Battery 101
CELL ARRANGEMENT:
Motive power lead-acid batteries for electric powered industrial trucks, tractors and cranes typically consist of 6, 12, 18 or 24 cells, a steel tray into which the cells are assembled, a battery terminal connector and other components necessary to secure and protect the cells and provide the necessary electrical interconnections.
Battery Identification
The essential information, necessary for proper care of an industrial motive power battery, appears on the battery either stamped into one of the intercell connectors or on a name plate affixed to the tray. This information usually includes the model, number of plates per cell, battery capacity, battery voltage, serial number. Some manufacturers list, as a part of the model or type designation, the rated ampere-hour capacity of a single positive plate, such as “X75” As an alternate means of determining rated battery capacity this number should be multiplied by the total number of positive plates in one cell. To find the number of positive plates in a cell, subtract one from the total number of plates and divide by two. To find the capacity of a battery designated “X75-19” therefore: 19-1=18; 18/2=9; 9 x 75=675 A.H. battery capacity.
Cell Arrangement
The individual cells, which contain the energy generating components of the battery, may be arranged slightly differently for various types of batteries. The typical cell arrangement for 12 volt batteries (6 cells) is a single row of 6 cells; for 24 volts (12 cells) it is either two rows of 6 cells each or three rows of 4 cells each; for 32 volts (16 cells) it is four rows of 4 cells each; and for 36 volts (18 cells) it is three rows of 6 cells each. The cells of all motive power batteries are, however, always connected in series to produce the required voltage. Cell and battery capacity, which is the available ampere-hours or watt-hours, is a function of the total number and size of plates within each cell. Voltage, though, is the same for all cells regardless of size. Each lead-acid cell yields a nominal 2 volts.
Connector Arrangement
Connections between cells are made by intercell-connectors which may be lead coated copper straps or cast of solid lead. These connections are always welded, in proper sequence, by the application of heat to the terminals of the cells. Total energy from the battery is drawn off by terminal cables which extend beyond the steel tray wall and are in turn permanently joined to the battery terminal connector.
CELL :
This is the basic unit of any battery. It is a galvanic cell which produces electrical energy when connected to an electrical load and, after being discharged, may be restored to its original fully charged condition. It has a nominal voltage of 2 volts and consists of an element, from which the energy is derived, and electrolyte, both of which are contained by an impact resistant, molded rubber or plastic jar. The element is prevented from contacting the bottom of the jar by means of a high impact bridge which consists of a series of support ribs. These ribs provide sediment space below the bottom of the element to accommodate particles of active material, shed by the positive plates during normal operation of the battery. The top of each cell is fitted with a molded rubber or plastic cover sealed to the jar at the edges. A vent or filler cap is located in the center of the cover. This permits the escape of hydrogen and oxygen while the cells are gassing and, when removed, provides an opening through which water may be added to the cell. The positive and negative terminal posts, which are part of the element, fit through openings in the cover. Cells prior to being connected together are so placed that the positive terminal of one cell is adjacent to the negative terminal of the next. This permits a series connection. On some batteries the cell covers are tightened to the terminal posts by seal nuts and gaskets. On others, lead bushings are molded into the covers and welded to the terminal posts. Both methods prevent leakage of acid from the area around the terminal post.
Element
The element of the cell consists of one group each of positive and negative plates meshed together. The plates are insulated from each other by separators which are inserted between all plates. A plastic element protector is positioned on top of the separators which prevents mechanical damage to the element and aids in preventing electrical shorts which occur when particles of active material bridge the space between plates. Terminal posts are welded to each group and are used to electrically connect one cell to another.
Group
This is an assembly of plates of like polarity connected in parallel by welding to a common strap or busbar. A cell must contain one positive and one negative group. The negative group always has one more plate than the positive group. One or more terminal posts are welded to each.
Plates
The electrodes or plates are either positive or negative and consist of a cast lead alloy grid and active material. The grid provides support to the active material and becomes the primary electrical conductor. The active materials result from the addition of chemicals to lead oxides which are converted, by electro-chemical process- ing, to lead dioxide in the positive and sponge lead in the negative. Although negative plates made by all industrial lead-acid battery manufacturers are pasted and essentially similar, the positive plates in common use may be either tubular or pasted type.
Tubular type
The grid of the tubular plate consists of a series of cast lead rods connected at the top These vertical rods become the conducting cores of a like number of porous, tubular, glass or plastic retainers which contain the active material. Each tube is sealed at the top and bottom after filling to prevent the loss of active material.
Pasted type
The grid of the pasted plate consists of horizontal and vertical or diagonal cast lead conducting members within a rectangular cast frame. A slurry of active material is pasted or squeezed into the voids and the surfaces are then covered by porous glass and plastic retainers to prevent the loss of active material.
