11.BATTERY TROUBLES SUMMARIZED

A. A. Lack of Gassing 

Lack of gassing while on charge may indicate an internal short between plates, i.e., the cell discharges internally as fast as it is being charged. 

B.. Specific gravity or voltage

Specific gravity or voltage of a cell lower than other cells is an indication of excessive internal losses and may result from consistent undercharging. 

C.. COOLER

Color or appearance of plates or sediment different from other cells is addressed below: 

1. Patches of white lead sulfate on either the positive or negative plates: caused by standing idle or undercharging for extended periods. 

2. Antimony deposit dark-slate patches on negative plates (usually near the terminal): caused by charging at too high a rate or an aged cell nearing the end of its service life. 

3. Top layer of sediment white: caused by undercharging. 

4. Lumpy brown sediment: caused by overcharging. 

5. All white sediment no visible layers: caused by overcharging after prolonged low float voltage. 

6. Large flaking on the inter plate collector bar: caused by being on float charge for extended periods at insufficient float voltage without equalizing charging being performed. 

D. Plate Problems

If any checks below are excessive, capacity tests must be run to determine if individual cells or the entire battery should be replaced. See section 3. 

1. Cracks on the edges of the positive plate grids. 

2. Light-colored sulfating spots on edges of plates below cracks mentioned in check No. 1 above. 

3. Excessive sediment in the bottom of the case. 

4. “Mossing” or “treeing” on the tops of negative plates. 

E.. WATER

1. Cell uses excessive water (check fig. 1 for typical water consumption): caused by excess charging rates, high operating temperatures, or leaking cell. 

2. Cell requires very little water: caused by insufficient charging. 

FF. Buckling of PlatesBuckling of Plates

Buckling of positive plates indicates excessive sulfation caused by undercharging or excessive temperature. See sections 2.10, 2.22, and 2.23. 

GG. FFaaiilluurree  ttoo  SSuuppppllyy  RRaatteedd  AAmmppeerree--HHoouurr  LLooaaddss

Failure to supply rated ampere hours indicates discharged condition, excessive sulfation, or loss of active material from positive plates. Cells may be worn out or active material may be gone from positive plates. See section 3 for testing. 

H. Surface Charge Phenomenon

When a battery has been on float charge for a long time and is put under load with the chargers off, the voltage will drop rapidly. This drop is caused by plugging of some of the pores on the surface of the plates, which partially blocks the transfer of ions. The voltage may drop below the low-voltage alarm and trip settings. After this initial drop, the voltage will usually increase to a level above the low-voltage alarm and trip settings. The battery will then operate normally until its capacity is exhausted. 

If the battery is exercised (partially discharged) on a routine basis, the voltage dip can be reduced or eliminated. Turning off both chargers and allowing the battery to take the load for at least 15 minutes exercises the battery. The first few times this procedure is performed, disconnect the low voltage trip relay to prevent an inadvertent trip. The first time the battery is exercised, the procedure should be performed several times in succession until the voltage drop stays above the alarm setting. Always give the chargers time to reduce charging current to float value before turning off the chargers again for the next cycle. 

Each battery has its own characteristics, and the frequency of exercising should be adjusted so that the voltage drop does not cause the low voltage alarm. Start at a monthly cycle and experiment with increasing the time between exercises. The proper time between exercises exists when the voltage drop is just above the alarm relay setting. 

1..2 RECOMMENDED ACTIONS

If any cells seem to be in trouble, the whole battery should be given an 

Rev.12/31/97 13 

equalizing charge, and then specific gravity readings should be taken on all cells. If all cells gas evenly and specific gravity of every cell is normal, all the battery needed was the charge. Otherwise, all low gravities should be recorded, and an extra thorough charge, as described in section 1.2C should be given. The temperature of all cells should be compared by thermometer or IR camera with the rest of the cells. Sulfated cells will run hot enough to cause damage if not corrected. Any cells that still will not gas with the extra charging should be investigated for impurities and inspected for internal short circuits. See section 3 for testing. 

Additional information may be obtained from IEEE Standard 450- 1995—Maintenance, Testing, and Replacement of Vented Lead-Acid Batteries. If this standard does not help solve a problem, record the voltage of each cell and the specific gravity of 10 percent of all the cells. Also, record the electrolyte temperature and the ambient temperature, then contact the battery manufacturer for assistance. 

