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MONITORING OF VRLA BATTERIES GUIDELINES
No. GL/BAT-04/02 MAR 2007
This document supersedes the previous document " Monitoring of VRLA Batteries Guidelines No. GL/BAT- 03/01JUN 2003"
TELECOMMUNICATION ENGINEERING CENTRE KHURSHIDLAL BHAWAN, JANPATH, NEW DELHI-110001 (INDIA)
All rights are reserved and no part of this publication may be reproduced, stored in any retrieval system, or transmitted, in any form or by any means, electronic, mechanical, photocopying, recording, scanning or otherwise without written permission from the Telecommunication Engineering Centre, New Delhi-110001.
Issued GL/BAT-03/01JUN 2003 Monitoring of VRLA Batteries Guidelines GL/BAT-04/02 MAR 2007 Monitoring of VRLA Batteries Guidelines
Remarks First issue
Second issue To incorporate major changes in technology part and addition of problems and solutions.
PART 1 : Technical Requirements (VRLA Battery Technology, Problems and Solutions) 1.0 1.1 1.2 1.3 1.4 1.5 1.6 Scope 1 Introduction 1 Failure of VRLA batteries 4 Factors leading to the premature failure and affecting the 7 life & performance of the battery Options for recoupment of battery capacity and their impacts 14 Monitoring of VRLA Batteries 19 Monitoring Schedule 24
PART 2 : General Requirements ( Planning of VRLA Batteries) 2.0 2.1 2.2 2.3 Planning of VRLA Batteries Battery bank as per Load & Back-up requirements Sample Calculations for Battery bank Disposal of unserviceable Batteries Terminology Abbreviations 25 25 28 30 31 36
1. BIS 1651 : Stationary cells and batteries. 2. BIS 1554 with amendment-I (1994) : Fire Retardant Cables. 3. GR/BAT-01/03 MAR 2004 with amendments if any : VRLA Batteries 4. GR/BAT-02/02 MAR 2006 with amendments if any : VRLA Batteries for High Rate of Discharge ( UPS) Application. 5. GR/BAT-03/01 MAR 2006 Tubular VRLA Batteries based on GEL Technology. 6. GR/SMP-01/05 JAN 2005 with amendments if any : SMPS based Power Plants. 7. Maintenance free Batteries by D Berndt. 8. Battery Reference Book by T.R. Crompton. 9. Modern Battery Technology Edited by Clive D.S. Tuck. 10. Battery Technology Hand-book Edited By H.A. Kiehne. 11. QM-333 : Specification for Environmental Testing of Electronic Equipments for Transmission and Switching use. 12. QM-115 : Quality standard for calculation/verification of MTBF 13. IS 1554 with amendment-1 (June 1994) : Standard for Cables & Wires 14. ITU-T Rec. 0.41 : Psophomeric noise requirements.
PROBLEMS AND SOLUTIONS)
GL No. GL/BAT-04/02 MAR 2007
(VRLA BATTERY TECHNOLOGY.
1. VRLA batteries require very little maintenance. also known as boostcharging. that is why they are confused as “maintenance free batteries”. These batteries also require periodical special charging process at comparatively higher voltage of 2. This is because of the fact that these batteries do not require the rigid routine maintenance like periodic topping up. hence assembly and charging at site is essential. It has also given the guidelines for calculating load for a given system.7V/cell (a total voltage of 65 V). as well as to reduce sulpahtion of plates. the Department has been procuring VRLA batteries for the purpose. Since then. Moreover the Conventional lead acid (Flooded type) batteries which were being used in the department were bulky and required a separate battery room with exhaust fans to throw out the acid fumes emitted by these batteries. These guidelines have detailed the facts which shall be taken into consideration while selecting a Battery for a given requirements.0
Scope This document covers the basic theory and concept of VRLA Batteries technology. In 1994 the VRLA batteries were introduced in Indian Telecom Network for the first time. Till 1994. the battery under boost-charging and the charger have to be isolated from the exchange equipment. to agitate the electrolyte thoroughly to prevent stratification of electrolyte. These batteries emit extremely low amount of gases and do not require periodic toping up. In the initial stages of standby power source. All these batteries were being procured and tested as per respective IS standard IS-1650.MONITORING OF VRLA BATTERIES GUIDELINES
GL/BAT-04/02 MAR 2007
. the whole of the Indian Telecom Network relied wholly on Flooded type batteries to provide the necessary power back-up. issued by Ministry of Environment and Forest. Sample calculation for deciding the load and Batteries have also been incorporated in this document to elaborate the guidelines for the user. It also covers the necessary guidelines for planning of the Batteries for a given telecom equipment. Hence. The certification of these batteries was being done by QA wing of DoT (presently BSNL). Later on flooded tubular positive plates batteries were used. As the telecom equipment can not withstand such a high voltage. Flooded batteries can not be transported in charged condition.1
Introduction The battery is an important constituent of the Telecom Network for sustaining the trouble free and uninterrupted service to its users. Maintenance of these batteries needs more efforts and is more labour oriented. recording SG of each cell and periodic discharge/charge cycles. Moreover. flooded flat-pasted type batteries were used in the Indian telecom network. it will be more difficult for the flooded batteries to meet the pollution norms.
thus saving the manpower and long connecting bus-bar or cables.MONITORING OF VRLA BATTERIES GUIDELINES
can be installed in the equipment room itself. more the sulphation gets hard and more it becomes difficult to remove it from cells/batteries. Effects : In the initial stages of the introduction of VRLA batteries. the sulphation of the plates starts setting in. 3 months or more. it was found that. TEC in February 1998. The Temperature in case of VRLA
. so that. This is termed as self discharge. The kinetics of these batteries are temperature dependent. the manufacturers were made to improve their battery design to ensure : • To minimise the self-discharge. All the above characteristics make VRLA batteries ideal stand by power source for Telecom applications. say. to make it direct to site item.1.
1. Self discharge of these cells/batteries is about 14 percent every four weeks. the cumulative self discharge over a period of 6 months. These cells/batteries get discharged of its own on its internal resistance and some localised action within the cells. The chemical reaction increases/decreases in geometric progression which the increases or decrease in temperature. Through this requisition the risk of hard sulphation was reduced a bit.1 But these batteries have their own problem and limitation.2
Temperature Effect : Batteries are very temperature sensitive. If these cells/batteries are allowed to remain in this state for a long period of time. which was one of the reason for under par performance of these batteries in the initial stages of introduction. at an average temperature of 35 degree Celsius is below 50% ( for AGM Batteries) or 25% ( for GEL Batteries) of its rated capacity. can be installed in any orientation. Some of the constraints are : Self Discharge : As these batteries are supplied in charged condition. for issuing necessary guidelines to the field units. 1. In year 2000 in the second issue of the GR. hence have a small size. which require timely and intelligent handling. To cut down the storage time. requested TC HQ. issued in August 1994. More the time it is allowed to remain in this state. This fact was clearly indicated in the first version of the GR. As these batteries are based on starved electrolyte principal. these battery were kept in storage for very long period of six months and even much higher. Plates of these batteries have a higher current density. Even than it is essential that the battery is commissioned with in the shortest possible time and a storage period of more than three months is avoided.1. Recommendation : It is essential that these cells/batteries are commissioned in the least possible time so that self discharge and subsequent sulphation layer is kept to minimum.
iii) The charging current to the battery may be restricted to defined limit ( 0. and gases/water will be vented out and permanently lost. which means dry out and thermal runaway in VRLA cells. If the cell temperature increased while holding the voltage constant. the proper temperature is essential for the optimization of battery life. will lead to an explosion and fire.30 for charge. the average temperature shall be maintained around the designed temperature at 35°C.e.1C recommended). The recombination of gases within a VRLA cell can only take place at a certain rate. High temperature also causes gassing. Charging voltage shall be such that it does not contribute to rise in temperature i. cell may be undercharged. If the rate is exceeded.30Volts. leading to the problems described under low voltage. High Temperature effect : The chemical reaction becomes faster and faster with rise in temperature above the design temperature (27 degree Celsius) and give rise to a chain reaction. Thermal runaway leads to a melting down of the jar and under worst. Internationally the batteries are design at 25 deg Celsius or 27 deg Celsius. gas pressure will built up beyond the safety valve level. the life is cut to half. The highest float voltage at which a cell still recombine all the gases driven off the plates is approximately 2.MONITORING OF VRLA BATTERIES GUIDELINES
Batteries is significant because of limited volume of electrolyte which restricts heat conduction. a higher float voltage is required to maintain full charge and if charger is not adjusted properly. a) Low Temperature effect : Battery capacity is diminished at low temperature. Also the charge acceptance decreases with the decrease in temperature.case scenario. In the light of this fact.e. iv) A provision shall be made so that the charger voltage shall be regulated as per battery temperature to slow down the battery kinetics. the cell would dry out and possibly go into thermal runaway.