Electrolyte
The element within the jar is immersed in an electrolyte, which is a solution of sulfuric acid and “pure" water. This permits the necessary chemical reaction to occur and provides a conducting medium in which the flow of electric current takes place. The electrolyte in a fully charged cell normally has a specific gravity of between 1.275 and 1.395 at 77 degrees F. As a cell discharges, the specific gravity decreases. Measurement of this specific gravity. by means of a hydrometer, indicates the state of charge of a cell. To save time, in determining this state of charge for the battery, a pilot cell or cells may be chosen. This is a selected cell(s) whose condition is assumed to be representative of the condition of the entire battery.
Separator
Separators are made from either micro-porous rubber or plastic, both of which are resistant to heat and acid. Separators provide mechanical and electrical insulation between positive and negative plates but are porous enough to permit passage of electrolyte. The grooved or ribbed side of the separator is placed toward the positive plate to allow a free flow of electrolyte to the active material. The flat side faces the negative plate to contain the sponge lead.
Positive Plate Retainers
Tubular type plate retainers are made from porous glass or plastic which is woven or shaped into the form of a round or square tube. A plate is composed of a number of such tubes which are filled with active material in those areas surrounding the conducting cores of the grid. Pasted type plate retainers are added after pasting, typically by wrapping the plate first with fibrous type glass tape or mats and then by a perforated plastic envelope complete with bottom boot or by other suitable filtering systems. All types of retainers act to prevent the escape of positive active material during normal use. Retainers are not needed on negative plates.
MAINTENANCE
RECEIVING THE BATTERY :
Establishing Requirements The number of batteries required for service depends primarily upon the number of 8-hour shifts in effect. Normally, for operation on a single shift basis, the minimum number of batteries required will be the same as the number of items of operating equipment and the batteries need not be removed from the truck for charging. For operation on a 2 or 3 shift basis, the minimum number of batteries required will be twice the number of items of operating equipment and it will, therefore, be necessary to exchange discharged batteries for charged batteries at the end of each work shift. Whenever possible, it is recommended that more than the minimum number of batteries be available for multiple shift operation. This will provide at least 8 hours of rest, after charging, as a cooling period. In an emergency any one battery can be used for two 8 hour shifts during a 24 hour period, but if this is repeated regularly it probably will cause high electrolyte temperatures and could seriously affect service life. Therefore, where 3 shift operation is normal, 3 batteries will be required per item of equipment.
Unpacking Upon Receipt
a. It is important first to examine the exterior of the packing for wet spots on bottom or sides which may indicate leaking jars which could have been broken in shipment. Inspect also for physical damage to battery package which could mean that the battery was affected as well. Report any damage to the superior officer in charge.
b. Make certain that the package is right side up with skid mounts resting firmly on floor.
c. Use a forklift truck or crane of sufficient capacity to remove the packaged battery from the truck or freight car. If a crane is employed be sure the sling is secured against the bottom of the skid and not around the skid mounts.
d. Move the crated battery to the uncrating area and remove packaging, including any wrapping or other protection provided to the battery terminal cable connectors.
e. Inspect battery and report any damage to the superior officer in charge.
f. A properly insulated lifting beam of adequate capacity should be used to lift the battery, by means of an overhead hoist, from the battery skid.
Handling Batteries
At all times, when lifting batteries, use a device which exerts a vertical pull on the lifting eye or tab. If a chain must be used, it should be in combination with a lifting beam with provision for adjusting lifting hook centers to the exact length of the tray. Any method of lifting which tends to “squeeze" or “stretch" the battery tray may distort it and could damage jars or disturb cell seals. A piece of rubber sheet, or other insulating material, temporarily laid on the battery while lifting, will prevent any possible short circuits from chains or hooks. As an additional precaution against accidental shorting, the lifting beam hooks should be electrically insulated from each other.
Preparing Batteries for Use
Batteries are shipped either "charged and dry" or "charged and wet." They vary considerably, of course, in their preparation needs.
Charged and Dry Batteries
Charged and dry batteries are shipped with plates which have been charged and dried, dry separators and without electrolyte in the cells. The vent openings of all cells are sealed and must remain so until the battery is being prepared for service. Charged and dry batteries must be properly activated. Prepare these batteries for use as follows:
(1) Remove all vent caps and destroy the sealing device, red tape or other material used to seal the vent cap holes. Make certain that all vent openings will permit free passage of gas.
(2) Fill each cell to the proper level with electrolyte and having a specific gravity 15 points (.015) lower than the designated fully charged specific gravity unless otherwise specified by the manufacturer.
For example, if the fully charged specific gravity is to be 1.285 the filling acid should be 1.270. Allow the cells to stand for at least several hours after filling, then adjust electrolyte levels so they are 1/4" to 3/8" below the bottom of the vent well or skirt. Replace the vent caps. The temperature of the filling electrolyte must not exceed 90 degrees F.
(3) Clean the cell tops if any electrolyte was spilled. Neutralize with soda solution (one pound of baking soda to one gallon of water), rinse with water and dry thoroughly.
(4) Give the battery a freshening charge. Be sure to continue the charge until the specific gravity remains constant for three consecutive hourly readings.
