IEEE Std 1145-1999
(Revision of
IEEE Std 1145-1990)
IEEE Recommended Practice for
Installation and Maintenance of
Nickel-Cadmium Batteries for
Photovoltaic (PV) Systems
Sponsor
IEEE Standards Coordinating Committee 21 (SCC 21) on Fuel Cells, Photovoltaics,
Dispersed Generation, and Energy Storage
Approved 16 September 1999
IEEE-SA Standards Board
Abstract: Safety precautions; installation design considerations; and procedures for receiving,
storing, commissioning, and maintaining pocket- and fiber-plate nickel-cadmium storage batteries
for photovoltaic (PV) power systems are provided. Disposal and recycling recommendations are
also discussed. This recommended practice applies to all PV power systems, regardless of size or
application, that contain nickel-cadmium battery storage subsystems.
Keywords: battery installation, battery maintenance, nickel-cadmium battery, photovoltaic (PV)
power systems
The Institute of Electrical and Electronics Engineers, Inc.
3 Park Avenue, New York, NY 10016-5997, USA
Copyright © 2000 by the Institute of Electrical and Electronics Engineers, Inc.
All rights reserved. Published 07 February 2000. Printed in the United States of America.
Print:
PDF:
ISBN 0-7381-2199-1
ISBN 0-7381-2200-9
SH94841
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Introduction
[This introduction is not part of IEEE Std 1145-1999, IEEE Recommended Practice for Installation and Maintenance of
Nickel-Cadmium Batteries for Photovoltaic (PV) Systems.]
This recommended practice applies to all photovoltaic (PV) power systems, regardless of size or application,
that contain nickel-cadmium battery storage subsystems. The installations addressed herein apply to the
operation of ac, ac/dc, or dc systems that have the battery, PV generating subsystem, and load connected in
parallel. Ideally, the PV generating subsystem should be adequate to supply the normal load and maintain
the battery or batteries in a charged condition. Proper maintenance is required to ensure satisfactory operation, prolong battery life, and aid in determining the need for battery replacement.
Participants
The Storage Systems Working Group of the IEEE Standards Coordinating Committee 21 (SCC 21) on Fuel
Cells, Photovoltaics, Dispersed Generation, and Energy Storage that developed this recommended practice
consisted of the following members:
Jay Chamberlin, Chair
Garth Corey
Tom Hund
James A. McDowell
Ed Mahoney
Larry Meisner
Michael Moore
Arne Nilson
Tom Ruhlman
Stephen Vechy
The following members of the balloting committee voted on this standard:
Mike Behnke
Stephen M. Chalmers
Jay Chamberlin
Richard DeBlasio
Robert Hammond
Stephen J. Hogan
James A. McDowall
Charles Whitaker
John C. Wiles
When the IEEE-SA Standards Board approved this standard on 16 September 1999, it had the following
membership:
Richard J. Holleman, Chair
Donald N. Heirman, Vice Chair
Judith Gorman, Secretary
Satish K. Aggarwal
Dennis Bodson
Mark D. Bowman
James T. Carlo
Gary R. Engmann
Harold E. Epstein
Jay Forster*
Ruben D. Garzon
James H. Gurney
Lowell G. Johnson
Robert J. Kennelly
E. G. “Al” Kiener
Joseph L. Koepfinger*
L. Bruce McClung
Daleep C. Mohla
Robert F. Munzner
Louis-François Pau
Ronald C. Petersen
Gerald H. Peterson
John B. Posey
Gary S. Robinson
Akio Tojo
Hans E. Weinrich
Donald W. Zipse
*Member Emeritus
Also included is the following nonvoting IEEE-SA Standards Board liaison:
Robert E. Hebner
Janet Rutigliano
IEEE Standards Project Editor
Copyright © 2000 IEEE. All rights reserved.
iii
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Contents
1.
Overview.............................................................................................................................................. 1
1.1 Scope............................................................................................................................................ 1
1.2 Purpose......................................................................................................................................... 1
2.
References............................................................................................................................................ 1
3.
Definitions............................................................................................................................................ 2
4.
Safety ................................................................................................................................................... 2
4.1 Safety equipment ......................................................................................................................... 2
4.2 Hazards and precautions .............................................................................................................. 2
5.
Receiving and storage .......................................................................................................................... 4
5.1 Receiving inspection.................................................................................................................... 4
5.2 Unpacking Inspection .................................................................................................................. 4
5.3 Storage ......................................................................................................................................... 5
6.