1.3  CELL PRE0PLACEMENT

A faulty cell may be replaced by one in good condition of the same make, type, rating, and approximate age. A new cell should not be installed in series with older cells except as a last resort. A battery may be operated without several cells by proper adjustment of float and equalizing voltages, provided discharge capacity requirements can be met. 

2. LEAD-ACID BATTERY PRINCIPLES 

2.1 PURPOSE

This section describes the principles of lead-acid battery care and how to determine if the care is adequate and correct. The most important part of battery care is a proper charging program. Keeping and comparing accurate records of physical conditions and measured data assists in determining whether the charging program is correct. Correct charging is critical for long battery life and reliability of service. 

The following discussion describes cell conditions with both proper and improper operation and maintenance. These principles do not take precedence over the manufacturer's instructions, but provide explanations and details. 

2.2 FULL CHARGE

Knowing when a cell is fully charged is important. A cell is fully charged when, charging at the equalizing rate, the cell is gassing, specific gravity has stopped rising, and specific gravity remains constant for two successive readings. Hydrometer readings must be corrected for any changes in cell temperature that have occurred between readings. These two readings should be taken during the last one-eighth of the charging period. 

2.3 APPEARANCE OF NORMAL CELLS

Edges of positive plates do not give much information. Edges of negative plates should be uniformly gray; they should be examined with a non­ metallic flashlight for sparkling from lead sulfate crystals. Correct float charging will cause no lead sulfate crystals. See section 1.10 for more information on cell appearance. 

No visible change occurs when the cell is discharged a normal amount. If the charging program is correct, sediment accumulates very slowly and should never be white or lumpy. The charging program may require changes to produce a very scanty, fine, dark-brown sediment. The electrolyte should be at the marked level, midway between top of the case and top of the plates. 

2.4 CHEMICAL CHANGES

A fully charged cell has brown lead peroxide on positive plates and gray sponge lead on negative plates. 

On discharge, electric current converts active materials of positive and negative plates to normal lead sulfate and uses up sulfuric acid to manufacture lead sulfate. This process leaves the acid weak at the end of the discharge. Lead sulfate is white in color but cannot be seen on plates unless the cell is over-discharged, which produces over sulfation. This condition makes the plates first lighter in color and finally mottled white in patches or white all over. 

Charging the cell reverses this process, converting lead sulfate in the plates to lead peroxide and sponge lead and producing sulfuric acid, which restores the specific gravity to normal. Chemical reactions in a storage cell are: 

Battery Discharged Battery Charged 

(+ plate) (- plate) (solutio (+ plate) (- plate) (solution) n PbSO4 PbSO4 2H2O PbO2 + Pb 2H2 SO4 + + + 

(lead sulfate) (lead sulfate) (water) (lead peroxide) (lead) (sulfuric acid) 

As the charge nears completion little lead sulfate remains to convert to lead. The charging current begins to separate water into oxygen and hydrogen, which bubbles to the top of the electrolyte and forms a mixture of very explosive gases. 

Quantity of ampere-hours available from a cell decreases with an increasing rate of discharge. Available ampere-hours are much less at rapid rates of discharge (see fig. 3). The ampere hours also decrease for cells with weaker specific gravity (see fig. 4). 

2.5 INTERNAL SELF-DISCHARGE AND EFFECT OF  IMPURITIES ON FLOATING VOLTAGE 

Lead-calcium and lead-selenium cells have the advantage of low internal losses, which remain constant for the life of the cell. Lead-selenium cells 

Rev.12/31/97 16 

contain little antimony and do not have antimony migration like lead- antimony cells. 

Fully charged lead-antimony cells discharge internally by an action between active material and the grid. Impurities may hasten this action and may result in visible or invisible changes on the plates depending on the types of impurities present. No metals should be put into the electrolyte at any time, except a cadmium test electrode. Impurities may prevent a proper floating voltage from keeping up the charge and may prevent an equalizing charge from equalizing voltage, so a higher floating voltage may be required. 