(5) Recheck electrolyte levels after gassing of electrolyte has stopped and take and record specific gravity reading, electrolyte temperature and open circuit voltage of each cell. If irregularities in specific gravity readings exist, they should be adjusted . Adjust electrolyte levels so they are 1/8" to 1/4" below vent well skirt.
(6) Each battery manufacturer's instructions will provide additional detail. Follow these instructions to assure compliance with any special requirements.
Charged and Wet Batteries
Charged and wet batteries are shipped with cells filled and fully charged. Prepare these batteries for use as follows:
(1) Examine battery to see if electrolyte has been accidentally spilled. If so, clean and neutralize any spillage with a cloth which has been dipped in a soda solution. Rinse with clear water and dry battery thoroughly.
(2) Remove vent caps and check the electrolyte level in each cell. Take and record the specific gravity reading, electrolyte temperature and individual open circuit voltage of each cell. Note any irregularities.
(3) Check to make sure that all cells are properly connected and that terminal connections are tight. If there are irregularities in the electrolyte levels or specific gravity readings or if the battery has been in storage for more than 30 days, it should be given a freshening charge.
(4) Recheck electrolyte levels after charging and after gassing has stopped. Again take and record specific gravity readings and electrolyte temperatures. After the battery has been standing for at least one hour, also take and record the open circuit voltage of each cell. If irregularities in electrolyte specific gravity readings still exist, they should be adjusted.
BATTERY CLEANING:
The modern industrial battery is designed and built to give an average of 1500 cycles of charge and discharge during its life, depending upon the application and the operating environment. The exact length of the service life will depend, to a great extent, upon the care the battery receives. The following maintenance procedures, carried out at the proper time, will do much to prolong the life of the battery and provide efficient, satisfactory service.
Charger Adjustment
Make sure that the charger adjustment, for control of charging rates and cut-off are correct. This will assure that the batteries are properly charged with no excessive over-charge. Batteries that are overcharged regularly will need water more often, and cell temperatures usually will be higher than normal. If either condition is evident, adjust the charge rate downward, in those chargers which have provision for adjustment, so it is between a normal finish rate and one-half normal finish rate. Also check the adjustment of the ampere-hour meter and temperature voltage relay, if either are used, as well as the timer switch.
Cleaning a Battery
Inspect the battery at least once each month to make certain terminal connections are tight. Remove dirt or electrolyte accumulation from the tops of the cells. Wash with clean water and dry. Using a solution of baking soda and water (one pound of baking soda to one gallon of water) neutralize any acid which may be collected at cell or battery terminals to keep them free from corrosion. Use the solution until all fizzing stops. Work the solution under the connectors with a clean paint brush. To remove all traces of soda solution and loose dirt, rinse the battery down with clear water from a low pressure hose. Whenever the battery top is being cleaned or rinsed, vent caps must be tightly in place.
BATTERY GASSING:
Control of Gassing:
Gassing is the evolution of gases from one or more of the electrodes during electrolysis. It is a natural phenomenon which takes place when a battery on charge can no longer accept all of the current being applied to it. Gassing is evidenced by bubbling of the electrolyte. The gases liberated are oxygen, evolved at the positive plates, and hydrogen, evolved at the negatives.
The point at which significant gassing begins is determined by voltage, but the amount of gas depends upon the portion of the charging current that is not being absorbed by the battery. Normally, noticeable gassing will begin when the voltage exceeds 2.30 volts per cell. At 2.40 volts per cell gassing will be normal and at 2.50 it will be rapid. The amperage at which gassing becomes excessive depends primarily upon the state of charge and electrolyte temperatures. As the battery approaches full charge, it is necessary, therefore, to reduce the charging rate to a point at which excessive gassing is prevented. This safe rate is the finishing rate. When proper charging equipment is used the tapering of the charging current to the finishing rate is achieved automatically. Manufacturers instructions will normally prescribe the desired charging rates.
BATTERY WATERING:
Adding Water
A certain amount of water loss in cells is normal and it should be replaced with "pure" tap water or distilled water. In some geographical areas tap water may contain chemicals or other impurities harmful to batteries. The NEMA recommendation for battery replacement water lists the following maximum allowable impurities (parts per million) :
Total solids 350 PPM
Chlorides as C1 25 PPM
Nitrates as NO 3 10 PPM
Iron as Fe 4 PPM
Most industrial truck battery manufacturers provide water analysis service. A minimum sample of one quart is required
Check the height of the electrolyte at least weekly and, if water is needed, add just enough to bring the electrolyte to proper level. Do not overfill. Never fill cells to above the bottom of the vent well or skirt. To avoid overfilling, it is best to add water at the end of a charge.
Water should be added often enough to prevent the electrolyte level from dropping below the perforated separator protector. Ideally a watering schedule should be established. This would assure adequate watering while taking into consideration those factors which control water consumption, such as:
(1) frequency of charging,
(2) water storage capacity of the specific cell type and
(3) age and condition
BATTERY READINGS :
Taking Hydrometer Reading
a. Squeeze the syringe bulb and then slowly release it, drawing into the cylinder or barrel just enough electrolyte to permit the hydrometer float to ride free. The float stem must not touch the side of the cylinder nor the top of the syringe. If the float stem touches the upper area of the syringe, too much electrolyte has been drawn up; if the float still rests on the bottom, too little electrolyte has been drawn up.
b. Read the hydrometer float scale with eye at same level as electrolyte. The reading should be taken at the surface of the liquid disregarding any slight curvature. This reading will be the specific gravity of the electrolyte uncorrected for temperature. See Table 2-2 for correction factors.
c. Return all electrolyte to cell.