Installation design ................................................................................................................................ 5
6.1 Enclosure...................................................................................................................................... 5
6.2 Battery support structure.............................................................................................................. 6
6.3 Seismic......................................................................................................................................... 6
6.4 Electrical ...................................................................................................................................... 7
7.
Installation procedures ......................................................................................................................... 7
7.1 Battery support structure assembly.............................................................................................. 7
7.2 Battery activation ......................................................................................................................... 7
7.3 Battery mounting and connections............................................................................................... 8
8.
Commissioning .................................................................................................................................... 8
8.1 Pre-operational checks ................................................................................................................. 8
8.2 Initial charging procedure ............................................................................................................ 9
8.3 Final connections ......................................................................................................................... 9
9.
Maintenance and inspections ............................................................................................................... 9
9.1 General......................................................................................................................................... 9
9.2 Inspections ................................................................................................................................... 9
9.3 Corrective actions ...................................................................................................................... 10
iv
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10.
Reapplication, recycling, and disposal............................................................................................... 11
10.1 Reapplication ............................................................................................................................. 11
10.2 Recycling ................................................................................................................................... 11
10.3 Disposal...................................................................................................................................... 11
Annex A (informative) Bibliography............................................................................................................. 12
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IEEE Recommended Practice for
Installation and Maintenance of
Nickel-Cadmium Batteries for
Photovoltaic (PV) Systems
1. Overview
1.1 Scope
This recommended practice provides safety precautions, installation design considerations, and procedures
for commissioning, maintenance, and storage of pocket and fiber-plate nickel-cadmium storage batteries for
photovoltaic (PV) power systems. Disposal and recycling recommendations are also discussed.
While this document gives general recommended practices, battery manufacturers can provide specific
instructions for battery installation and maintenance.
1.2 Purpose
This recommended practice is meant to assist nickel-cadmium battery users with properly storing, installing,
and maintaining nickel-cadmium batteries used in residential, commercial, and industrial PV applications.
2. References
This recommended practice shall be used in conjunction with the following publications. Additional sources
of information are provided in Annex A.
IEEE Std 100-1996, IEEE Standard Dictionary of Electrical and Electronics Terms, Sixth Edition.1
NFPA 70-1999: National Electrical Code®, (NEC®).2
1IEEE
publications are available from the Institute of Electrical and Electronics Engineers, 445 Hoes Lane, P.O. Box 1331, Piscataway,
NJ 08855-1331, USA (http://www.standards.ieee.org/).
2NFPA publications are published by the National Fire Protection Association, Batterymarch Park, Quincy, MA 02269, USA (http://
www.nfpa.org/). Copies are also available from the Sales Department, American National Standards Institute, 11 West 42nd Street, 13th
Floor, New York, NY 10036, USA (http://www.ansi.org/).
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IEEE
Std 1145-1999
IEEE RECOMMENDED PRACTICE FOR INSTALLATION AND MAINTENANCE OF
3. Definitions
The following definitions apply specifically to this recommended practice. For other definitions, see
IEEE Std 100-1996.3
3.1 life: The period during which a fully charged battery is capable of delivering at least a specified percentage of its rated capacity.
3.2 rated capacity (C): The capacity assigned to a cell by its manufacturer for a given discharge rate, at a
specified electrolyte temperature and specific gravity, to a given end-of-discharge voltage.
4. Safety
The safety practices listed herein should be followed during battery installation and maintenance. Work performed on batteries shall be done with the proper tools and protective equipment. Battery installation shall
be performed or supervised by personnel knowledgeable of batteries and the required safety precautions.
Keep unauthorized personnel away from batteries.
4.1 Safety equipment
The following equipment is recommended for safe handling of batteries and protection of personnel:
a)
b)
c)
d)
e)
f)
g)
Full eye protection such as goggles and/or face shield;
Protective, long-sleeved clothing, including rubber or plastic gloves, aprons, and overshoes;
Portable or stationary safety shower and eye wash stations;
Lifting device of adequate capacity;
Tools with insulated handles;
Class C fire extinguisher (CO2 type should not be used because of the potential thermal shock to
batteries);
Electrolyte neutralizing agent.
4.2 Hazards and precautions
The following are hazards inherent in the use of nickel-cadmium batteries. The recommended precautions
will help to ensure safety while batteries are installed and maintained.