The rate of self-discharge is decreased by using a lower specific gravity. The rate increases as the cell temperature rises, as may be seen on the curves of figures 5 and 6. The charge will not be lost if a small charging current, just equal to the self-discharge rate, is given to the cell. This charge is known as a trickle charge and is usually made a little larger than necessary so as to gradually restore losses caused by small loads connected to the battery. 

Self-discharge increases with age to perhaps five times the initial rate. This process is believed to be caused by the antimony being deposited on the negative plate in a form that behaves as an impurity. Many batteries use calcium instead of antimony as the alloying material, which reduces the internal discharge as indicated on figure 7. 

2.6 TEMPERATURE CHARACTERISTICS

Operating temperature greatly affects performance of storage cells. Capacity is greatly reduced when cold, as shown by figure 8. The self-discharge rate is increased at warm temperatures, as shown by figure 7. The temperature at which the electrolyte will freeze and burst cells is lowered as specific gravity rises. Little danger of freezing exists if the battery is kept well charged. 

If charging current is kept constant, charging voltage will rise to a final value and is one indication that full charge has been reached. This final voltage increases greatly as the cell gets colder, as shown by figure 5. For this reason, do not try to terminate an equalizing charge by a relay that operates at a constant voltage. This procedure would only work correctly for one temperature. Relays are available where operating voltage varies with temperature. This charge control must be subject to the same ambient temperature as the battery. 

If charging voltage is held constant, final charging current increases with temperature, as also shown in figure 5. This condition is needed to offset the increasing internal self-discharge current. The constant voltage charge method automatically keeps the current at the value the battery needs for replacing both the self discharge and load discharges. 

2.7 PROPER AMOUNT OF CHARGE

If cells of either lead-antimony or lead-calcium are undercharged, service will be poor and battery life short. If overcharged , service with either cell type will be good, but excessive overcharging will shorten life. Proper charging, means slight overcharging to cause the least possible sedimentation and a minimum of heavy gassing. This condition requires very little makeup water. No perceptible sedimentation or buckling of plates occurs during charge at high or low rates if cells are not allowed to gas vigorously. Sedimentation starts with gassing and is proportional to the total amount of gas liberated. Lead- selenium cells do not have the grid growth or the lead-antimony cell problems. Typical curves of recharge times after 100-percent discharge at the 8-hour rate are shown in figure 9. 

2.8 HIGH RATE OVERCHARGING

After a battery is fully charged, continuation of charging current at a high rate damages positive plates. Violent gassing takes place, bubbles form in the interior of the active material, and the resulting pressure forces bubbles through the porous active material. The active material restrains the bubbles sufficiently so that many particles of plate material are broken out. These particles rise with the bubbles and result in a muddy red or brown color of the electrolyte. Some of this fine sediment settles on negative plates where it short circuits. The sediment is converted to gray sponge lead and results in a growth of moss-like sediment deposited on top edges of the negative plates. This deposit indicates that high-rate overcharging previously occurred. The battery will overheat on sustained heavy charge rates. The temperature of the cells should never intentionally be allowed to exceed 100 °F. 

2.9 LOW RATE OVERCHARGING

At lower rates of overcharge, bubbling is reduced and sediment falls to the bottom of the cell. Overcharging at a very slow rate disturbs electrolyte so little that fine brown sediment falls in a vertical line, forming tiny ridges on top of the sediment. Ridged sediment is a good indication that the recent overcharging was not at high rates. Obviously, overcharging should be kept at a minimum, and ridges should be small. 

2.10 UNDERCHARGING

If the battery gets too little charging, unconverted sulfate remains on the plates too long and hardens. The longer plates stay in less-than-full-charge condition, the harder the sulfate becomes and the more difficult it is to reconvert. When new, the sulfate is easily converted back to soft active materials by a normal charge, but a long overcharge is required to remove it after becoming hard. Sulfate accumulates unnoticed, a little on each charge, if charging is not enough to eliminate all the sulfate. This residue build-up continues until a substantial portion of ampere-hour capacity is lost. The remedy is to increase charging to give a slight overcharge. This procedure must be put into practice while the battery is new and followed for the life of the battery (see also paragraph 1.2C—Equalizing Charge). Prolonged undercharging also leads to large flaking on the interplate collector bar. 