Record Keeping
Facilities with more than just a few batteries will find that records of battery cycles, maintenance and repair are indispensable for an effective battery maintenance program. In addition to those monthly records, which require the posting of data each time a battery is charged, the following procedure will be helpful:
a. Establish a battery identification system giving each battery a code number. A multiple-digit system is suggested such as 1201, 1202, etc., for all 12 volt 375 ampere-hour batteries, and 3601, 3602, etc., for all 36 volt 750 ampere-hour batteries etc.
b. Record specific gravity of the pilot cell or cells before and after each charge. Pilot cells should be selected from those nearest the center of the battery and identified by differently colored vent caps. They should be representative of the balance of the cells in the battery.
c. Record the number of cycles on a cumulative basis plus maintenance and repair information. Note any irregularities. The use of a "Battery Cycle and Maintenance Record" form is recommended. If variations in specific gravity readings exceed 20 points (.020) and on-charge voltage, after an equalizing charge, varies by more than .15 volts, contact the manufacturer's service representative.
d. When the battery is new, and on at least an annual basis thereafter, read and record the specific gravity and open circuit voltage for all cells of the battery.
BATTERY OPERATION
Cycling Fundamentals:
A cycle is a discharge followed by a charge. During the charge the electrical energy supplied by the charger causes an electrochemical reaction within the battery. This restores the active materials to a fully charged condition
The Fully Charged Cell or Battery
The positive and negative plates, or electrodes, are separated from each other and immersed in electrolyte. In the fully charged condition the active material of the positive plate is lead dioxide and that of the negative plate is sponge lead. The electrolyte is a solution of sulfuric acid and water that normally varies in specific gravity from 1.275 to 1.295.
The combination produces a voltage of approximately 2 volts on open circuit. This voltage potential results from the fundamental characteristic of a storage battery which dictates that when two electrodes of dissimilar metals are immersed in suitable electrolyte, and a circuit is closed between the two, electrons begin to flow. A fully charged cell should normally have an on-charge voltage of from 2.45 to 2.70 volts when charging at the finish rate.
The Discharging Cell or Battery
While a battery is being discharged or used, lead dioxide and sponge lead combine with sulfuric acid to form lead sulfate within both plates as shown in Figure 1-7. This action causes the specific gravity of the electrolyte to decrease. As the discharge progresses, individual cell and battery voltage declines, generally in direct proportion to the rate of discharge.
The Discharged Cell or Battery
As the depth of discharge increases more sulphuric acid is removed from the electrolyte so the specific gravity decreases and may drop below 1.100 as it approaches the specific gravity of water. Almost all of the active material of both positive and negative plates is converted to lead sulfate as illustrated by Figure 1-8 , and an effective electrochemical reaction is no longer possible. At this point the battery has reached its discharge limit.
The Charging Cell or Battery
The charging action begins when the terminals of the battery are connected to an external source of direct current. The electrochemical reaction is reversed and the positive plates, negative plates, and electrolyte start returning to their original charged condition as indicated by Figure 1-9.
Charging causes the battery voltage to rise as active materials are restored. A cell being charged may have a voltage of from 2.12 to 2.70 volts depending upon charging rate and time.
From the above, it can be seen that storage batteries do not actually store electrical energy. Instead, they accept the electrical energy delivered to them during charging and convert it into chemical energy. During discharging, this chemical energy is reconverted into electrical energy to be used as needed.
As an operating guide, to obtain the best performance and life from a motive power storage battery, the depth of discharge should not regularly exceed 80% of the battery's rated capacity in ampere-hours. It should be charged after each shift of use or whenever the specific gravity of the electrolyte falls below 1.240. It is very important that proper ventilation be provided during charging to make certain that
(1) the hydrogen gas, given off toward the end of the charging process, is dissipated
(2) that individual cell electrolyte temperatures, during normal operations, do not exceed 110 degrees F o.
BATTERY CAPACITY :
Ampere-Hour Capacity
The electrical capability of a storage battery is usually expressed in ampere-hours. The ampere-hour capacity is the number of ampere-hours which can be delivered under specified conditions of temperature, rate of discharge and final voltage. Basically, ampere-hours are determined by multiplying the number of amperes which the battery will deliver by the number of hours during which the current is flowing. Total cell or battery capacity then is determined by the size and number of plates which make up the element. Due to the variety of job requirements batteries are produced with many different sizes of cells.