4.2.1 Electrolyte
The alkaline electrolyte is a dilute solution of potassium hydroxide in water. Potassium hydroxide is a strong
caustic agent and is harmful to the eyes and skin. These procedures should be followed:
a)
Wear full eye protection and protective clothing.
b)
If electrolyte contacts the eyes, flush immediately with water for 15 min and obtain medical
attention.
c)
If electrolyte is splashed on the skin or clothing, wash it off immediately with water for 10–15 min.
3Information
2
on references can be found in Clause 2.
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NICKEL-CADMIUM BATTERIES FOR PHOTOVOLTAIC (PV) SYSTEMS
IEEE
Std 1145-1999
d)
Spilled electrolyte should be flushed off with water. A common practice is also to use a 10% solution
of boric acid to neutralize the electrolyte. The resulting liquid should be flushed with water. This liquid may be considered hazardous waste and should be treated accordingly.
e)
Properly dispose of unused electrolyte and electrolyte containers. These are considered hazardous
waste and should be treated accordingly.
f)
Do not use hydrometers and thermometers that have been used with lead-acid batteries. Mixing of
acidic and alkaline electrolytes can cause a violent reaction and permanent damage to the battery.
4.2.2 Electrical
A battery can present an electrical shock and short-circuit hazard. These procedures should be followed:
a)
b)
c)
d)
e)
Remove rings, wristwatch, other metal objects, and articles of clothing with metal parts that might
come in contact with battery terminals and other live parts.
Wear rubber or plastic gloves and boots of adequate electrical insulation, particularly for systems
above 48 V.
Use tools with insulated handles.
Disconnect charging source and load prior to opening or closing any other battery connections.
Determine if the battery is inadvertently grounded, and if so, remove the source(s) of ground (for
example, electrolyte spillage). Contact with any electrically conductive path of a grounded battery
can result in electrical shock. The likelihood of shock can be reduced if inadvertent grounds are
removed.
4.2.3 Fire
A battery can present a fire hazard because it produces flammable gas during the last portion of charging and
is capable of producing high currents. These procedures should be followed:
a)
b)
c)
d)
e)
f)
g)
h)
i)
Provide ventilation in accordance with 6.1.3.
Prohibit smoking in the battery area.
Keep the battery area free from open flames and arcs.
Prior to working on a battery, discharge any possible static electricity from body or clothing by first
touching an earth-grounded part.
Install flame arrestor vents or gas recombination vent caps in accordance with the battery manufacturer’s recommendations.
Do not adjust connections or terminals while charging.
Ensure that no flame or spark can be produced close to the cells, and particularly in the vicinity of
the cell filler caps where gas escapes.
Follow proper installation procedures (see Clause 7).
Maintain battery and connections in accordance with Clause 9.
4.2.4 Shipping and handling
These safety procedures should be followed prior to and during installation:
a)
b)
c)
Inspect all lifting devices for functional adequacy and use them properly.
Do not overturn the shipping package.
In the case of rack mounting, completely assemble and tighten racks before loading cells, and load
the racks in accordance with the manufacturer’s recommendations.
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IEEE
Std 1145-1999
d)
IEEE RECOMMENDED PRACTICE FOR INSTALLATION AND MAINTENANCE OF
Prevent impact of cells to avoid damage and electrolyte spillage.
4.2.5 Other
The following are general safety precautions:
a)
b)
c)
d)
Ensure unobstructed egress from the battery area.
Prevent unauthorized access to the battery area.
Keep top of battery clear of all tools and other foreign objects at all times.
Ensure that appropriate warning signs are prominently displayed in the battery area.
5. Receiving and storage
5.1 Receiving inspection
The nickel-cadmium battery is normally shipped with the cells either filled with electrolyte and charged, or
discharged with the electrolyte removed. In the latter case, the electrolyte, either in a dry or liquid form, is
packaged separately. These procedures should be followed:
a)
b)
c)
d)
e)
Upon receipt, inspect the shipment for possible damage in transit.
Note shipping date; unpack the battery immediately upon arrival.
Make sure that no small package is discarded with the packing material.
If electrolyte has leaked, take necessary precautions consistent with 4.2.1.
Record receipt date and inspection data.
5.2 Unpacking Inspection
After unpacking the battery, inspect the cells for damage. Any damaged unit should be replaced.
WARNING
The battery must never be charged with the transportation seals in place. Doing this can cause permanent cell damage.
