisons. 

1. Conduct the test only after a connection resistance test has been performed as in 5.9 above. 

2. Install an accurate ammeter, voltmeter, and temperature instrumentation, and provide an accurate stopwatch or other means to indicate elapsed time. Minimum test time should be at least 1 hour. More time is recommended for critical applications and test accuracy. 

3. Provide a variable load resistance so that constant current can be maintained equal to the rating of the battery for the selected test time. 

4. Disconnect the charger. 

5. Read and record individual cell/module voltages and the battery terminal voltage. The readings should be taken after applying the load at the beginning of the test. Repeat the readings at specified intervals and plan the test time long enough in advance to provide a minimum of five sets of readings. Caution: Take individual cell voltage readings between respective terminals of like polarity ( positive to positive) so the voltage drop of the intercell connectors will be included. See figure 10 for probe placement. 

6. If an individual cell/module is approaching reversal of its polarity (zero volts) or a module voltage is 2 volts or more lower than the others, but the overall terminal voltage has not reached its test limit, bypass the cell/module and continue the test. Perform the bypass connection away from the cell/module to avoid arcing. A new minimum voltage based on the remaining cells should be established for the remainder of the test (1.75 times the number of remaining cells).

Consult the manufacturer and prepare to bypass cells in advance. The possibility of weak cells is high, especially as the battery ages. 

7. Maintain the discharge rate until the battery terminal voltage decreases to a value equal to the manufacturer’s specified minimum voltage per cell (usually 1.75 volts) times the number of cells. 

8. Battery capacity can then be calculated by dividing the actual time to reach specified terminal voltage by the rated time to specified terminal voltage and multiplying by 100. 

Percent Capacity =  actual time x 100 rated time 

B . Annually

Perform a discharge capacity test with the same set-up and equipment as in step A above. 

C. Every Six Months

Perform a discharge capacity test as in step A above, after the battery falls below 90 percent of its original design capacity on the annual test. Replace the battery as soon as possible after it falls below 80 percent of its original design capacity rating. 

D. Continuity Tests 

Continuity tests are performed on a non-routine basis, whenever the integrity of the battery is suspect. A VRLA cell typically fails open, and continuity through the cell is lost. This condition is not readily apparent. A quick check is to turn off both chargers and see if the battery will accept the load of the connected equipment. Another method is to place a test load across the battery and see if it will accept load. If cells/modules are connected in parallel, the load must be placed across individual cells/modules to detect an open circuit. Contact the manufacturer if further information is needed.