Voltage
With reference specifically to storage batteries, many "voltage" conditions have been recognized. The most important of these are:
a. Open Circuit Voltage. This is the voltage of a cell or battery at the terminals, when no current is flowing. The nominal open circuit voltage of an individual fully charged cell is 2 volts. This is true regardless of cell size. The voltage of an 18 cell lead-acid battery is stated, therefore, as 36 volts.
b. Initial Voltage . The initial voltage of a cell or battery is the closed circuit voltage at the beginning of a discharge. It is usually taken after current has been flowing for a sufficient period of time for the rate of change of the voltage to become practically constant. This usually occurs within a matter of minutes.
c. Average Voltage. The average voltage of the cell or battery is the average value of the voltage during the period of charge or discharge.
d.Final Voltage. The final or cut-off voltage of a cell or battery is the prescribed voltage at which the discharge is considered complete. It is usually chosen so that the useful capacity of the battery is realized without subjecting it to harmful over-discharging. Final voltage will vary with the rate of discharge, cell temperature and the type of service, but for motive power applications it is considered to be 1.70 volts per cell.
Voltage conditions b, c, and d above are monitored when conducting test discharges. They are essentially academic as regards normal battery usage in a truck.
Rated Capacity
The rated capacity of a storage battery is the number of ampere-hours or watt-hours which it is capable of delivering when fully charged and under specified conditions of temperature, rate of discharge, final voltage and specific gravity. United States industry standards for motive power batteries always specify this to be at the 6 hour rate of discharge. The total capacity available from a battery is greatest at low rates of discharge over a long period of time. Discharging at high current rates reduces the total ampere-hours or watt-hours available.
SULFATION :
This occurs when conditions within the cell cause sufficient accumulation of abnormal lead sulfate at both the positive and negative plates to permanently effect the normal chemical reactions.
Habitual over-discharging below final voltage, prolonged operation in an undercharged condition and extended stand periods while in a discharged state are major causes of sulfation.
A servicing schedule should be followed to provide frequent monitoring and adequate charging. See methods of restoring a sulfated battery.
SERVICE LIFE:
Operating Cycle
An operating cycle of a storage battery is the discharge during use and subsequent charge to restore its initial condition.
Service Life The service life of a storage battery is the period during which it provides useful power while being discharged. It is usually expressed as the time period, or number of cycles, which elapses before the ampere-hour capacity falls below 80% of its rated value. To obtain maximum service life it is recommended that a battery be restricted to one full cycle per 24 hour day or fewer than 300 cycles per year.
Other factors which most often adversely influence service life are:
a. Abnormally high or low electrolyte temperatures.
b. Frequent over-discharging.
c. Failure to add water regularly.
d. Frequent overcharging.
e. Poor, or high, resistance, connections or contacts.
Effect of Temperature
The normal operating characteristics of a storage battery are modified by unusually low or high cell temperatures.
Low Temperatures
Available battery power is reduced by low temperature because electrolyte viscosity and resistance is increased and diffusion throughout the pores of the active material is retarded. For example, a fully charged battery (1.275 to 1.295 specific gravity at 77 degrees F.), when its electrolyte temperature is about 32 degrees F., will deliver only 75% of the capacity which would be available at normal room temperature. This drops to 40% at 0 degreee F. The electrolyte could freeze if a discharged battery was exposed to very cold temperatures for several hours.
In addition to the discharge related problems, the charge acceptance of a lead-acid battery is impaired when electrolyte temperatures drop below 60 degrees F. As a result, batteries should always be kept fully charged, especially in cold weather. They should be heated, even during operation or storage, if exposure is severe enough to cause the temperature of the electrolyte to approach 32 degrees F.
High Temperatures
Although high temperatures, up to 110 degrees F., do not cause a reduction in available capacity, battery operation is adversely effected. Because most chemical reactions are accelerated at high temperatures, the rate of corrosion of the positive grid is increased and the active material is shed more rapidly. Even electrolyte temperatures above 90 degrees F. will cause some reduction in service life and should be avoided whenever possible. Cell temperatures should never be allowed to exceed 110 degrees F.
In the past it was believed that, when batteries were to be used in the tropics, the specific gravity of the electrolyte should be reduced to approximately 1.225.
The battery industry no longer recommends such action. Any advantages which can be related to reducing the specific gravity are more than offset by the problems of
(1) electrolyte adjustment,
(2) identifying such reduction to all battery service personnel so the batteries are properly charged,
(3) greater internal resistance,
(4) reduced cell capacity and
(5) assuring that the higher gravities are again restored if batteries are reshipped to a cold climate where freezing could be a problem
BATTERY CHARGING:
Safety Procedures While Charging Batteries
Specific areas should be designated for charging batteries. These areas should be equipped with overhead hoists, conveyors or cranes for handling batteries.
Charging areas should be adequately ventilated. The actual amount of ventilation will depend upon such factors as number and size of batteries being charged at the same time, room size, ceiling height and air-tightness of the building. Hydrogen concentrations above 4% can be explosive.
Smoking, open flames, and sparks should all be prohibited in the charging area. Post placards for "Hydrogen", "Flammable Gas", "No Smoking" and "No Open Flames”.
