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 reinstalled 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 PilotA 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 Charg. 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. See section 1.3.

DD.. 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.

1.3. VOLTAGE READINGSVOLTAGE 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.

A. Each shift(Attendend 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.

B. Whe Tapps 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.

C. During equilizing 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.

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D. 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.

E. Monthly

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

F. Quaterly

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.

1.4 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.

A. Monthly

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

B. 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.

C. Annualy

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

D. After equilizing 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.

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1.5 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.

A. Monthly

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

B. 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.

1.6 CONNECTION RESISTANCE READINGS

A.. 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.

B.. 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.

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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.