MAINTENANCE OF BATTERY

 

Maintenance New Battery Shift Monthly 3-Month Annual 5-Year 

Visual Also See 1.10C &D Flame Inspection Arresters See 1.7 See 8.3 

Battery Float Panel Meter Battery Terminals Compare Panel Voltage Float Voltage with Digital Meter to Digital See 1.3 See 1.3A Voltmeter Voltmeter 

Cell Float All Cells Pilot Cells All Cells Voltages with Digital with Digital with Digital See 1.3 Voltmeter Voltmeter Voltmeter 

Specific Gravity All Cells Pilot Cells 10 Percent of All Cells Readings all Cells See 1.4 

Temperature Pilot Cells 10 Percent of Readings All Cells See 1.5 

Connection All All Connections Resistance Connections See 1.6 

Battery Testing Acceptance Yearly Capacity Capacity See 3.0 Test After Tests if 5-Year Discharge 1 week Test <90 Percent Test 

Check Safety Wash Equipment; Equipment Protective Clothing; See 1.7 & 8.0 Fire Extinguishers, Etc. 

1. CONDENSED INSTRUCTIONS: LEAD-ACID BATTERIES

E1.1 PURPOSE 

The purpose of this section is to outline the duties and responsibilities for routine operation and care of vented lead-acid batteries. Section 2 contains detailed information on lead-acid battery principles. 

11..22 BATTERY CHARGING AND SPECIFIC GRAVITY TEMPERATURE CORRECTION BATTERY CHARGING AND SPECIFIC GRAVITY TEMPERATURE CORRECTION 

AA.. Initial Freshening Charge Initial Freshening Charge 

To establish a reference, give each new battery, or re-installed battery stored for more than 3 months, an initial freshening charge. Use the equalizing voltage given by the manufacturer for the type cell, but do not exceed the maximum voltage of other loads connected to the charger. Apply this charge until each cell gasses freely and equally and specific gravity (sp.gr.) stops rising. Just before the end of the initial charge, record the voltage of each cell. About 20 minutes after the end of the charge, record the specific gravity of each cell, corrected to 77 EF. For every 3 EF above 77EF, add one point (0.001) to the reading. For every 3 EF below 77EF, subtract one point (0.001) from the reading. Use form POM-133A for these records and keep them for the life of the battery. 

—ell.C.1 Pilot A A.1 Pilot Cell.—After the initial charge or to begin a yearly cycle, choose a pilot cell from one of the lowest specific gravity and lowest voltage cells. This cell is used as a representative for readings, for one year. Each year a new pilot cell is chosen. 

eB. Float Charge. B Float Charge 

Charge batteries continuously at the float voltage recommended by the manufacturer. Monthly y take the voltage across the overall battery terminals with an accurate digital meter and compare this reading with the charger and bus voltmeters. If needed, adjust the charger float voltage based on the digital meter. Adjust the charger and/or bus voltmeters to agree with the digital meter if needed. 

A battery is said to float when charging voltage is slightly greater than the open circuit voltage of the battery. Floating current required to keep lead- calcium cells at full charge is about one-fourth to one-third that of lead- antimony cells, but lead-calcium cells usually must be floated at a slightly higher voltage. Lead-selenium cells require float voltages slightly above those of lead-calcium. 

The operation of a battery by float method is based on overall voltage applied to the battery terminals. The voltmeter used must be very accurate. An inaccurate meter can result in either over or undercharge and resulting problems, which reduce life and service of the battery.  

C. C. Equalizing  Charge

The purpose of the equalizing charge is to ensure that every plate in every cell is brought with certainty to a state of full charge by a slight overcharge. 

Do not perform equalizing charges on a routine basis. If one of the conditions below occurs, apply an equalizing charge at the voltage recommended by the manufacturer for the type of cell. Ensure that all cell levels are at the high level mark before beginning the charge. 

1. Following heavy discharge. 

2. If specific gravity (corrected for temperature) of any cell is more than 10 points (0.010) below the full charge value while on float. 