5.2.1 Filled Cells
If the cells are shipped with transportation seals, the seals must be removed before putting the battery into
service. Use caution in removing seals because gas pressure can build up in the cells.
a)
b)
Check electrolyte levels to determine if the cells are filled according to the manufacturer’s recommendation. If the electrolyte level is below the top of the plates, the cell has probably been inverted
in transit. It will then be necessary to replace the spilled electrolyte.
Minor differences in the electrolyte level will generally vanish in several hours.
5.2.2 Unfilled cells
The cells are shipped with transportation seals. These should be left in place and removed just prior to filling
the cells.
4
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NICKEL-CADMIUM BATTERIES FOR PHOTOVOLTAIC (PV) SYSTEMS
IEEE
Std 1145-1999
Inspect the electrolyte packaging material for damage. If damaged, electrolyte packages require replacement. Dry electrolyte is contaminated by prolonged exposure to air.
5.3 Storage
It is recommended that the site construction schedule allow for battery installation shortly after delivery. If
storage of the battery is required, these practices should be followed:
a)
b)
c)
The battery should be stored indoors in a clean, cool, and dry area. Temperature extremes and localized heat sources, such as radiators or direct sunlight, should be avoided.
Do not double-stack pallets or store anything on top of batteries, as this may result in damage.
If the battery is to be in storage for less than one year, it can be stored filled and fully charged. When
the battery is to be put into service, follow the procedure for commissioning (see Clause 8).
6. Installation design
Considerations to be addressed in the design of a PV battery installation depend on the size and operational
requirements of the PV system of which the battery is a part. The following are general criteria for all PV
battery installations.
6.1 Enclosure
The battery should be protected by means of a suitable enclosure. This may vary from a box to a room. It
should be clean, dry, adequately ventilated, and should provide protection against detrimental environmental
conditions. Consideration should be given to allowances for future system expansion.
6.1.1 Location
a)
b)
The battery enclosure should be located as close as practical to the PV array, loads, and power conditioning equipment, as specified in 6.1.3.
The enclosure location should provide adequate structural support.
6.1.2 Mechanical considerations
a)
The enclosure should allow for sufficient clearance around the battery to provide access for installation and maintenance. Consideration should be given to the space required for safety and handling
equipment (see 4.1).
b)
The supporting surface of the enclosure should have adequate structural strength to support the battery weight and its support structure.
c)
The enclosure should be resistant to the effects of the alkaline electrolyte through the use of either
appropriate materials or coatings. Examples of appropriate materials are steel, wood, and plastics
such as polyethylene and polypropylene. Epoxy can be used for coatings. Materials to be avoided
are aluminum, copper, and galvanized steel. Provision should be made for containment of any
spilled or leaked electrolyte.
d)
Enclosure doors should allow unobstructed egress.
e)
The enclosure design should include appropriate means to prevent unauthorized entry.
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IEEE
Std 1145-1999
IEEE RECOMMENDED PRACTICE FOR INSTALLATION AND MAINTENANCE OF
6.1.3 Environmental considerations
a)
Nickel-cadmium batteries produce hydrogen during the final stages of charging. The maximum
hydrogen production rate per cell is
H = 1.27 × 10–7 × I
where
H is the hydrogen generation rate in cubic meters per second;
I is the cell charge current in amperes.
If allowed to accumulate, a potentially explosive mixture could result. Natural or forced ventilation
of the enclosure shall be provided to keep the hydrogen concentration to less than 2% by volume.
The enclosure design should either avoid creation of difficult-to-ventilate areas, including false ceilings, or make adequate provision for their ventilation. The battery manufacturer should be contacted
for advice on adequate ventilation. While nickel-cadmium batteries produce hydrogen, they do not
give off corrosive gases; therefore, they can be installed with other equipment when adequate
hydrogen ventilation is provided.
b)
A maximum electrolyte temperature is specified by the battery manufacturer. Extremely high electrolyte temperatures may cause excessive water usage and may damage the battery. Either a passive
or active means to reduce excessive electrolyte temperature should be considered. Passive means
include burial of enclosures, color of exterior finish, and insulation. Active means include forced air
ventilation. Since nickel-cadmium batteries are not damaged by freezing temperatures, special precautions for low temperatures are not required.
c)
Localized heat sources, including direct sunlight, radiators, steam pipes, and space heaters, should
be avoided. Batteries with plastic cell cases should not be exposed to direct sunlight for a lengthy
period of time to avoid degradation of the plastic due to ultraviolet light.
d)
Illumination of enclosures during time of maintenance should be adequate for the safety and effectiveness of personnel. See the IES Lighting Handbook [B5].