Sulfate build-up caused by undercharging is the most common cause of buckling plates and cracked grids. Sulfate takes up more room than the original material and strains the plates out of shape. The pressure of expanding active material can break separators and cause short circuits. 

A badly sulfated cell should be treated as described in section 2.24. If charged at too low a rate, the hardened sulfate is thrown out of plates and settles in white ridges on the cell bottom. At higher rates, the gassing distributes the sediment evenly without ridges. An over sulfated cell has high internal resistance and requires extra voltage across the cell, which also causes them to develop higher temperatures on charge. Buckled or cracked plates cannot be repaired by removal of sulfate but may be used as long as they retain satisfactory ampere-hour capacity. See section 3 for capacity testing. 

2.11 OVER DISCHARGING

The plates suffer greatly when over discharged. Voltage per cell should not be allowed to drop below 1.75 volts. Specific gravity should not be allowed to decrease below the limit given by the manufacturer, which is different for various types and sizes of cells. As normal discharge proceeds, active materials are converted to normal lead sulfate, which requires only slightly more space than active materials. Over discharge forms more lead sulfate in the pores of the active material than they are able to hold. This process may expand and bend or buckle plates or crack grids. In some instances, sufficient pressure is created to crack or puncture separators. 

2.12 SEDIMENTATION

The history of each cell is shown by the sedimentation because successive layers are laid down in colored strata.. These layers can be seen edgewise against the inside of the case. Layers of fine, dark gray show periods of excessive charging (current too high or charge too long). Lumpy gray layers indicate times the battery was over discharged. These layers are generally covered by a layer of white sulfate from the following charge. A considerable amount of sediment and slivers will be found initially in Gould processed plate batteries. This condition is a normal result of the forming process. Some additional sediment and slivers will be dislodged in shipment and will accumulate at the bottom of the case of these batteries during the first few equalizing charges. With this exception, a perfectly charged battery should have nothing but fine brown sediment, free from lumps and as scanty as possible. If some experimenting is done with the charging program, slight undercharging may result in a white sulfate layer. This layer indicates that the charging should be slightly increased. 

Rev.12/31/97 19 

2.13 REPLACEMENT WATER

As batteries are charged, a small quantity of water in the electrolyte is broken down into hydrogen and oxygen by the charging current. The gases are dissipated through openings in vent plugs. As this process takes place, electrolyte level gradually lowers until distilled water must be added. Commercially available "demineralized" water has been found by test to be equal or superior to commercial or "in plant" distilled water. References throughout this bulletin to "distilled water" do not preclude the use of "demineralized water.” Do not add water in excess of the maximum level mark. Never store distilled water in a metallic container. Use glass, plastic, or rubber containers. 

Water consumption of batteries is indicated on figure 1. Take an average of the amount of water added over several months and compare with the amounts given on figure 1. 

2.14 WATER REPLACEMENT RATE FOR LEAD-ANTIMONY CELLS

Lead-antimony cells begin their lives with low water consumption, which increases as much as five times toward the end of their lives (see fig. 1). Capped cells evaporate very little water, and loss is caused by gassing and is proportional to the amount of charge the battery receives. Heavy gassing requires frequent additions of distilled water. The water should be added just before or at the beginning of a charge so that gassing will ensure thorough mixing before specific gravity readings are taken. Proper charging minimizes distilled water replacement by limiting the amount of gas generated to a small quantity. This method is much easier than overcharging and having to refill cells frequently. It also extends the life of the battery. 

2.15 WATER REPLACEMENT RATE FOR LEAD -CALCIUM CELLS

Frequent additions of distilled water in small amounts are not desirable. Water additions two or three times a year will probably be sufficient at most installations. The electrolyte in all cells should be maintained within 1/4 inch below the high level mark. Calcium cells, because of greater purity of their components, require only about one tenth the water needed by equivalent size antimony cells. This low requirement remains constant during the entire battery life. See figure 1 for water consumption rate. 

22.16  WATER REPLACEMENT FOR LEAD SELENIUM CELLS

Water replacement should only be necessary every 12 to 18 months if the battery is not subjected to many discharges. If several discharges are experienced, water replacement should be performed as with the lead- calcium cells in paragraph 2.15 above. Water consumption is low throughout the life of these cells. 