3. If the voltage of any cell is more than 0.04 volt below the average cell voltage when the battery is on float. 

4. If the level in any cell or cells falls at or near the minimum fill line a lot of distilled water must be added to restore the level to the maximum fill line. If this condition occurs, an equalizing charge must be performed to restore specific gravity. 

5. If too little replacement water is being added, typically indicating undercharging (see fig. 1 for typical water consumption). 

Terminate the equalizing charge when all conditions below are met: 

1. Every cell gasses freely and equally. 

2. The specific gravity of all low cells has stopped rising, determined by two specific gravity readings measured over the last one-eighth of the charging period. 

3. The voltage difference between the highest and lowest cells is no greater than at the initial charge. 

Failure to give equalizing charges when needed leads to problems. The ampere-hour capacity of weak cells greatly decreases. During discharge, these cells will be exhausted well ahead of good cells and then become over discharged (see section 2.11) or over sulfated; the plates may buckle, and grids may crack. Continued discharge may reverse the polarity, making positive plates out of the negatives and vice versa, which will destroy the cells. 

If one section of the battery runs warmer than the rest, these cells have a higher rate of internal self-discharge, and capacity gradually falls below the others. Hence, a battery must be located so that sunshine or space heaters do not affect a portion of the battery, which would mask internal self  

discharge temperature increases. 

  

D.. Unattended  Stations

The equalizing charge may be terminated automatically by a timer. Use the manufacturer’s recommended charge time for the cell type. Set the timer to switch off the equalizing charge and to reconnect the float charge. In the event that the manufacturer does not provide a recommended charge time, 3 days (72 hours) may be used as the charge time. 

A "check charge" for batteries at unattended locations may be used to determine if equalization is necessary. With a "check charge,” the battery is placed on charge at the equalizing rate. After allowing 15 or 20 minutes for the rate to stabilize, the voltages of individual cells are measured. If the highest and lowest cell voltages (while on charge at the equalizing rate) differ by no more than 0.04 volt, the battery does not require equalizing. The battery should be equalized if the voltage differences exceed 0.04 volt. Use a digital meter accurate to 0.01 volt. The test described above is effective in determining equality of cell charge. However, the test cannot be substituted for a hydrometer in determining state of charge. All cells must be within 5°F, the reason is described in paragraph 2.6, and the temperature must not be below 55 °F. 

11..33. VOLTAGE READINGS 

Voltage readings should be taken in accordance with the following instructions. NNote: Accurate voltmeters are critical for extending battery life. Provide a digital voltmeter accurate to 0.01 volt reserved only for station battery duty and calibrate it or send it out for calibration at least once a year. This voltmeter must be treated with extra care; do not use a shop meter or electrician’s general-use meter for battery voltages. 

AA.. Each  Shift  ((Attended  Stations))  or  During Routine  Inspections  ((Unattended  Stations))

Check the voltmeter on the control panel to determine if the battery is being charged at the proper voltage. Adjust the battery charging voltage if necessary. 

BB.. When  Taps  Are  Changed

Check the voltage on the control panel when taps are changed on power or station-service transformers. Adjust the battery charging voltage if necessary. 

CC.. During  Equalizing  Charge

Just before terminating the equalizing charge, measure the voltages of the highest voltage cell and the lowest voltage cell of the battery to the nearest 0.01 volt with an accurate digital voltmeter. The equalizing charge should be continued if the voltage difference between the two cells is more than that recorded for the initial charge. 

DD.. Monthly

With the charger in service, check the overall float voltage across the battery terminals with an accurate digital meter and record on form POM-133A. 

EE.. Monthly

Check the pilot cell float voltage with an accurate digital voltmeter and record on form POM-133A. 

FF.. Quarterly

Check the float voltage on all individual cells to the nearest 0.01 volt with an accurate digital voltmeter. Take these readings as rapidly as possible and record them on form POM-133A. At the end of the yearly cycle, use these readings to determine the pilot cells for the next year. 

11..44 SPECIFIC GRAVITY READINGS.

Specific gravity readings of vented lead-acid batteries must be taken in accordance with the following instructions. Note: All specific gravity readings must be corrected to 77EF before recording (see 2.18). Do not attempt to take any specific gravity reading after adding water to a cell. The electrolyte takes several hours to mix after water is added. 