6.2 Battery support structure
The battery support structure may consist of racks or other means for supporting the battery within the
enclosure, and it should
a)
b)
c)
d)
e)
Provide suitable strength to support the battery;
Provide space required for maintenance;
Be resistant to alkaline electrolyte;
Provide electrical isolation for cell case and battery. Any insulating material used should be rated for
full system voltage;
Provide space between the cells for air circulation, as required by the manufacturer.
6.3 Seismic
The cells should be installed in a manner consistent with expected seismic events. The battery manufacturer
can provide recommendations and racks designed for seismic protection.
6
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NICKEL-CADMIUM BATTERIES FOR PHOTOVOLTAIC (PV) SYSTEMS
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Std 1145-1999
6.4 Electrical
a)
Bare terminals, lugs, and other live parts should be insulated to reduce the risk of fire as well as
shock and burns to personnel.
b)
Electrical cabling should not obstruct access space provided for maintenance and safety, and should
not impose undue stress to cell terminals.
c)
Electrical cabling losses (due to size and length) should not exceed allowable system values.
d)
All battery systems should be provided with fault and overcurrent protection, and with disconnecting
means for both the positive and negative terminations. This requirement also applies to all instrumentation and control leads connected to the battery system. When parallel cell strings are used, the
need for fault and overcurrent protection of the individual strings should be considered.
e)
Equipment with arcing contacts should not be located where explosive hydrogen concentrations
could occur [see 6.1.3, item (a)]
f)
Consideration should be given to providing instrumentation and alarm functions. These can include
1)
2)
3)
4)
Voltmeter;
Ammeter;
High- and low-voltage indicators;
Ground fault detector and indicator.
7. Installation procedures
7.1 Battery support structure assembly
Battery support structures should be designed and constructed to support the weight of the battery and withstand expected seismic events. The assembly of the support structures should be in accordance with the
manufacturer’s recommended procedure. When there is a risk of movement, secure the support structure to
its foundation.
7.2 Battery activation
Batteries may be shipped with the cells either filled with electrolyte and charged, or discharged with the
electrolyte removed. A filled and charged battery is ready for installation. An unfilled and discharged battery
requires activation before installation, as follows:
a)
Do not remove the plastic transportation seals until ready to fill the battery.
b)
If the electrolyte is shipped in liquid form, fill the cells with electrolyte to the maximum recommended level.
c)
If the electrolyte is shipped in dry form, dissolve the dry electrolyte in distilled or deionized water
according to the manufacturer’s recommendations. (Pure rain water may be used if recommended or
approved by the manufacturer.) Use only clean vessels of plastic or stainless steel. Copper, aluminum, or galvanized vessels shall not be used. Stir with a plastic or stainless steel paddle until the dry
electrolyte is entirely dissolved. The solution will become hot. After cooling to 25 °C (77 °F), adjust
the specific gravity to the value recommended by the manufacturer by adding water. Fill the cells
with electrolyte to the maximum recommended level.
NOTE—To avoid excessive heating, always add dry electrolyte to water; never add water to dry electrolyte.
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IEEE
Std 1145-1999
IEEE RECOMMENDED PRACTICE FOR INSTALLATION AND MAINTENANCE OF
7.3 Battery mounting and connections
Although various methods of interconnecting cells are used, the following procedures apply generally to all
methods of interconnection. However, individual steps should be modified, where necessary, to be consistent
with the battery manufacturer’s instructions.
a)
For multilevel support structures, it is important to maintain stability during installation. It is generally recommended that cells be placed on the support structure starting at the center of the lowest
level, and working outward and upward. Cells should not be slid across rough surfaces nor
lubricated on the bottom surface to aid sliding, because case damage may occur.
b)
The cell terminals may be shipped coated with corrosion-inhibiting grease. Clean any area showing
evidence of corrosion or dirt. Do not use a wire brush or solvents other than those recommended by
the manufacturer. Recoat cleaned area with a thin film of the manufacturer’s recommended
corrosion-inhibiting grease.