. High temperature causes loss of life because every 10 deg Celsius rise in operating temperature.25V for float and 2.
Recommendation : i) Batteries temperature shall be maintained to such a value that it does effect the life and performance of the battery i. Therefore at low temperatures. 2. It may be ensured that Battery Temperature compensation unit in the power plant is fully functional & all the terminations are in proper place. The provision for battery temperature compensation has been made in the Power Plants.
1. Effect : if the cells are not properly matched. which puts pressure on the paste.25V as float and 2. premature failure of cell may take place. The highest capacity single cell based GEL technology is 3500AH. Do not resort to fast charging setting higher float/charge voltages.1
. However paralleling of cell for VRLA batteries based on GEL technology has not been recommended by TEC. This results in loss of contact of the
1.30V as charge. Float and Charge voltages have been recommended as 2. cells below 100AH are not permitted. Deeper the discharged.4
Charging Techniques : For this a special charging technique is required to ensure that charging does result in temperature rise.2.1C is recommended. For paralleling.MONITORING OF VRLA BATTERIES GUIDELINES
Though not mandatory. To achieve the higher capacity paralleling of cell become a Cell module is essential. voltage and
iii) Cell/Cell module matching for capacity. Recommendation : i) A constant voltage technique with battery path current limited to 0. During charge the paste of the +ve gets converter back into PbO2 The paste gets contracted. more is the increase in the volume of the paste of the positive plate and more is the pressure on the grid.
1. PbO2 of the +ve plate gets converted into PbSO4 there is a large increase in its volume. This expansion and contraction results in loosening of the active material in the grid. it is preferable that the battery may be installed in controlled environment for longer life and better performance. Recommendation : i) ii) Number of paralleling of cell is restricted to four.
1. Conductance has been made necessary. over a period of time.1.2
Failure of VRLA batteries : Most common reasons for failure of VRLA batteries are : Positive grid corrosion : Every time battery discharges.3
Paralleling of cells unavoidable : The highest capacity of single cell available for AGM batteries is 1500AH.1. because of higher internal resistance of these type of cells.
In case the sulphation is soft (not very thick). Deep Discharge. the same may be recovered by charging the cell along with the battery. This may happen due the excessive escape of gasses from the cell. 2. This may be achieved by cycling the cell inside the battery or removing the cell from battery bank and reconditioning. This is a recoverable damage unless it is hard enough to remove and can be recovered by careful and controlled charging of the cell. Fast rate of Discharging. 1. 3. In addition to ageing there are other factors which accelerate the process and lead to premature ageing. However. The medium type of sulphation can also be removed by prolonged charging. Some of them are : 1. This is a gradual process and under normal circumstances is a sign of ageing. the gasses escape through the safety valve to maintain the pressure within cells in prescribed limits and therefore. Fast rate of Charging. which shall only take place when the battery has lived its stipulated life. deeper the discharge faster the ageing.3 Dry out (loss electrolyte) : There is a misconception that these batteries are fully sealed and no escape of gasses take place.MONITORING OF VRLA BATTERIES GUIDELINES
active material with the +ve plate and increase in the cell resistance.2 Sulphation : Sulphation of the cells plates due to prolonged under charge. which may be complete or part depending on hardness of the sulphation. overcharge or prolonged storage may also increases the cell resistance. special treatment of charging etc. 1. which leaves the cell with little or no electrolyte. In both the above cases a few charge/discharge cycles are required for the optimum recovery.2. 4. at the factory by the manufacturer at his premises. In such a case cell is supposed to be damaged beyond repair. This may happen due to :
.2. most common mode of failure of the cell/battery is dry out. Some times sulphation becomes too hard to overcome. Larger number of charge/discharge cycles faster the ageing process. Corrosion is un-recoverable and indicates the end of cell life.
resulting in to cracks. It may be mentioned here that both of the above Abrupt and Low capacity failures can be detected. As the battery ages due to any reason it starts loosing its capacity. it fails to take the load. loose connection etc. the cells with high resistance are not deducted in time. The two main reasons in such cases are : a) Improper or Loose inter-cell connections : In case the inter-cell connectors are under rated will get excessively heated and may affect the sealing. internal
b) Some times the increase in resistance of the battery may not be an indication of the failure of cell or the battery because it may be due to rusted terminals. 1.
The indications for above failure are : a) The first indication for the failure is increase in the resistance of the cell or resistance of the battery. 1. If the battery capacity fall below the 80% of its original capacity. Abrupt failure will only occur.MONITORING OF VRLA BATTERIES GUIDELINES
b) Operation of the battery at a very high temperature c) Leakage through cracks in the container or sealing. Because. which can alarm well in advance about the failure tendency in a cell or the battery. therefore is very essential that it shall be checked periodically that neither the terminal is rusted or the terminal is loose(for this it shall be ensured that the torque of the terminal is as per manufacturers’ instructions. when the corroding will get very severe i.
. If the capacity of any cell/battery is approaching it requires immediate replacement. which in turn lead to escape of gasses and dry out.5 Low capacity Failure : This failure may mainly be attributed to ageing. if allowed to remain loose may cause premature failure of the cell/battery..2. fusing or terminals.4 Abrupt Failure : Due to lack of proper monitoring schedule. by observing a few indicators. well in advance ( unless the cells cracks or sealing gets open due to sustained high terminal temperature). b) Increase in the internal resistance of the cell/cells : This may be caused by sulphation or corroding of the plates. this. it is presumed to have lived its life. at the verge of breaking. because decaying of cell or battery is a gradual process and can be detected much in advance.2.e. Ageing is very slow process in initial stages of decay and gains speed only when it nears 80% of its rated value. when the battery is put on load. In such cases.
case scenario. The chemical reaction increases/decreases in geometric progression with the increases or decrease in temperature. but in India it has not been observed till date and moreover at present it is not considered failure mode. The battery room shall be employed with the natural air convection (ventilated room) and exhaust fan. gas pressure will built up beyond the safety valve level. Thermal runaway leads to a melting down of the jar and under worst. Thermal runaway is calliopes of the battery due to very very high temperature developed inside the battery. The Temperature in case of VRLA Batteries is significant because of limited volume of electrolyte which restricts heat conduction.MONITORING OF VRLA BATTERIES GUIDELINES
Thermal Runaway : Batteries are very temperature sensitive. the proper temperature is essential for the optimization of battery life.3
Factors leading to the premature failure and affecting the life & performance of the battery : Some of the common factors which affect the premature failure and affecting the life & performance of the battery are : a) Battery discharge b) Improper Charging c) No Temperature control
. The highest float voltage at which a cell still recombine all the gases driven off the plates is approximately 2. The user shall ensure that the ambient temperature of the battery room has been reduced by employing the natural air convection (ventilated room) with exhaust fan.
1. If the cell temperature increased while holding the voltage constant.30Volts. Temperature compensation of the battery. The user shall ensure that all the above features of SMPS Power Plants are fully functional and properly set. and gases/water will be vented out and permanently lost. If the rate is exceeded. In the light of this fact. Recommendation : i) The SMPS Power plants are fully compatible to prevent any excessive temperature in the battery by the features Battery path current limiting. High voltage cut-off and Precise voltage set in the Power Plant. The recombination of gases within a VRLA cell can only take place at a certain rate.2. will lead to an explosion and fire. In the initial stage of VRLA battery development of thermal runaway was considered one of the failure mode. the cell would dry out and possibly go into thermal runaway.