AA.. Monthly

Take the specific gravity reading of the pilot cell and record it on form POM­ 133A. 

BB.. Quarterly

Take specific gravity readings of 10 percent of the total number of cells and record them on form POM-133A. Rotate these cells so that readings are taken on different cells each quarter. 

CC.. Annually

Take specific gravity readings of every cell and record them on form POM­ 133A. 

DD.. After equalizing charge

About 15 minutes after heavy gassing stops, take the specific gravity readings of every cell and record them on form POM-133A. If two cells with the lowest specific gravity (checked over the last one-eighth of the charging period) have not stopped rising, continue the equalizing charge. 

Rev.12/31/97 6 

11..55 TEMPERATURE READINGS

All cells of a battery should be at the same ambient temperature. Heat sources such as sunlight, portable heaters, etc. must be blocked so they do not raise the temperature of individual cells. Record the room ambient temperature before cell temperatures are taken. 

Note: An accurate infrared (IR) camera may be used for temperatures; however, the camera calibration must be checked at least once each year. If possible, take the annual temperature readings of the cells just after camera calibration. If the temperature spread of the cells exceeds 5 °F (i.e., upper rows are warmer) the room ventilation may be inadequate. 

AA.. Monthly

Record the pilot cell temperatures on form POM-133A. 

BB.. Quarterly

Record temperature readings of 10 percent of all the cells; rotate the subject cells each quarter. 

CC.. Annually

If an accurate IR camera is available, take the temperature of the battery connections during a load or discharge test, i.e., while current is flowing. If one or more of the connections are loose or dirty, their temperatures will be higher than the other connections. 

11..66 CONNECTION RESISTANCE READINGS

AA.. After Installation

Using an accurate micro-ohm meter, record the resistance of each connection on form POM-134A. The readings should be on the order of a few micro-ohms (less than 100). Record the readings as a baseline on form POM-134A. For additional information see IEEE 450-1995—Maintenance, Testing , and Replacement of Vented Lead-acid Batteries, Annex D and F. See below for detailed instructions. 

BB..Annually

Repeat resistance checks of the connections checked in step A above and compare values. If any connection resistance has increased more than 20 percent, clean, apply no-ox grease, retorque the connections, and retest. Fill out both “as found” and “as left” columns on form POM-134A. 

Rev.12/31/97 7 

CC.. Recommended Method For Taking Annually Micro-Ohmmeter Readings Across Battery Connections.

Figure 2. - Placement of meter probes for connection resistance measurements. 

Caution: Never place probes across a cell or cells (between positive and negative posts), with the meter set on ohms. The meter may be destroyed and arcing may occur at the battery. 

1. Make sure the battery is on float charge before beginning the readings. Obtain an accurate digital micro-ohmmeter, and set it to the lowest scale. 

2. On cell No. 1 take the first reading between the connector lug and the first post (see fig. 2). This reading will be the resistance between the post and connector lug and will be about one-half the middle readings. Record all readings on form POM-134A. 

3. Take the second reading between opposite polarity posts (not connectors) of cells No. 1 and No. 2. Following readings will be between positive and

negative posts of adjacent cells. These middle readings will include the

resistance of two connections (one on each post) and the intercell

lead(see fig. 2). These readings will be about double the first and last.

4. Take the remaining middle readings as in step 4, proceeding from cell to cell. 

5. Take the last reading between the last post on the last cell and the connector lug as shown. 

6. If high resistance is found, take readings from each post to its connector to determine which of the two connections is bad. Mark this and all high-resistance connections for later repair. 

7. After readings are complete, disconnect the charger and loads from the battery. Caution: do not remove or make connections while current is flowing. Clean problem connections, retorque to manufacturer’s specifications, and apply no-ox grease. Retest the repaired connections and record the resistance in the “as-left” column on form POM-134A. 

Rev.12/31/97 8 

11..77 VISUAL INSPECTIONS

Visual inspections are made to assess the general condition of the battery, battery room, and safety equipment. See below and section 1.10 and record on form 133-A. 