Facilities should be provided for flushing and neutralizing spilled electrolyte, for fire protection, including hand operated fire extinguishers, and for protecting charging equipment from damage by trucks, tractors or cranes.
Fresh water should always be available in case electrolyte is splashed on skin, clothing or into eyes. The kinds of equipment available for eye-wash and acid neutralization vary widely but either an eye-wash fountain or deluge shower and chemical burn station (squeeze bottle containing a buffering solution for relief of acid burns) should be located in the immediate work area. These should be clearly identified and readily accessible.
Before connecting a battery to, or disconnecting it from, a charger, the charger should be turned off. Live leads can cause arcing and pitting of battery connector contact surfaces.
Make sure that all electrical connections are tight and mechanically sound to prevent any arcing or loss of power.
Wear a face shield or goggles, rubber gloves, apron and boots when checking, filling, charging or repairing batteries during periods of possible exposure to acid or electrolyte.
When batteries are charged on racks, the racks should be insulated to prevent any possibility of shorting.
When charging an enclosed or covered battery, always keep the battery tray cover, or compartment cover, open during the charging period. This will help to keep the battery cool and disperse the gases.
Keep vent caps in place at all times except while servicing or repairing cells. This minimizes the loss of electrolyte and prevents foreign matter from entering the cells.
Shut off and disconnect both input and output connections to the charger before repairing charging equipment.
When taking specific gravity readings, use a face shield or goggles and read the hydrometer with eye at about the same level as the electrolyte. Return all electrolyte to the cell.
BATTERY REPAIR
SULFATED BATTERY :
In addition to the required routine maintenance, storage batteries may, at some time during their service life, require more extensive or unusual care. Such care should be given as soon as it has been determined that a problem exists or that trouble may be developing. As a result, this section deals with the means of identifying existing or impending problems and offers possible solutions.
If the suggested operational remedies are ineffective, it may be assumed that there is an internal problem and it will be necessary to disassemble the cell or cells to inspect the elements and sediment well. If the cause of the problem can only be corrected by completely rebuilding cells or the battery, this should be reported to the designated person in authority.
Restoring a Sulfated Battery
Undercharging a battery, even to a small degree, if continued, leads to excessive "sulfation." The same is true of batteries which have been left standing in an uncharged state for an extended period. High temperatures rapidly accelerate sulfation when batteries are left standing in a partially charged condition. The cells of a sulfated battery will give low specific gravity and voltage readings. The battery will not become fully charged after a single normal charging when sulfation has taken place over a prolonged period.
If the sulfation has not progressed too far, it may be possible to restore the battery to a serviceable condition by using the following special procedures:
(1) Thoroughly clean the battery
(2) Bring the electrolyte level up to a point which is just visible over the separator protector by adding approved water.
(3) Put the battery on charge at the prescribed finishing rate until the rated ampere-hour capacity has been returned to the battery.
Record the voltage and specific gravity readings. Correct the specific gravity readings for temperature. If the temperature at any time during these procedures exceeds 110 degrees F., stop the charge and allow the battery to cool to 90 degrees F. or below before continuing. Charge the battery until the specific gravity shows no change during a 3 hour period while taking hourly readings. With automatic charging equipment, the battery may have to be placed on equalizing charge two or three times. If a battery is badly sulfated, the specific gravity may rise only 30 to 40 points (.030 to .040) during the first charge.
(4) Place the battery into service and discharge it to a fully discharged condition.
(5) Charge the battery again until the specific gravity shows no change during a 3 hour period.
(6) Repeat the cycling process until the specific gravity rises to within 30 points of a normal fully charged battery, then place the battery back in routine service. Even though specific gravities may be lower than normal they should not vary much from cell to cell. If they do, problems other than sulfation may be present. If the spread between the highest and the lowest gravity reading is 50 points or more, refer to the Troubleshooting Chart, Table 3-1, for help in identifying the problem. If the battery still has not responded to treatment, it should be replaced.
CELL DISCHARGE :
Correcting Excessive Self-Discharge
While a storage battery is in a charged state, a local electrochemical reaction takes place within the cells which causes very gradual discharging. This is known as self-discharge. A small amount is quite normal in motive power batteries where grids are made from antimonial lead. The rate of self-discharge is temperature related, however, and increases significantly as temperatures rise. The normal rate at 77 degrees F. to 80 degrees F. causes a loss in specific gravity of about one point (.001) per day. This becomes of concern only when a wet battery is to be stored for weeks at a time. It can be ignored as a factor in normal battery operation.
It is possible, however, particularly during the latter stages of a battery's life, for the rate of discharge to become much greater and even limit the battery's duty cycle. Excessive selfdischarge may be caused by defective separators or plates which have become shorted at the edges. Edge shorting is usually caused by loss of positive active material which can fill the sediment well or build up on the top or sides of the plates and eventually bridge the space between the positives and negatives. If a shorted condition seems likely, the element should be pulled for examination and the defective separator replaced, shorts cleared or cells replaced. Usually, if the sediment well is full, salvage is impractical.