1.e. lesser the expected life of the battery. Recommendations : The battery shall not be allowed to discharge beyond 80% of its rated capacity. 1. Same battery when discharged to 50% of its rated capacity it may give about 1800 such cycles and will give only 1400 cycles if discharged to 80% of its capacity. The same battery if discharged to its full rated capacity may only give about 600 such cycles only.MONITORING OF VRLA BATTERIES GUIDELINES
d) Cell Matching e) Storage of VRLA Batteries f) Improper installation
g) Manufacturer Problems h) Operational/Maintenance issues.e.1.3.3.1. This will help to have a good idea about the health and remaining life of the battery. and compatible charger a telephone exchange battery.1 Battery Discharge : Deep discharge of the battery : It is a universal fact that deeper the battery is discharged lesser the life of the battery we get.1. moderate ambient temperature (10°C to 35°C). Each & every battery discharge shall be properly logged.1 1.2 Frequent discharge or Excessive cycles : As already explained under the heading Grid corrosion.3. on true float may give about 15 years of its service life. The battery application in Indian Telecom Network is neither of the two extreme categories. the cycling affects the life of the cell/battery.3 Discharging of Batteries at faster rate : The faster the rate of discharge of a battery lower is its expected life for example discharging battery at C/1 rate of discharge will give just half the number of DOD cycles than the battery which is discharged at C/8 or C/10 rate of discharge. Four year approximately. This can be understood by the fact that an exchange battery when discharged to 20% of its rated capacity. Recommendations : The battery shall not be allowed to discharge beyond 80% of its rated capacity. So more the deep discharge cycles/year.3. 1. The same battery in cyclic discharge application to 80% DOD (Depth of discharge) will give only 1400 cycles i.
. may give up to 3000 such cycles. Moreover it is not recommended to discharge the battery beyond 80% of its rated capacity as it affects the expected life of the battery severely. Charging not faster than C/10 rate. Under ideal conditions i.
01 to 2.2. 1. hence the power plant designed for flooded batteries are not suitable for AGM and GEL VRLA batteries. In case sufficient current is not allowed to flow through it the sulphation gets harder and harder. iii) Set the float & charge voltages as per battery manufacturer’s instructions. This will lead to loss of active material from the negative plate.5 to C/5) is an essential requirement. 1. charge rate also depends on temperature of the electrolyte.3. iv) At the time of installation/commissioning of the battery. sulphation may become hard and difficult to recoverable battery.. Temperature on the other hand also depends on the charging voltage. consequently it becomes difficult to break such sulphation.MONITORING OF VRLA BATTERIES GUIDELINES
Recommendations : i) The exchange/transmission & similar application batteries shall be so chosen that they are not allowed to discharge faster than C/6. ensure that the battery. is fully charged before putting on load. as in the case of UPS systems etc.
ii) Use the power plant which is compatible with VRLA batteries & has enough capacity to take care of load and battery at C/10 rate of charge.1 Under Charged Battery : Under. GR/BAT-02/02 MAR 2006 only be used in such cases.11 to 2.
. being starved electrolyte type are more sensitive to temperature. ii) Where faster discharge( C/0. In case the battery is kept in under. Therefore. Moreover the open circuit of AGM and GEL VRLA batteries is higher (2. The battery for high rate of discharge application No.07V).17V) than conventional flooded load acid batteries (2.charged condition for a long time it loses its rated capacity due to sulphation.charged.3. these batteries are required to be charged at precise voltage to prevent the overcharging or under charging of the battery. the battery may be planned with the lower expected life as per the rate of discharge. The charge rate is voltage dependent.charging leads to sulphate crystal formation on the plates. In case the battery is kept under charged for a very long duration. It becomes very essential that proper balance between three is achieved.2 Improper Charging : VRLA batteries. Recommendations : i) Ensure that battery is not allowed to remain under. It is clear that all the three parameters are interdependent. Follow manufacturer’s guidelines in this regard.
The recombination of gases within a VRLA cell can only take place at a certain rate. At 27 deg Celsius.25V/cell & 2. ii) Higher float/charge voltage Recommendations : i) Use the power plant which is compatible with VRLA batteries. vi) Set the battery path current in the power plant so that battery path current for each battery in the battery bank is restricted to 10% of the battery capacity. Change-over from float to charge & viceversa is automatic in the SMPS power plants as per TEC GR No GR/SMP-01/05 JAN 2005 with amendments if any.charging are : i) Higher battery temperature. The two main factors which may cause over.30Volts. v) Though not mandatory it is advisable to place the batteries in cooler environment for longer life and better performance.3 Temperature affect : Batteries are very temperature sensitive. The chemical reaction increases/decreases in geometric progression with the increases or decrease in temperature. and gases/water will be vented out and permanently lost. the highest float voltage at which a cell still recombine all the gases driven off the plates is approximately 2.3V/cell respectively. The kinetics are temperature dependent.2
Over.charging causes excessive gassing of hydrogen and oxygen. If the rate is exceeded. iii) Ensure that battery temperature compensation in the power plant is fully functional & all the terminations are in proper place. 1.Charging of Batteries : Over. gas pressure will built up beyond the safety valve level.3. The proper temperature will optimize battery life and is especially critical for VRLA Battery. Moreover excessive charging accelerates grid corrosion. This will lead to the frequent opening of the valve to release the internal pressure and consequent result in the long run is drying out. The charging of VRLA battery at too high rate is another factor which affects its performance & life severely. If the cell temperature increased while holding the voltage
ii) Float & Charge voltages at 27°C shall be set at 2. iv) Do not resort to fast charging by setting higher float/charge voltages. It will also increase the temperature of the cell.MONITORING OF VRLA BATTERIES GUIDELINES
1. because high uncontrolled temperature may lead to thermal runway.2.3. which is not desired for VRLA battery.
constant. iii) Though not mandatory it is advisable to place the batteries in cooler environment for longer life and better performance. the cells/modules in a battery and battery strings in parallel working require proper matching to prevent the higher current to be pumped in a cell. which means dry out and thermal runaway in VRLA cells. if the battery manufacturer desires. the cell in a cell module. a) Effect of Low Temperature : Battery capacity is diminished at low temperature. On the other hand the VRLA Cell capacity has its limitation. only after the prier concurrence of the concerned Power Plant supplier. As such the cell matching in case of VRLA batteries becomes more important. Therefore at low temperatures. leading to the problems described under low voltage.35V is fatal. will lead to an explosion and fire. cell may be undercharged. the life is cut to half. Till date the maximum capacity of AGM VRLA Cell in India is 1500AH.
ii) Do not resort to fast charging by setting higher float/charge voltages. at a rate higher than 2. 1. The battery internal resistance and impedance/conductance varies with capacity. More over conventional batteries require it charging at higher voltage of 2. However. Also the charge acceptance decreases with the decrease in temperature.3.4 Cell Mismatching : The conventional cell are available in any capacity up to 5000AH as such the paralleling of these cells to enhance the battery capacity is not required.33V/cell maximum under manual supervision. Due to this fact. age and even the manufacturing techniques and plate material. a higher float voltage is required to maintain full charge and if charger is not adjusted properly. Recommendation : i) Ensure that battery temperature compensation in the power plant is fully functional & all the terminations are in proper place.
. module or battery. High temperature causes loss of life because every 10° Celsius rise in operating temperature. b) Effect of High Temperature : The chemical reaction becomes faster and faster with rise in temperature above the design temperature ( 27° Celsius) and give rise to a chain reaction. High temperature also causes gassing. To achieve higher capacity battery the cells are connected in parallel. Thermal runaway leads to a melting down of the jar and under worstcase scenario. the battery can be charged up to 2. More over charging VRLA batteries. the cell would dry out and possibly go into thermal runaway. As such a capacity window of 100% to 120% was sufficient to take care of series cell matching in these type of batteries.7V/cell to prevent stratification.