AA..Monthly

Check for general cleanliness of the battery, mounting rack, and battery room. Check for electrolyte leaks and cracks in cells, and take corrective action if any are found. Check for corrosion at terminals, connectors, racks, and cabinets. Check the ambient temperature and make sure ventilation devices (fans and vents) are operable. Check all the electrolyte levels and correct if necessary. 

Check for availability and condition of all safety equipment, gloves, aprons, face shields, etc. (see section 8). Check for a full gallon of labeled neutralizing solution, and operability of eyewash station or portable eyewash equipment. Check for operation and cleanliness of body wash station. Check for a class C fire extinguisher and check that it has been inspected and tested according to schedule. Check for availability of insulated tools and utensils so short circuits can be avoided. Check the hydrometer for cleanliness and cracking of rubber parts. 

11..88 BATTERY  CARE

AA.. Adjustment of Specific Gravity.

Do not add or remove acid in any cell except when following instructions in paragraph 2.17. 

BB.. Temperature

Never intentionally allow electrolyte temperature to exceed 100 EF. 

CC.. Cleanliness 

Keep the battery room or cabinet clean and well ventilated. Keep cells, especially the tops, clean, dry, and free of electrolyte and corrosion residue. 

DD.. Spilled  Electrolyte

At each battery room or cabinet, provide a labeled gallon jar of solution consisting of 1 pound baking soda to 1 gallon of water. Neutralize spilled electrolyte with soda solution, rinse with water, and wipe dry. Do not allow any solution to enter the cells. Keep vent plugs tight and gas vents open. Any missing or worn vent plug gaskets should be replaced. 

11..99 CHARGERS

Rev.12/31/97 9 

Chargers serve two important functions. The main function is to provide d­ c station power and to keep the battery charged. The second function is to be able to replace the battery if the need arises. Two main types available are silicon-controlled rectifier (SCR) and ferro-resonant. The two types differ greatly. SCR chargers consist of a transformer with an SCR bridge and filtering. All control and protection in these chargers is electronic. These chargers are usually the cheapest type because the manufacturer can buy SCRs and electronics “off the shelf.” Ferro-resonant chargers uses a transformer specifically designed for each application. When extreme conditions occur, these transformers saturate and limit, by design, the maximum current and voltage. Additional electronics are not needed. This feature makes the chargers more durable and dependable in a power plant environment. The ferro-resonant type charger is therefore recommended. 

Chargers normally are bought and operated in pairs to share the load. Both chargers operating, with all safety features activated on both, will less likely have a double failure than if one is operating and one is in stand-by mode. In an emergency, a charger on standby trying to power up and assume the duties of a failed charger may exceed its current or voltage limits before safety circuits are enabled. The result may be two failed chargers. The best way to avoid this problem is to operate both chargers in parallel at all times, each supplying half the load. 

The size of the chargers is very important to the life and service of the battery. The chargers must have enough capacity to easily gas the battery under charging conditions. Chargers with too little capacity reduce battery life. A smaller charger, though cheaper initially, can be the most expensive on a long term basis. 

AA.. Every  Shift

Check the panel voltmeter to see if the correct float voltage is being used for charging. 

BB.. Quarterly

Check each charger by turning off one, then the other, and see if each charger will carry the total load. 

CC.Annually

Check the accuracy of the charger panel voltmeter with the digital meter. 

11..1100 RRECORDS

Post a battery data card form POM-157 in a conspicuous location near the battery, and keep accumulated forms in a permanent file. 

Loss of capacity over time is shown by a gradual change in specific gravity of 

Rev.12/31/97 10 

the cells. Keeping accurate records in the battery room is important. Comparison can be made easily between current and earlier readings. A copy of forms POM-133A and POM-134A are included in the forms section and are available from Reclamation’s Technical Service Center in Denver. Four POM-133A quarterly reports and one POM-134A connection resistance report are required for a 60-cell battery each year. Special care is necessary to protect data sheets. Keep current records on clip boards or in a log book near the battery and transfer them to a permanent file at the end of the year.