22.17 ADJUSTING SPECIFIC GRAVITY

Specific gravity should nneevveerr be adjusted until the gravity is definitely established to be wrong. Before adjusting for low gravity, make sure that the gravity cannot be raised by equalizing (see 1.2 C). Continue the charge until the specific gravity shows no rise, and then charge for 3 more hours. Hydrometer readings must be taken as indicated in 2.18 below. Never make a gravity adjustment on a cell that does not gas on charge. Remove some electrolyte from the cell and replace it with pure, 1.300-gravity sulfuric acid, which consists of 30-percent concentrated acid and 70-percent distilled water by volume. Recharge until all cells gas for an hour. Repeat the procedure if the gravity is still not normal. To lower the gravity, replace some of the electrolyte with distilled water. 

22.18 HYDROMETER READINGS

Provide two hydrometers of high accuracy and sensitivity and check them against each other frequently. The hydrometers should be replaced every 2 to 3 years. The hydrometer must be held vertically for accurate specific gravity readings. Do not take readings after adding water (or acid) until the electrolyte has had time to mix thoroughly (not less than 1 hour when gassing or 2 days if not gassing for antimony cells, and several weeks for calcium cells in floating service). Use a long nozzle syringe and take samples several inches down to minimize errors. Bubbles in the electrolyte cause errors, and readings should not be taken sooner than 15 minutes after gassing has stopped. 

Specific gravity of electrolyte must be corrected for temperature. Subtract one point (0.001) from the specific gravity reading for each 3 EF the temperature is below 77 °F, and add one point (0.001) for each 3 EF the temperature is above 77 °F. The recommended specific gravity spread between all cells is 0.010. 

22.19 CONSTANT VOLTAGE CHARGING

Constant voltage charging is the preferred method because of extended service life. If charging equipment is suitable for a continuously floating charge at a constant voltage, the proper floating voltage should be chosen from the manufacturer’s data. If the voltage is given for a single cell, multiply this voltage by the number of cells in the battery. 

22.20 BATTERY LIFE FOR DIFFERENT TYPES AND SERVICES

The life of various types of cells can vary markedly. Valve regulated lead- acid cells have the shortest life. Formed plates of the Plante or Manchex type on light duty and floating charge have a longer life, usually 14 to 18 years. Pasted plate Plante cells may be expected to last in excess of 25 years on float charge. Formed plate cells, if cycle charged, usually last only about 9 years. Lead-calcium cells on constant float charge typically last 12 to 15 

years. Lead-selenium cells have a longer life expectation than lead-calcium or lead-antimony. A battery is considered worn out when it fails to deliver 80 percent of its original capacity. 

22.21 CLEANLINESS

Battery connections must be clean, bright, and free of corrosion for the battery to perform. Corrosion that is not cleaned off terminals periodically will spread into areas between posts and connectors. This condition will develop into a high resistance connection and cause heating and wasted capacity. The battery and surrounding parts should be kept clean, dry, and free of acid. Sulfuric acid absorbs moisture, and spilled electrolyte will not dry up. If electrolyte is spilled or sprayed out of the cells on charge, neutralize with a solution of baking soda (1 pound of soda to 1 gallon of water), then rinse with distilled water and dry with a soft cloth. A labeled jar of soda solution at least one gallon, must be kept in the battery room. Care should be taken to prevent the solution from getting into the cells. Make sure vent plugs are open, flame arresters and dust caps are in place, and all components are in good condition. 

22.22 INTERNAL SHORTS

A short circuit through a separator may be caused by: 

1. Insufficient charging causes material in the plates to become mostly lead sulfate. The lead sulfate expands and, if the grid does not crack to relieve the strain, the plate will become distorted. This condition is commonly known as buckling. The buckling is most pronounced at the four corners of the positive plates, where shorts are most likely to occur. 

2. Impurities in the solution caused by using contaminated water or dirty utensils. 

3. Excessive overcharging causes the grid specific gravity to be partially converted to lead peroxide, which reduces mechanical strength and allows positive and negative plate contact. 

A short in a cell can be detected by falling specific gravity and falling cell voltage. In some cases, an orange discoloration occurs at the point of the short. If a short is long standing, disintegration of the positive plate will occur at the point of contact with the negative because of the conversion of positive plate material to negative. 