Test Discharge
A capacity test is sometimes desirable to determine a battery's actual discharge capability as compared to its 6 hour rated capacity. This can be a significant diagnostic tool when equipment does not operate as expected and it can help determine when the battery should be replaced. When a battery consistently delivers less than 80% of its rated ampere-hour capacity, either some cells are sub-standard or it has reached the end of its useful life and should be replaced.
A test discharge is performed by discharging a fully charged battery at a fixed rate under carefully controlled test conditions.
SAFETY
A lead-acid battery can be a very useful, safe source of electrical power. While installing, using, maintaining or repairing a motive power battery, opportunities exist, however, for exposure to potentially dangerous situations. This section identifies those hazards which could result from improper handling or use.
HAZARDS
A SULFURIC ACID solution is used as the electrolyte in lead-acid batteries and has a concentration of approximately 37% by weight of sulfuric acid in water. In this diluted state it is not as hazardous as strong or concentrated sulfuric acid, but it acts as an oxidizing agent and can burn the skin or eyes and destroy clothing made of many common materials such as cotton or rayon.
AN EXPLOSIVE MIXTURE of hydrogen and oxygen is produced in a lead-acid battery while it is being charged. The gases can combine explosively if a spark or flame is present to ignite them. Because hydrogen is so light, it normally rises and diffuses into the air before it can concentrate in an explosive mixture. If it accumulates into gas pockets, as can occur within a cell, it might explode if ignited.
ELECTRICITY is produced by the batteries on discharge and, while most persons cannot "feel" voltages below 35 to 40 volts, all motive power batteries should be regarded as potentially dangerous. A lead-acid battery is capable of discharging at extremely high rates and, under conditions of direct shorting, can cause much damage and serious injury.
THE WEIGHT of these heavy batteries can easily cause painful strains or crushed hands or feet if improperly lifted or handled. Batteries can be damaged if dropped. The average motive power battery weighs more than one ton, so proper equipment must be provided when changing or handling batteries.
BURNS can result from contact with molten lead or hot compound while repairing a battery. Lead can splash when intercell connectors are being re-burned and hot compound can be spilled when resealing covers to jars. The protective gear provided, if worn, will prevent such burns.
SAFETY PROCEDURES WHILE HANDLING BATTERIES
Lift batteries with mechanical equipment only, such as an overhead hoist, crane or lift truck. A properly insulated lifting beam, of adequate capacity, should always be used with overhead lifting equipment. Do not use chains attached to a hoist at a single central point forming a triangle. This procedure is unsafe and could damage the steel tray.
Always wear safety shoes, safety glasses, and a hard hat made of a non-conducting material.
Tools, chains and other metallic objects will be kept away from the top of uncovered batteries to prevent possible short circuits.
Battery operated equipment should be properly positioned with switch off, brake set, and battery unplugged when changing batteries or charging them while in the equipment.
Personnel who work around batteries should not wear jewelry made from a conductive material. Metal items can short circuit a battery and could cause severe burns.
Only trained and authorized personnel should be permitted to change or charge batteries.
Reinstalled batteries should be properly positioned and secured in the truck, tractor or crane.
SAFETY PROCEDURES WHILE CHARGING BATTERIES
Specific areas should be designated for charging batteries. These areas should be equipped with overhead hoists, conveyors or cranes for handling batteries.
Charging areas should be adequately ventilated. The actual amount of ventilation will depend upon such factors as number and size of batteries being charged at the same time, room size, ceiling height and air-tightness of the building. Hydrogen concentrations above 4% can be explosive.
Smoking, open flames, and sparks should all be prohibited in the charging area. Post placards for "Hydrogen", "Flammable Gas", "No Smoking" and "No Open Flames”.
Facilities should be provided for flushing and neutralizing spilled electrolyte, for fire protection, including hand operated fire extinguishers, and for protecting charing equipment from damage by trucks, tractors or cranes.
Fresh water should always be available in case electrolyte is splashed on skin, clothing or into eyes. The kinds of equipment available for eye-wash and acid neutralization vary widely but either an eye-wash fountain or deluge shower and chemical burn station (squeeze bottle containing a buffering solution for relief of acid burns) should be located in the immediate work area. These should be clearly identified and readily accessible.
Before connecting a battery to, or disconnecting it from, a charger, the charger should be turned off. Live leads can cause arcing and pitting of battery connector contact surfaces.
Make sure that all electrical connections are tight and mechanically sound to prevent any arcing or loss of power.
Wear a face shield or goggles, rubber gloves, apron and boots when checking, filling, charging or repairing batteries during periods of possible exposure to acid or electrolyte.
When batteries are charged on racks, the racks should be insulated to prevent any possibility of shorting.
When charging an enclosed or covered battery, always keep the battery tray cover, or compartment cover, open during the charging period. This will help to keep the battery cool and disperse the gases.
Keep vent caps in place at all times except while servicing or repairing cells. This minimizes the loss of electrolyte and prevents foreign matter from entering the cells.
Shut off and disconnect both input and output connections to the charger before repairing charging equipment.