c)
If potassium carbonate crystals (gray-white deposits) have formed on the top of a cell, rub with a
soft brush and rinse with water. Vent caps can be removed and rinsed in water. The resulting liquids
are considered hazardous waste and should be treated accordingly.
d)
Install flame-arresting vent assemblies as required.
e)
Measure the voltage and check the polarity of each individual cell or cell block in the battery against
the design. Correct discrepancies as required.
f)
Ensure that all terminal posts and intercell connector contact surfaces are clean, and then apply a
thin film of corrosion-inhibiting compound to all contact surfaces.
g)
Interconnect cells so as to make series, parallel, or series-parallel connections in accordance with the
system design. Interconnecting cables should be pre-bent prior to installation. In general, all series
connections should be made prior to parallel connections.
h)
With the cells properly aligned, tighten connections (including factory-made connections) to the battery manufacturer’s recommended torque value.
i)
If necessary for future reference, apply individual cell identification numbers in sequence, beginning
with number one on the cell at the positive terminal of the battery. Also add any required warnings
and instructions.
8. Commissioning
8.1 Pre-operational checks
a)
Measure the voltage of the battery to ensure that individual cells are connected correctly; that is, the
total voltage should be approximately equal to the number of cells in series times the measured voltage of one cell. If the measurement is less, correct discrepancies as required.
b)
Clean all cell covers and containers. Use a water-moistened clean wiper to remove dust and dirt. All
wipers should be free of oil, distillents, or solvents. The wiper may be considered hazardous waste
and should be treated accordingly.
c)
Perform visual inspection of completed battery installation to verify the following:
1)
2)
3)
8
Proper assembly in accordance with electrical and mechanical design;
Integrity of all components;
Cleanliness and installation in accordance with good workmanship practices.
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NICKEL-CADMIUM BATTERIES FOR PHOTOVOLTAIC (PV) SYSTEMS
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Std 1145-1999
8.2 Initial charging procedure
Apply an initial charge to bring the battery to a fully charged condition and to ensure that all cells are equally
charged. Cells shipped filled with electrolyte and charged require recharging to compensate for the
self-discharge loss occurring during their shipping and storage period. Cells shipped discharged and with
the electrolyte removed require a complete charging.
In general, it is preferable to give a nickel-cadmium battery too much charge rather than too little. The only
disadvantage is an increase in water consumption.
a)
The initial charging of the battery can be made from the PV array or any available appropriate dc
power source. Longer charging periods may be necessary when using the PV array. The continuous
charging current, in amperes, should not exceed 0.20 times the 100 h rate.
1)
A battery shipped filled with electrolyte and charged should be recharged 0.05 (5%) times its
100 h capacity for each month since its last full charge.
2)
A battery shipped discharged and with the electrolyte removed should, after electrolyte filling
(see Clause 7), be charged 2.0 (200%) times its 100 h capacity.
b)
Unless otherwise specified by the battery manufacturer, if any cell temperature exceeds 54 °C
(130 °F) interrupt or reduce the charge until the temperature has dropped to 38 °C (100 °F), at which
time charging may be resumed.
c)
After the initial charge is completed, adjust the electrolyte level to the maximum recommended by
the manufacturer using water of the quality specified.
8.3 Final connections
When all installation procedures have been satisfied, complete the system connections.
9. Maintenance and inspections
9.1 General
Proper maintenance will prolong the life of a battery and will help ensure that it is capable of satisfying its
design requirements. A good battery maintenance program will serve as a valuable aid in determining the
need for battery replacement. Only personnel who are familiar with battery installation, charging, and maintenance procedures shall be permitted unescorted access to the battery area. The safety practices of Clause 4
should be followed.
9.2 Inspections
The results of all inspections should be recorded. Adequate battery records (maintenance procedures, environmental problems, system failures, and any corrective actions taken) are an invaluable aid in determining
the condition of the battery.
It is preferable that all inspections be made on a fully charged battery. The inspection schedule that follows
is recommended for good maintenance.
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IEEE
Std 1145-1999
IEEE RECOMMENDED PRACTICE FOR INSTALLATION AND MAINTENANCE OF
9.2.1 Initial readings
The initial readings should be taken at the time the battery is placed in service. The following readings
should be taken on a fully charged battery with no load on the system:
a)
b)
c)
d)
Battery terminal voltage and cell voltages (preferably taken with the battery on charge; record charging current);
Cell electrolyte levels;
Internal temperatures of 10% of the cells chosen at random (record ambient temperature);
Monitoring the water consumption during the first few weeks of use is recommended to determine
the frequency of water addition. A need for adding water more frequently than semiannually may
indicate excessive battery charging. In this case, system sizing and/or charge controller set points
should be reviewed.