At site only interconnection of cells is required to be done.site item & it shall be ensured that the battery is commissioned within 6 months of its dispatch. The VRLA batteries are formed in the factory. iii) In case of storage period of more than 6 months. voltage and capacity matching shall be done before putting them into use. If these batteries are allowed to remain idle for a very long time. The VRLA batteries are transported and stored in the fully form condition. iii) The cells of same rating & make shall be used to form a battery.3. If unavoidable.11 and 1. the following factors shall be checked so that it does not affect the life and performance of the battery seriously :
. proper impedance/conductance. respectively. ii) The battery shall be given freshening charge & ensured that full rated capacity has been recovered before putting it to load/use.
ii) The cells in a battery shall be connected in the order given by the manufacturer.6 Installation : At the time of installation itself. GR/BAT-02/02 MAR 2006.3. say more than six months these battery may get damaged beyond recovery due to sulphation.3. 1. This is because all the batteries including VRLA batteries lose their charge due to self discharge. hence these batteries are less time consuming as far as commissioning is concerned. whichever is applicable.11 of the GRs for VRLA batteries No. 1. Recommendations : i) VRLA batteries shall be considered a direct. the battery capacity shall be fully recovered before putting it to use. iv) Battery in the parallel string shall preferably be of same age.to. GR/BAT01/03 MAR 2004 with amendments if any or VRLA batteries for high rate of discharge (UPS) application No.MONITORING OF VRLA BATTERIES GUIDELINES
Recommendations : i) It shall be ensured that the cells in a cell modules & cell & cell modules in a battery comply the cell matching requirements of clause 5. It is therefore essential that these batteries are installed and commissioned in the shortest possible time after their dispatch from the factory.5 Storage of VRLA Batteries : The conventional batteries were formed at site and due to this fact a lot of time was required to install the battery.
it may lead to sulphation of the plates and may loose its capacity gradually.7 Manufacturing Defects : Common manufacturing defect encountered in the field are : i) Improper terminal rating.3. iii) Check loose inter. iii) Improper interconnection iv) Improper plate formation technique or its fusing. the over-discharge causes abnormal expansion of the active material in the plates.
ii) Cell matching (Voltage.3
.MONITORING OF VRLA BATTERIES GUIDELINES
Manufacturers Installation guidelines.8.8. iii) Over-discharge. Lead hydrate causes the plate surface to turn white and. ii) Keeping the battery continuously in undercharged condition. rendering the battery irreversibly damaged.3.cell connection or with improper torque. Capacity and Conductance).8 Operational Problems : The following conditions should be avoided : i) Keeping the battery in discharged or nearly discharged condition. seal or container.3.8. the electrolyte starts charging from an acid solution to almost pure water when the battery is fully discharged.1 Keeping the battery in discharged or nearly discharged condition : A discharged or near fully discharged cell will be damaged and possibility ruined if not charged within 24 to 48 hours.2
1. ii) Faulty seal design.cycling.3. because it is conductive. 1. As a battery discharges. iv) Check to detect damaged terminal. v) Do not put the battery to load without fully recovering its capacity. it forms a short circuit between the plates. which leads to permanent damage and also recharging
1. Keeping the battery continuously in undercharged condition : If the battery is kept continuously under charged due to any reason. 1. 1. Lead dissolves in water and some of the plate material mixes with water to form lead hydrate.3. Over-discharge : As explained earlier under the heading over.
Some of the traditional charging methods adopted for the recoupment of the battery capacity lost during discharge are : Constant Voltage Charging ( CVC) : This is the prevalent method used for charging of VRLA batteries.4
1. This causes the loosening of active material in the positive plate. Fast recoupment i. Erratic power supply conditions.9 Factors that affect the life and performance the battery in Indian Telecom Network : Indian Telecom Network problems for the maintenance of VRLA batteries are similar any other developing tropical country.3. In this method the charge voltage for the battery is fixed as per the manufacturers instructions. Some of the major problems which require solution are : 1.1 Erratic Power Supply conditions : This is the major challenge which requires to be handled.3. To prevent the battery form damage. After a discharge.4.3V/cell. Sulphation affects the life and capacity of the battery very severely.MONITORING OF VRLA BATTERIES GUIDELINES
problems. which in long term becomes difficult to remove. Due to this fact the batteries remain under charge and if there is no alternate source of power. that too not continuous) or not available at all. Undercharge condition battery gets sulphated. fast rate of charging : It may be mentioned here that whatsoever method we may adopt 90% of the lost capacity of battery will be recovered in even time. in the initial state of charging the battery may draw very heavy current.3. Comparatively high working temperature. the undercharge condition gets worse and worse. 1.1
. it is very essential that this current shall be restricted to some limit (normally
1. Longer the period the battery remains undercharge the sulphation gets harder and harder. It is either available for a very short time (4 to 8 hours a day. 1. Options for recoupment of battery capacity and their impacts : Various options available for the recoupment of battery capacity and their impacts are as given in ensuing paras. In most of the parts of the country either commercial power supply is scarce. The consequential effect of under charge condition of the battery have already been highlighted earlier.3.9. 2. This will lead to increase in resistance and failure of the cell/battery.9. as for as telecom network is concerned.3.2 Comparatively High working Temperature : This has been already explain in clause 1.e. leading to loss of contact with the grid. Normally it is 2. 1.
ii) As in this method. this limits may be based on the following considerations : i) The manufacturer’s recommendation. 1. Moreover the current going into the battery is as per battery requirements.MONITORING OF VRLA BATTERIES GUIDELINES
0. Therefore this method minimise the risk of overcharge. This is the power plant’s capacity in excess of the maximum equipment load. iii) Time during which the recoupment is battery lost capacity is required.
. Otherwise.4.3
Why constant voltage charging is preferred : i) Precise voltage regulation is possible.4.1C recommended). charge efficiency of the battery is also improved. the charging current gets reduced.2 Relationship between charge voltage and recharge time :
1. ii) The charger capacity (the maximum current it can spare for the battery) of the charger. as battery lost charge is recouped.
This is called auto float charge operation. Float voltage is set as per battery manufacturer recommendation (normally 2. SMPS power plants automatically upgrades its voltage to a higher set limit This charge voltage is set as per : a) Manufacturer’s recommendation (safe voltage for the battery). Charging Current limit.5C and 1. it may be mentioned here that the minimum recharge period for 100% recoupment is minimum 48 hours.
.25V/cell recommended). desired state of charge and temperature.2C. 0. Present day SMPS power plants have a provision for automatic dual voltage setting.1C. However. 2. Charging voltage. To determine the anticipated recharge time at 27°C the following equation can be used : T RX% Ic Where : = AHR X ‘Kx’”
TRX% :: Recharge time in hours to X% state of charge (SOC) AHR : Ampere hours removed during previous discharge : Maximum available charging current in Ic ampere’s ‘Kx’ ”: Constant based on approximate maximum charging Current (0. b) Duration for recoupment : Two major factors that can accelerate the recoupment are : 1.MONITORING OF VRLA BATTERIES GUIDELINES
iii) Charge voltage and limiting current can be varied as per the battery charge duration requirements and available charge. Normally when the battery is fully charged the charger voltage remains in float mode (low voltage).0C) available Based on above formula the typical graphs are generated as follows. recharge voltage maximum charging current. The different combinations that can be adopted for fast charging are : Recharge time is a function of rate and depth of discharge. 0. When the charge is available after every discharge.
1C) Vs Various Depths of discharge
80% 90% 95% 100% DOD SOC SOC SOC SOC 10%
100% 100% SOC SOC
0 0 1 2 3 4.3 12 15
95% SOC 1.25V/cell and Current limited to 0.5 3 4 5.2C) Vs Various Depths of discharge
80% DOD SOC
100% SOC 100% SOC
90% SOC 0 1.5 18 24 31.1 9 12
Hours recharge
30 95% SOC
90% SOC
20 90% SOC
80% SOC
0 0 1.5 8.25 V/cell and Current limited to 0.5
Graph showing Recharge Time (Voltage 2.5 9.5 7.4.1C) Vs Various Depths of discharge
80% 90% 95% 100% DOD SOC SOC SOC SOC
0 0 2 3 5 8 10 12 16 20
0 2 4 5 8 10 12 16 20 24
2 3 6 8 12 16 20 24 30 36
3 5 8 12 16 24 32 42 55 72
90% 90% SOC SOC
20 10 0 10% 20% 30% 40% 50% 60% 70% 80% 90%
1.5 13 16
1 2 3 4.5 9 12 16 20 24
2 3 5 8 11 16 22 30 40 50
30 95% SOC 20 90% SOC 10 80% SOC 0 10% 20% 30% 40% 50% 60% 70% 80% 90% 100%
90% SOC 80% SOC 95% SOC
.3 2.5 2.8 5.5 11 14.5 18 22
100% SOC 2.9 7.1 6 8.8 6 9 12.5 10.5 6 8 10
0 1 2 3 5 6.3V/cell limited to 0.5 41.MONITORING OF VRLA BATTERIES GUIDELINES
Graph showing Recharge Time (Voltage 2.3 3.5 6.5 4.6
Graph showing Recharge Time ( Voltage 2.3 3.4.4.