When taking specific gravity readings, use a face shield or goggles and read the hydrometer with eye at about the same level as the electrolyte. Return all electrolyte to the cell.
SAFETY PROCEDURES WHILE HANDLING ACIDS
The splashing of acid into the eyes is the most dangerous condition which can be encountered while handling sulfuric acid or electrolyte. If this should happen, the eyes should immediately be gently flooded with clean, fresh, running water for at least 15 minutes followed as quickly as possible with a physicians examination. If the person is wearing contact lenses they should be removed before rinsing the eyes.
Acid or electrolyte splashed onto the skin should be washed off under running water. Battery electrolyte will usually only cause irritation of the skin; but if a bum develops, it should be treated medically.
When electrolyte is splashed on clothing, use a weak solution of bicarbonate of soda, as soon as possible, to neutralize the acid.
A carboy tilter or safety siphon should be provided for handling acid from a carboy container. Use the protective box when moving a carboy. Store acid in a cool place out of the direct rays of the sun. Use only glass, lead or acid resistant plastic containers when storing acid or electrolyte.
When mixing acid, to prepare electrolyte, always pour the acid slowly into the water and stir constantly to mix well. Never pour water into acid. Never use sulfuric acid solutions which are over 1.400 specific gravity.
Apply a neutralizing solution, such as bicarbonate of soda and water, when acid is spilled on floor and clean up promptly. A mixture of one pound of soda to one gallon of water is recommended. Safety Procedures While Repairing Batteries
Disconnect the battery from the truck, tractor or crane when servicing or repairing either the battery or the equipment. Also make certain the battery is disconnected from the charger before handling or repairing the battery.
Before repairing a battery, remove all of the vent caps and blow out each cell with a low pressure air hose to remove any residual gas. Use only a gentle stream of air to avoid splashing electrolyte
Open or "break" the circuit before repairing damaged or dirty terminal plugs or receptacles connected to a battery, by removing and insulating one terminal lead at a time.
When melting sealing compound, in preparation for resealing cells, be careful not to puncture the top section of unmelted compound with a screw driver or other pointed object. A build-up of pressure from the melted compound in the bottom could cause liquid compound to squirt and inflict a severe burn. Do not allow compound to ignite by overheating. Compound becomes workable at 400 to 425 degrees F.
Check batteries frequently for acid leakage or signs of corrosion.
Use insulated tools whenever possible when working on batteries. If possible, also cover the terminals and connectors of a battery with a sheet of plywood or other insulating material to prevent short circuits.
When taking specific gravity readings, use a face shield or goggles and read the hydrometer with eye at about the same level as the electrolyte. Return all electrolyte to the cell.
BATTERY STORAGE & SHIPMENT - PROCEDURES
Guidelines are provided for those occasions when batteries must be stored, in either a wet or dry state, and for possible reshipment to other areas.
Storage Methods
Charged and Wet Batteries.
Lead acid batteries may be stored in a charged and wet (filled with electrolyte) condition when necessary for periods of up to several months. During such periods they should be stored in a clean, cool, dry and well ventilated location away from radiators, hot air ducts or other sources of heat, and protected from exposure to direct sunlight. Before being stored, the battery should be fully charged and the electrolyte should be brought to the proper level. Any leads should be disconnected or insulated to prevent accidental discharge. The top of the battery must be protected from dust, foreign matter and moisture. Do not attempt to dismantle the battery.
If the average storage temperature is 80 degrees F. or higher, the specific gravity of the electrolyte should be checked at least monthly. If below 80 degrees F., check gravities at least every two months. Whenever the specific gravity, corrected to 80 degrees F., falls to 1.240 or below, the battery should be given a freshening charge. A freshening charge is also recommended just before returning a battery to service.
Charged and Dry Batteries
New batteries are often supplied charged and dry (without electrolyte). Batteries in this condition can remain in storage, unattended, for a period of at least two years. They should be stored in a cool, dry place with vent caps tightly closed. Average temperatures should not exceed 80 degrees F. Batteries should not be stored near radiators, hot air ducts, or other sources of heat, and should be protected from exposure to direct sunlight. The top of the battery should be protected from dust, foreign matter and moisture. Charged and dry batteries when removed from storage should be activated.
Shipment
Charged and Wet Batteries.
Depots or using organizations may make shipments of motive power batteries in a charged and wet condition if intended for use within a period of 90 days. The battery service weight is usually stamped into the steel tray near one of the lifting holes. Detailed battery information may also be obtained from manufacturers catalog.
Before crating a wet battery for shipment it should be given a freshening charge. A tag should be attached to both the battery and the crate showing the date of the last charge and the specific gravity of the electrolyte at the completion of the charge. Make certain that the battery is properly protected when crated. The receiving organization should be alerted also to the need for a freshening charge before the battery is put into service.
Charged and Dry Batteries.
Depots will normally make domestic and export shipments of new batteries which usually will be in a charged and dry condition. Batteries, and the accompanying electrolyte in separate carboys, which are intended for export shipment must be packaged in accordance with approved methods.