9.2.2 Semiannual inspection
Perform the following inspections on a semiannual basis:
a)
b)
c)
d)
e)
f)
g)
General appearance and cleanliness of the battery and battery area;
Battery terminal voltage and charging current;
Electrolyte levels;
Cracks in battery cases or leakage of electrolyte;
Ambient temperature;
The adequacy of the ventilation system, if installed;
Evidence of current leakage to ground.
9.2.3 Annual inspection
Perform the following inspections on an annual basis:
a)
b)
c)
Battery terminal voltage and cell voltage;
Electrolyte temperature of 10% of the cells chosen at random;
Integrity of battery support structure and enclosure.
9.3 Corrective actions
9.3.1 Routine actions
The following conditions should be corrected at the time of inspection:
10
a)
Correct low electrolyte levels and record amount of water added. Water should be added to bring all
cells to the high electrolyte level. Water quality should be in accordance with the manufacturer’s
instructions. When adding water, take care it is not spilled on cells or support structures. After filling,
carefully dry any parts that may have become wet.
b)
Carefully examine flexible cable connections and replace cables if the insulation is damaged.
c)
If the electrolyte temperature of any cell is outside the design limits, determine the cause and
correct it.
d)
Remove excessive dirt or spilled electrolyte in accordance with 8.1, item (b).
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NICKEL-CADMIUM BATTERIES FOR PHOTOVOLTAIC (PV) SYSTEMS
IEEE
Std 1145-1999
e)
If potassium carbonate crystals (gray-white deposits) have formed on top of a cell, remove them in
accordance with 7.3 item (c).
f)
Correct any other abnormal conditions according to the manufacturer’s recommendations.
9.3.2 Aging battery actions
When the battery is over eight years old, the electrolyte specific gravity should be monitored annually. If a
significant drop in specific gravity (0.03) is noticed between the initial and annual readings, contact the battery manufacturer for recommended corrective actions. A drop in the specific gravity can cause a reduction
in performance and battery life if not corrected.
10. Reapplication, recycling, and disposal
All batteries have a useful life and, eventually, must be either repaired or scrapped. The constituents of the
nickel-cadmium cell, such as the caustic potassium hydroxide electrolyte and the toxic cadmium metal are
hazardous. Therefore, a nickel-cadmium battery that is not of any use or value shall be disposed of in a
proper fashion.
10.1 Reapplication
Nickel-cadmium batteries retain their ability for service, albeit at a lower capacity level, for many years.
Therefore, when they reach the end-of-service life in a particular application, they may be used in another
application whose requirements are met by the lower capacity. Pocket-plate batteries may require replacement of the electrolyte at this time.
10.2 Recycling
The potassium hydroxide electrolyte can be purified for use in new batteries. The cadmium and nickel can be
recycled. Seek advice from the battery manufacturer on how to proceed with battery recycling.
10.3 Disposal
Recycling of nickel-cadmium batteries, rather than their disposal, is recommended. Contact the battery
manufacturer for information on recycling procedures. When a battery is to be disposed of, all government
(local, state, and federal) regulations for such disposal shall be followed. The local hazardous waste management branch may give information on how to proceed with respect to applicable regulations.
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IEEE
Std 1145-1999
Annex A
(informative)
Bibliography
[B1] IEEE Std 928-1986 (Reaff 1991), IEEE Recommended Criteria for Terrestrial Photovoltaic Power Systems.
[B2] IEEE Std 929-1988 (Reaff 1991), IEEE Recommended Practice for Utility Interface of Residential and
Intermediate Photovoltaic (PV) Systems.
[B3] IEEE Std 1106-1995, IEEE Recommended Practice for Maintenance, Testing, and Replacement of
Nickel-Cadmium Storage Batteries for Generating Stations and Substations.
[B4] IEEE P1115/D4, September 1998, Draft Recommended Practice for Sizing Nickel-Cadmium Storage
Batteries for Stationary Applications.
[B5] IESNA Lighting Handbook, Ninth Edition.4
4IESNA publications are available from the Illuminating Engineering Society of North America, 120 Wall Street, 17th Floor, New York,
NY 10005, USA (http://www.iesna.org/).
12
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