5 2.5 30 37.8 6 8.35V/cell and Current limited to 0.5 50%
0 10% 20% 30% 40% 50% 60% 70% 80% 90% 100% Depth of discharge
1.25 3.5 4.75
15 90% SOC 90% SOC 10
50% 2.2C) Vs Various Depths of discharge
90% 95% 100% SOC SOC SOC 0 0.5 9
30% 0. which is not desirable. the charging time is reduced.4. Excessive gassing may lead to early dry-out.25
1.5 1 2 3 4 6 7 8 9
0. If at all required it shall only be used temperature compensation
.5 22.5 3.5 6 7.9 6.3 12 16. b) Charging at 2.4 4. It has its own limitations and side effects : a) Charging voltage 2.5 2.75 4.35V/cell or higher : In case of AGM VRLA batteries 2.75 1.25 3. it may result in rise in the cell temperature.5 18 1. More over it will result in increase in the battery temperature.5 1 2 3 4 5 7 8 10 12
1 2 3 5 7 9 12 18 20 24
20 Hours recharge
30% 0.8 9 11.4 8.5 14. which depends on the battery design.5 2. which is not desirable.75 1.3V and Charging current 0.35V is considered as a gassing voltage.2C) Vs Various Depths of discharge
Graph showing Recharge Time ( Voltage 2.3V/cell and limited to 0.4.9 6.2C : As the cells and battery has some limit to charge acceptance.9
Analysis of Graphs and Tables : On the analysis of the graphs and tables for various charging voltages and battery path current limits.25 3.4.5
10% 20% 40% 60% 70% 80% 90% 100%
0 0 1. If higher current for long duration is permitted.MONITORING OF VRLA BATTERIES GUIDELINES
1. it may be observed that by increasing the charging voltage or battery path current or both.1 10 12 0.8
Graph showing Recharge Time ( Voltage 2.
Moreover this will require the additional FR-FC modules for the charging of the battery.4.5 1. we will require 8 FR-FC modules if battery path current is limited to 0.27V and 2. e) Use only power plant compatible with VRLA batteries. Also ensure that these limits are not disturbed. In the initial stages of its inception these batteries were called Maintenance Free Batteries. c) It shall be ensured that the temperature compensation in power plant is fully functional and connected to the battery.33V respectively. if the battery manufacturer recommends.10 Battery Charging Solution for recoupment solution for fast recoupment. Note : These limits can be set.1
Monitoring of VRLA Batteries : No foolproof indicators/tools for knowing and predicting the health and life of the battery has been evolved/devised. 1. This will also help in overcoming polarisation of the +ve plate. For example if at present 4 modules are required for the charging of the battery. b) Set the battery path current limit as per the power plant capacity. because it may case sulphation. d) Battery shall not be allowed to remain under charge for longer period of times. But in no case it shall be higher than 0. under manual supervision only after the prier concurrence of the concerned Power Plant supplier.e.MONITORING OF VRLA BATTERIES GUIDELINES
circuitry fully connected and functional. i.2C.
1.5. which has led to failures of these batteries. no proper attention has been given to these batteries. The commonly used parameters to keep the tab on the health and life of the Flooded type batteries such as observing the level of electrolyte
. Idea of mobile DG set for a group of stations may be explored to fully charge the battery periodically.2C. This terminology gave the impression to the users that these batteries are to be “ installed and forgotten. f) The battery shall be sized properly so that the autonomy requirements are met with 80% of its rated capacity (50% in the cold regions). may be : : The most ideal
a) Increase the Float charge voltages up to 2. ” Due to this misconception. in case the electric supply conditions is such that the battery can not be recouped by AC mains. available power plant rating minus the equipment load.
combining some of them.5.2.2. Some of the methods/techniques used for the prediction of the state of health & expected residual capacity of the battery are : a) Periodic physical inspection of each cell of the battery for cracks & leakage etc. crack or leakage.1 Float current in fully charged battery. expected life and expected residual life of the battery was being felt because it was essential for the service provider to keep himself informed about the state of health of battery and warn him well in advance about the impending failure of the battery for the provision of uninterrupted telecom services to its users. capable of foolproof prediction about the impending failure of the battery has been evolved/devised. which could give some idea about the state of charge.2 A large number of techniques/methods have been explored and tried by various agencies in the field.5. f) 1. Till date.5. Since the VRLA batteries were introduced in the Department. d) Measurement & recording of cell temperature periodically. On the other hand.MONITORING OF VRLA BATTERIES GUIDELINES
measured of SG (Specific Gravity) can not be applied to VRLA batteries as they are sealed batteries using starved electrolyte technology. It shall also be ensured that sealing has not developed any type of deformity. the need for some device or method or technique. not a single method/test instrument. the state of health & expected residual life of the battery can be predicted more precisely & reliably.
. These measurements shall be taken OFFline as detailed in clause 1. c) Measurement of a mark deviation (>30%) in the Impedance or conductance of the cell as compared to the one recorded at the time of commissioning.
Periodic Physical inspection : Each cell in the battery string shall be inspected periodically for any damage. 1.3. Recommendation : Physical inspection may preferably be carried out every month and it shall be ensured that the inspection is carried out at least once in every two months. b) Discharge of battery for a short duration say 30 minutes to 1 hour and recording the voltages of each cell in the string. e) Float Voltage of cells & its comparison with the mid point voltage. An early detection may help in necessary remedial action to prevent failure of the cell/battery.
Every partial test discharge shall be properly recorded for future reference and comparison.
.) of the battery is discharged. In these cases analog meters become more unreliable because of noise induced by Telecom equipment & power plant. the battery is put to a test discharge by shutting down the power plant for short duration of 30 minutes. so that 20% (approx. Any cell showing drift in voltage.5. Different cells from different manufacturers & of different lots from the same manufacturers will have different Impedance/conductance.MONITORING OF VRLA BATTERIES GUIDELINES
1. Recommended Meter : Digital Volt meter shall be capable to read three place decimal with accuracy 1 mV.2. one hour or a duration as decided by the in-charge of the unit.5. It is also true that there is little data available on the long term trends of cell impedance/conductance.3
Conductance Measurement : Though a large number of test instruments are available for measurement of impedance & conductance but most of them are with poor reliability & accuracy. In case the battery is frequently discharged due to frequent AC mains interruptions. The voltage of each cell is recorded periodically during this test.2. More over these measurements are required to be carried in OFF Line ( when the charger is ‘OFF” and battery is on float). as compared to the voltages of other cells in the battery. By comparing this discharge voltages with the initial voltages we may have some idea about the loss of capacity of the cell and battery. The test discharge tables supplied by the manufacturer with the battery shall be kept at an easily accessible place as this table will be used as a reference. In this test. in excess of 5%. This test may be conducted on fully charged battery if it has not been put to load for some time. the observation can be recorded during such failures.2
Battery partial discharge test : This test is the most simple and un-expansive method to detect any sign of impending failure (not the expected residual life) of a cell in a string.
1. it shall be put to further scrutiny.
The gassing may onset the thermal runaway.5A. In the light of this fact it is essential to effectively monitor and control the temperature of the cell/battery. In the range 30% to 40%. But this has the following limitations : i) It monitors the temperature of the pilot cell. it shall be put to further investigation. it is very critical & difficult to predict the state of cell/battery because there is uncertainty of 5% in the measurement and also the reference impedance/conductance is also known to be within 5%. It is also true that faster the reaction higher is the active material shedding. The SMPS power plants as per GR No. There are a large number of meters available in the market with or without computer interface. It is also an important factor that the cell temperature and battery deterioration is not a linear but an Arrhenius relation ( every 10 degree rise in temperature double the chemical reaction).MONITORING OF VRLA BATTERIES GUIDELINES
Normally change in Impedance/conductance change less than 30% indicates the health state of cell/battery & more than 40%. ii) It simply slows down the chemical reaction by pulling down the charger voltage.5. The value impedance/conductance of each cell given in impedance/ conductance table provided by the manufacturers shall be verified at the time of commissioning and shall be taken as the reference. The readings may taken at the time of partial test discharge and scrutinised for deviations.