22.23 NORMAL SULFATE AND OVER SULFATION 

During discharge of a battery, "normal" sulfate is formed, which is required to produce current. If charging is neglected, the sulfate fills the pores of the plates and makes the active material dense and hard. This condition is referred to as "over sulfated." 

Normal lead sulfate formed on discharge is in a form that a charge will easily reconvert. When a battery is "over sulfated," plates are less porous than normal and absorb a charge with difficulty. With this condition, an ordinary charge will not reconvert all the sulfate to sulfuric acid and specific gravity remains below normal. Active material of "over sulfated" negative plates is light in color and either hard and dense or granular and gritty and easily disintegrated. The negative plates require the prolonged charge necessary to restore an "over sulfated" battery. An individual cell may become "over sulfated" by external grounding, by an internal short, or by drying out because of failure to add water. Over sulfation may also be caused by prolonged low float charging. 

22.24 ELIMINATION OF OVER SULFATION 

A battery or cell that is "over sulfated" should be charged fully in the regular way until specific gravity stops rising. Then one of the weakest cells should be discharged through a load resistor at the normal 8-hour discharge rate to a final voltage of 1.75 volts. The battery is not over sulfated if the representative cell gives normal capacity, that is, about 100 percent rated capacity for a fairly new battery or down to 80 percent of initial rated capacity for a battery nearing the end of its expected life. 

If the above capacity is not obtained, possible over sulfation should be treated as follows: 

1. In cases where one or more individual cells have become "over sulfated" and the rest of the battery is in good condition, these cells should be treated separately after removing them from the circuit. 

2. Recharge the removed cells at half the 8-hour discharge rate. Record hydrometer readings and temperature at regular intervals (3 to 5 hours) during the charge to determine if rising specific gravity has peaked. Maintain constant electrolyte level by adding water after each reading. Do not add water before taking readings. 

3. Continue the charge, recording the readings until no further specific gravity rise has occurred in any cell for 10 hours. If the temperature reaches 100 °F, reduce the current or temporarily interrupt the charge so as not to exceed this temperature. When the specific gravity has reached maximum, terminate the charge and record the hydrometer reading of each cell. 

4. The cells must be replaced if they again fail the capacity check in 2.24. 

22.25 WATER TREATMENT FOR OVER SULFATION

In cases of emergency such as plant power loss or loss of both chargers, a long discharge to the point of over-discharge may make the battery difficult to recover. Over sulfation may have occurred such that prolonged charging set forth in section 2.24 may not recover the battery. 

The water treatment should only be attempted in an emergency as a last last resort after prolonged charges will not restore the specific gravity. 

The principle is to reduce the specific gravity in steps by removing a portion of the electrolyte and replacing it with distilled water, then charging the battery after each step. As the specific gravity is reduced and the charge is applied, the sulfate is dissolved from the plates by lower specific gravity electrolyte at each step. The electrolyte becomes more and more like pure water, making it easier for the sulfate to transfer off the plates into the electrolyte. Once the sulphates have been dissolved and removed, the process is reversed to bring the electrolyte back to normal specific gravity. 

The steps are as follows: 

1. Reduce the specific gravity to about 1.050 to 1.100 by removing some of the electrolyte and replacing it with distilled water. 

2. Charge the battery at the equalizing rate until the specific gravity of the pilot cell stops rising for two consecutive readings. However, do not charge longer than 48 hours before the next step. 

3. Again reduce the specific gravity as in step 1 above and repeat the charge in step 2. 

4. Repeat the above steps until the maximum specific gravity obtained at the end of a charge is less than 1.150. 

5. Reverse the above process by removing some of the weakened electrolyte and replacing it with 1.300 specific gravity acid. The amount to be replaced is about the same as that in step 1 above. Do not try to speed up the process by replacing more of electrolyte than that removed in steps 1 through 4. 

6. Charge the battery as in step 2 above, checking the specific gravity of 10 percent of the cells. 

7. Repeat steps 5 and 6, increasing the specific gravity until it is just below normal operating value. Record the specific gravity of all the cells on the last step. 

8. Place the battery back under normal float charge and service. 

Rev.12/31/97 24 

9. After 1 month under normal service, the battery should be given a capacity test to see if the battery must be replaced (see section 3.2).