.4 Temperature of the cell/battery & life of the battery Temperature at which the battery works is an other important factor which affects the life of the battery seriously. 1. without creating an alarm. GR/SMP-01/05 JAN 2005 with amendments if any has taken care of the battery to some extent by slowing down the chemical reaction by reducing the charger voltage. the imminent failure of the battery/cell. Higher the temperature. The chemical reaction in the cell depends mainly on two factor the charging voltage and its temperature. faster is the reaction in the cell. In case deviations in any of the cell are observed outside the specified limits of 30%. Recommended Meter: Digital Impedance/Conductance meter with online accuracy 2% and resolution of 3 place of decimal. gassing and grid corrosion.2. Its power drain from the cell/battery during test shall not be more than 0.
1. Though the power plants as per TEC GR No. Temperature sensors with computer interface are available for the purpose.1° C. Though SMPS power plant as per TEC GR No. In this method monitor will create an alarm when there is a sufficient imbalance in the two half string voltage.1 1.MONITORING OF VRLA BATTERIES GUIDELINES
It is important to measure the individual cells temperature periodically and keep a record for study and analysis for prediction of the residual life of the battery. GR/SMP-01/05 JAN 2005 with amendments if any provide for temperature compensation of the battery.5.2.2.25V/cell for float voltage and 2. The float voltage shall be so set the corresponding voltage at 27 degree Centigrade shall be 2.5. Therefore it is essential to ensure that the parallel strings are properly matched for conductance and resistance.1. In this technique the voltage of each cell is measured and deviation in any of the cell can be detected quickly and easily and remedial action required can be taken.1° C and of accuracy of 0.2.5. the float current in each string will depend on the internal resistance of the string. This method has its own limitations because as the system voltage increases the midpoint monitoring loses its resolution and as such also loses its ability to discern a deviant cell.5.3V/cell for charge voltage taking the adjustment factor @ 3mV/cell/degree centigrade.1. Recommended Voltmeter : Digital Voltmeter shall be capable three place decimal with accuracy 1 mV. Recommended Meter : Thermometers/temperature sensor/probes shall be capable of reading in steps of 0. Moreover in case floated parallel strings. 1.5. 1.5.5.1 Float voltage Monitoring : Mid-point Voltage Measurement : Some battery monitors measure the midpoint voltage of each battery string. to read
. This is very simple approach to detect voltage deviations within string.5 Float Voltage : Float voltage is another important parameter on which the life & performance of the battery depends.2 Individual cell Monitoring : To achieve the optimum benefit of voltage monitoring it is essential that the voltage monitoring is done at cell level.2. but the initial setting of the battery float voltage is very essential. GR/SMP-01/05 JAN 2005 with amendments if any do have the provision for cell voltage monitoring but this facility has been incorporated recently in the power plants of some of the International manufacturers & may be incorporated.
Current Measurements : Currents for all the three states charge/discharge/float. of battery are important factors affecting and predicting the life and state of health of a battery or a battery in a parallel string.2. as per the given in the respective clauses of this document. In the light of this fact it is important that the batteries in a parallel string draw a current within a specified window/tolerance. for the parameters.
END OF THE PART 1
. Proper attention shall be given to the requirements while selecting such instruments. Recommended Meter : Digital meter shall be capable to read three place decimal with accuracy 1 mA. A large number of current measuring devices are available. when it is on float. It is also the opinion that a fully charged battery shall not draw more than 400mA at 27 degree centigrade. any mark deviation from this value need investigation. As the current being drawn by a battery or a battery in the parallel string will depend on the internal resistance and impedance/ conductance of a battery.6
Monitoring Schedule : The following Monitoring schedule for VRLA batteries is recommended by TEC :
RECOMMENDNED MONITORING SCHEDULE FOR VRLA BATTERIES ______________________|________________________ | | | Daily Monthly Quarterly | | | Temperature & Voltage Voltage of each cell Conductance of each cell during partial measurements in all the strings test discharge | Float Current Measurements | Physical Inspection
Note: The Batteries can be monitored.
1.MONITORING OF VRLA BATTERIES GUIDELINES
1.5. The battery with lower internal resistance will draw more current and as such faster chemical reaction.
04/02 MAR 2007
. GL/BAT.PART 2
(PLANNING OF VRLA BATTERIES)
GL No.
Small Rural exchanges. While choosing the battery it shall be ensured that the battery selected is suitable for specific application for which it is being procured. High rate of discharge systems : These type of batteries can handle higher rate of discharge which can be C/0.1. It is. Microwave repeater stations etc.2
2. where the battery back-up requirements are 6 hours or higher. Back-up time : The battery bank shall be capable of meeting the load requirements of equipment for specified number of hours. presently its number is GR/BAT-02/02 MAR 2006 with amendments if any.1.1
2.1. 12 or 24 hours for Large Switching Systems. small & large Transmissions stations respectively. This battery back-up is normally site specific. For SPV Power Systems it is 3 days to 7 days. For SPV power application the batteries are charged at a rate slower than C/10 rate to economise SPV power system.1. In these type of systems the batteries are discharged at C/6 rate or slower. These factors are : Discharge Application : From the application point of view the batteries may be classified mainly in the two categories : Slow rate of discharge systems : Switching systems large and small.MONITORING OF VRLA BATTERIES GUIDELINES
2. The normal practice for battery backup in the Indian Telecom Networks is 6. These type of batteries shall be in compliance of the GR for VRLA batteries and Tubular VRLA batteries based on GEL technology. Microwave repeater stations.1
Planning of VRLA Batteries Battery bank as per Load & Back-up requirements : The battery provides the necessary back-up for the uninterrupted power to the network. There are some of the primary factors which shall be taken in to account while choosing the capacity of the battery bank. While calculating the battery capacity for a given load & back-up time the following factor are to be taken into consideration : * The battery shall not be allowed to discharge beyond 80% of its rated capacity because it affects its life severely. These type of batteries shall be in compliance of the GR for VRLA batteries for high rate of discharge(UPS) applications. Transmission systems.1.1. GR/BAT-01/03 MAR 2004 and GR/BAT-03/01 MAR 2006 with the amendments if any. presently it is as per GR Nos.1.2
. Small Switching systems.5 to C/5 rate depending on the backup requirements of the system to be powered normally these type of batteries are used for UPS systems and other similar high discharge applications. essential to ensure that the capacity battery chosen is capable of providing the necessary back-up for which it is chosen. depending on the commercial mains supply conditions of the site. considering present and future backup requirements. therefore.1.
GR/BAT-01/03 MAR 2004 and GR/BAT-03/01 MAR 2006 with Amendments if any :
2. For example for four hour back-up the required battery capacity shall be load*4/(80/100) = load*1.125C 0.1.0 91.0 150.167C 0.75V 1.75V 0. 2. The VRLA batteries for slow discharge application (Discharge rate C/6 to C/120) GRs No.05C 0.125C 0. Hence battery will be discharged at C/5 rate instead of C/4 rate of discharge.5V
.1. * As the battery capacity is higher for the required rate of discharge because of the above reason.014C 0.0 (SPV Applicatio n only) 188 250 314 456 600-720 1440 5616 10800 1.0 100-120 120.0 150.3 Effective Battery Capacity : The effective battery capacity for a given rate of discharge shall be as per the tables 1 & 2 as given below depending on the type of battery selected.1
Rate of Discharge Cell Mono-Block
C/3 C/4 C/5 C/6 C/8 C/10 C/20 C/72 C/120
Discharge Capacity Discharge End cell Discharge Capacity Discharge End cell expressed time (min) voltage Current expressed time (min) voltage Current as % of as % of Minutes Minutes C/10 C/10 Discharge Discharge rate rate 0.2C 0.3.0 130.0083C 81.5V 10.3 87.44V 0. Same shall be true of other back-up requirements.333C 75.1C 0.25*4 = 5*load & not 4* load.25C 0.75V 1.0 100-120 120.75V 1.44V 10.333C 71.5V 10.75V 1.74V 1.1C 0.3 95.75V 1. for a given back-up shall be 25% higher than the actual back-up load.0 135 10.5V 10.014C 0. the effective rate of discharge for these batteries will be higher.5V 10.05C 0.0 85.2C 0.0 130. which will be good for the health and performance of the battery.0 (SPV Application only) 195 255 328 456 600-720 1440 5616 10800 10.5V 10.74V 0.75V 1.7 129 1.0083C 78.0 95.MONITORING OF VRLA BATTERIES GUIDELINES
* As the battery is not allowed to discharge beyond 80% of its rated capacity.5V 10. its capacity.2 83.25C 0.167C 0.
As per the table-1 given above.120 13.1.33 times its rated capacity to the end cell voltage of 1. less than C/20.1.33*C 0.25*C 0. In case the discharge current is equal to 0.75V 1. Faster the rate of discharge lower the capacity the battery will deliver.3.2V 10. GR/BAT-02/02 MAR 2006 :
Capacity Capacity expressed Discharge End expressed Discharge Discharge End cell Discharge as % of C/5 time (min) monoas % of C/5 time (min) voltage Current Current Discharge Minutes block Discharge Minutes rate voltage rate 2*C 1*C 0.120 15 39 102 164 231 300.360 1. when the battery is discharged at a current equal to 0.70V 1. For this purpose the proposed battery capacity is essential for battery path current limit setting. Charging of battery at rates faster than C/10 is not recommended : As the faster rate of charging is not recommended for VRLA batteries.5*C 0.5% with every one degree decrease in temperature.1.MONITORING OF VRLA BATTERIES GUIDELINES
2.70V 1.5*C 0.70V 1. GR/BAT-02/02 MAR 2006 are designed at C/5 rate of discharge and will give rated capacity only when it is discharged at a discharge current equal to 0. At all other discharge rates faster than the 10 hours or 5 hour rate as the case may be the battery will deliver less than its rated capacity.25*C 0.5V
C/0.4
The temperature at which the battery is to work : At temperature lower than 27° Celsius the capacity of the battery is reduced by 0.3% of its rated capacity and last for about 250 minutes instead of 300 minutes and so on.2
The VRLA batteries for high rate of discharge (UPS) application (Discharge rate C/0.3
The battery gives rated capacity only at the discharge rate for which it is designed.1*C) rate of discharge.
2. will be only 71.3.5V 10.33*C 0.5 to C/5) GR No.2*C. For example VRLA batteries for Telecom applications as per GRs No.2 time its rated capacity the battery will be 83.5
.1.7% of the rated capacity and last for 129 minutes instead of 180 minutes as anticipated.5 36 97 155 228 300 .2C 50 65 85 91 96 100.
2.2V 10. The relation between rate of discharge and expected capacity is as given in tables 1& 2 above.74V/cell.74V 1. GR/BAT-01/03 MAR 2004 and GR/BAT-03/01 MAR 2006 with amendments if any are designed at C/10 (0.360 10. it is essential that the power plant shall be programmed to ensure that current allowed to battery is restricted to 10% of its rated capacity.2V 10.44V 10. The VRLA batteries as per GR No.2C 45 60 81 86 95 100 .5 C/1 C/2 C/3 C/4 C/5
2.75V 2*C 1*C 0. This factor is of relevance at places where the ambient temperature goes very low (below 5 degree Celsius) and the rate of discharge is also low.
Note : The above mentioned sample calculation for battery-bank requirement can be selected as per nearer available capacity of batteries used in telecom network.As the battery is for slow discharge application.8)/0.873 = 6013. . Say : 700A : 6 hours : 80% : Planes of India
b) back-up required c) Permissible DOD d) Place where the battery is to work Battery Capacity Calculations :
.4 AH 700*(6/0. the battery shall be in compliance of the GRs No.0.7 AH say 6000 AH
400 A is the present rated load 700 A is the ultimate load 6 is the required back up time 0.
The battery-bank can be formed by selecting available batteries. considering all the above factors can be calculated as given below : At present : Ultimate : Where : 400*(6/0.8 is the capacity up to which battery is permitted to discharge . The required capacity of the battery.873 is the expected effective battery capacity at C/6 rate of discharge. The required capacity of the
. GR/BAT-01/03 MAR 2004 for VRLA batteries and GR/BAT-03/01 MAR 2006 for Tubular VRLA Batteries based on GEL technology with amendments if any.3.MONITORING OF VRLA BATTERIES GUIDELINES
2.8)/0.The Battery is expected to deliver the effective capacity of 87. The solution in this case is : two 2000AH batteries for the present load and additional 2000AH battery can be added at the later stage subjected to compliance of clause 1.1
Sample Calculations for battery bank : Sample Calculation 1 : Switching System : (Slow Discharge Application (Battery back-up 6 hours & higher)) Data Required : a) Load Present Ultimate : 400A ….873 = 3436.2 2.4 of part 1.3% of C/6 rate at discharge rate of C/10 as indicated in the given table -1 on page 25.2.
The solution in this case is : one 80AH battery for the present load and additional 80 AH battery can be added at the later stage .5 to 5 hours) Data Required : a) Load Present Ultimate : 50A ….8)/0.5/0. No.5 hours : 80% : Planes of India
b) Back-up required c) Permissible DOD d) Place where the battery is to work
Battery Capacity Calculations :
.Battery is expected to deliver the effective capacity 45% at C/0.MONITORING OF VRLA BATTERIES GUIDELINES
battery bank can be doubled in the tender by planning cell of service provider. the battery shall be in compliance of the GR for VRLA batteries for high rate of discharge (UPS) application. Say : 80A : 0.5 is the required back up time 0.5 rate of discharge.2 Sample Calculation 2 : Computer Terminal : (High discharge application (Battery back-up 0. The required capacity of the battery.As the battery is for high discharge application.2.45 = 111.8)/0.45 = 69.8 is the capacity up to which battery is permitted to discharge 0. depending up on the field conditions. 50*(0.44AH 80*(0.45 is the expected effective battery capacity at C/0.5/0.11AH
The battery-bank can be formed by selecting available batteries.
. considering all the above factors can be calculated as given below : At present : Ultimate : Where : 50A is the present rated load 80A is the ultimate load 0.5 rate of discharge of C/5 as indicated in the given table . 2. . GR/BAT-02/02 MAR 2006 with amendments if any.2 on page 26.
for recycling. 311 issued at New Delhi May 16. only to those units registered with the Ministry of Environment & Forests as recyclers possessing environmentally sound management facilities for reprocessing the same.2
2.envfor.
2.MONITORING OF VRLA BATTERIES GUIDELINES
2.nic.3.3 2.3. The list of approved recyclers of used/old batteries is available on the Ministry of Environment & Forests website (URL. 2001” The batteries shall be sold.3.www.in).3
END OF THE PART 2
Disposal of unserviceable Batteries The unserviceable batteries shall be disposed in accordance with Gazette Notification issued by Ministry of Environment & Forests “ Extraordinary Part-II-Section-3-Sub-section(ii) No.
Sometimes indicated when a battery is first placed in service or returned to service after prolonged storage. Capacity Retention : The fraction of the full capacity available from a battery under specified conditions of discharge after it has been stored for a period of time. Capacity : The total number of ampere-hours or watt hours that can be withdrawn from a fully charged cell. mono-block or battery under specified conditions or discharge. Closed Circuit Voltage (CCV) : The difference in potential between the terminals of a cell/mono-block or battery when it is discharging. that a cell/mono-block/battery can be stored in the charged condition before its capacity falls below a specified level. mono-block or battery at defined discharge rate and other specified discharge rates or operating conditions. Ampere-hour Efficiency : The percentage ratio of the output of the secondary cell or mono-block or battery. Ambient Temperature : The average temperature of the surroundings. to the input required to restore the initial state of charge. Conditioning : Cycle charging and discharging of a battery to ensure that it is fully formed & fully charged. Ageing : Permanent loss of capacity due to either repeated use or the passage of time. measured in ampere-hours. Available Capacity : The total capacity. It is affected by cell/mono-block temperature.MONITORING OF VRLA BATTERIES GUIDELINES
Terminology Absorption : The taking up or retention of one material or medium by another chemical or molecular action. Ampere-Hour (AH) Rating : The rating assigned to the cell/mono-block shall be the capacity expressed in ampere-hours (after correction at 27° Celsius) and stated by manufacturer to be obtainable when the cell/mono-block is discharged at 5 hour rate (C/5) to a final end voltage of 1. charge rates and state of charge.75V/cell or 11. by
Activated Stand Life : The period of time.
. Charge Acceptance : Willingness of a battery or cell or mono-block to accept charge. AH or WH. under specified conditions. Constant Current Charging : A method of charging the battery using a current having little variation. that will be obtained from a cell. at a specified temperature. Capacity Fade : Gradual loss of capacity of a secondary battery with cycling.5V/mono-block. Activation : The process of making a reserve cell/mono-block/battery function.
long-term constant-voltage charging. Continuous Test : A test in which a cell/mono-block or battery is discharged to a prescribed end-point voltage without interruption. Also used on a weight basis (WH/Kg).
. Cut-off Voltage : The cell/mono-block or battery voltage at which the discharge is terminated. Also called constant potential charge. End Voltage : The prescribed voltage at which the discharge (or charge. Cycle Life : The number of cycles under specified conditions which are available from a secondary battery before it fails to meet specified criteria of performance. and allowing variations in the current. usually within an hour. Energy Density : The ratio of the energy available from a cell/mono-block or battery to its volume (WH/V). Gas Recombination : Method of suppressing hydrogen generation by recombining it with oxygen on the negative electrode. if end-ofcharge voltage) of a cell/mono-block or battery may be considered complete (also cut off voltage). Depth of Discharge (DOD) : The ratio of the quantity of electricity (usually in ampere-hours) removed from a cell or battery on discharge to its rated capacity. Float Charge : A method of maintaining a cell/mono-block or battery in a charged condition by continuous. Cycle : The discharge and subsequent or preceding charge of a secondary battery such that it is restored to its original conditions. at a level sufficient to balance self-discharge. It is also called end voltage. Efficiency : The ratio of the output of a secondary cell or battery to the input required to restore it to the initial state of charge under specified conditions. Deep Discharge : Withdrawal of at least 80% of the rated capacity of a cell. Electrolyte : The medium which provides the ion transport mechanism between the positive and negative electrodes of a cell/mono-block. Current Density : The current per unit active area of the surface of an electrode. as the cell approaches full charge. mono-block or battery.MONITORING OF VRLA BATTERIES GUIDELINES
Constant Voltage Charging : A method of charging the battery by applying a fixed voltage. Also referred to as Back EMF. Counter Electromotive Force : A voltage opposing the applied voltage. Fast Charge : A rate of charging which returns full capacity to a rechargeable battery.
Load : The term used to indicate the current drain. using the same process and material. of a cell/mono-block or battery which will deliver the specified hours of service to a given end voltage. Maintenance-Free Battery : A secondary battery which does not require periodic "topping up" to maintain electrolyte volume. Lot : All batteries of the same type. in amperes. Over voltage :The potential difference between the equilibrium potential of an electrode and that of the electrode under an imposed polarisation current. In other words. offered for inspection at a time shall constitute a lot. Internal Resistance : The opposition or resistance to the flow of an electric current within a cell or battery. manufactured by the same factory during the same period. operated in successive cycles to the same. n is the number of cells or batteries connected in parallel & Cu is capacity of the each cell or battery. design and rating. Parallel connections increase the capacity of the resultant battery as follows : Cp = n X Cu . Life : For rechargeable batteries. the duration of satisfactory performance. Parallel : Term used to describe the interconnection of cells or batteries in which all of the like terminals are connected together. but less than a full.
. Oxygen Recombination : The process by which oxygen generated at the +ve plate during charge is reacted at the -ve plate. continued charging after 100% state of charge is achieved. Overcharge : The forcing of current through a cell/mono-block after all the active material has been converted to the charged state. Where Cp is the resultant capacity. Over discharge : Discharge past the point where the full capacity of the cell/mono-block has been obtained. Hourly Rate : A discharge rate. Open-Circuit Voltage (OCV) : The potential or voltage of a cell/mono-block or battery when it is at the surface of the electrode. measured in years float life) or in the number of charge/discharge cycles (cycle life).MONITORING OF VRLA BATTERIES GUIDELINES
Half-Cell : An electrode (either the anode or cathode) immersed in a suitable electrolyte. depth of discharge experiences a depression of its discharge voltage and temporarily loses the rest of its capacity at normal voltage levels. Memory Effect : A phenomenon in which a cell. It is the sum of the ionic and electronic resistances of the cell/mono-block components.
Rated Capacity : The number of ampere-hours a cell/mono-block or battery can deliver under specific conditions (rate of discharge. temperature): usually the manufacturer's rating. & so on. electronically non-conductive. spacer or material which prevents electronic contact between electrodes of opposite polarity in the same cell. State-of-Charge (SOC) : The available capacity in a cell/mono-block or battery expressed as a percentage of rated capacity. Specific Gravity : The specific gravity of a solution is the ratio of the weight of the solution to the weight of an equal volume of water at a specified temperature. Self-Discharge : The loss of useful capacity of a cell/mono-block or battery due to internal chemical action (local action). Series : The interconnection of cells/mono-blocks or batteries in such a manner that the positive terminal of the first is connected to the negative terminal of the second. Recombination : A term used in a sealed cell construction for the process whereby internal pressure is relieved by reaction of oxygen with the negative active material. or battery before a
Shelf Life : The duration of storage under specified conditions at the end of which a cell/mono-block or battery still retains the ability to give the specified performance. end voltage. Starved Electrolyte Cell : A cell containing little or no free fluid electrolyte. Semi-Permeable Membrane : A porous film that will pass selected ions. Short Circuit Current : The initial value of the current obtained from a cell/mono-block or battery in a circuit of negligible resistance. Service Life : The period of useful life of a cell/mono-block predetermined end-point voltage is reached. Separator : An ion permeable. Standby Battery : A battery designed for emergency use in the event of a main power failure.
. Reference Electrode : A specially chosen electrode which has a reproducible potential against which other electrode potentials may be referred. Series connections increase the voltage of the resultant battery as follows : Vs = n X Vu Where Vs is the resultant voltage. n is the number of cells/mono-blocks or batteries connected in series & Vu is voltage of the each cell/mono-block or battery. This enables gases to reach electrode surfaces during charging and facilitates gas recombination.
Voltage Delay : Time delay for a cell/mono-block or battery to deliver the required operating voltage after it is placed under load. balancing losses through a local action and/or periodic discharge. Trickle Charge : A charge at a low rate. Watt Hour (WH) Capacity : The quantity of electrical energy measured in watt hours which may be delivered by a cell/mono-block or battery under specified conditions. Thermal Runaway : A condition whereby a cell/mono-block or battery on charge or discharge will overheat and destroy itself through internal heat generation caused by high overcharge or over discharging current or other abusive condition. Watt Hour (WH) Efficiency : The ratio of the watt hours delivered on discharge of a battery to the watt hours needed to restore it to its original state under specified conditions of charge and discharge. Vented Cell/mono-block : A cell/mono-block design incorporating a vent mechanism to relieve excessive pressure and expel gases that are generated during the operation of the cell/mono-block. Large crystals of lead sulphate grow and interfere with function of the active materials. Working Voltage : The typical voltage or range of voltage of a cell/mono-block or battery during discharge. to maintain a cell/mono-block or battery in a fully charged condition.MONITORING OF VRLA BATTERIES GUIDELINES
Sulphation : Process occurring in lead batteries that have been stored & allowed to self-discharge for extended periods of time. Vent : A normally sealed mechanism which allows for the controlled escape of gases from within a cell/mono-block. The percentage WH efficiency is the product of AH efficiency & the ratio of average discharge and recharge voltage. Voltage Efficiency : The ratio of average voltage during discharge to average voltage during recharge under specified conditions of charge and discharge.
. Wet Shelf Life : The period of time that a cell/mono-block or battery can stand in the charged or activated condition before deteriorating below a specified capacity.
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1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 A or Amps AC AH BIS BSNL CACT dB dBA DC °C DG Emf FSD GR Hz IS Kg LED LCD mA MOV MTBF MTNL ms mV PF QA QM SMPS T&D V VRLA WH Amperes Alternate Current Ampere Hour Bureau Of Indian Standards Bharat Sanchar Nigam Limited Component Approval Centre of Telecommunication Decibel Decibel Absolute Direct Current Degrees Celsius Diesel Generator Electro motive force Full Scale Deflection Generic Requirements Hertz Indian Standards Kilo Grams Light Emitting Diodes Liquid Crystal Device mili Amperes Metal Oxide Varistor Mean Time between Failures Mahanagar Telephone Nigam Limited Mili seconds Mili Volts Power factor Quality Assurance Quality Manual Switch Mode Power Supply Technical & Development Volts Valve Regulated Lead Acid Watt Hour
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