ULTIMA SLM Ni-Cd BATTERYTECHNICAL MANUAL

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1. Introduction 3

2. Battery applications 4

3. Principles of the oxygen recombination cycle 5

4. Construction features of the Ultima battery 7

4.1 Plate assembly 7

4.2 Separation 8

4.3 Electrolyte 8

4.4 Terminal pillars 8

4.5 Venting system 8

4.6 Cell container 8

5. Benefits of the Ultima battery 9

6. Operating features 10

6.1 Capacity 10

6.2 Cell voltage 10

6.3 Internal resistance 10

6.4 Effect of temperature on performance 11

6.5 Short-circuit values 11

6.6 Open circuit loss 12

6.7 Cycling 12

6.8 Water consumption 12

6.9 Gas evolution 13

7. Battery charging 14

7.1 Charging methods 14

7.2 Charge acceptance 15

7.3 Temperature effects 16

7.4 Commissioning requirements 187.4.1 Batteries filled and charged7.4.2 Batteries filled and discharged

8. Special operating factors 19

8.1 Electrical abuse 198.1.1 Ripple effects8.1.2 Over-discharge8.1.3 Overcharge

8.2 Mechanical abuse 198.2.1 Shock loads8.2.2 Vibration resistance8.2.3 External corrosion

9. Battery sizing principles 20

10. Installation and storage 21

10.1 Emplacement 21

10.2 Ventilation 22

10.3 Storage 22

11. Maintenance of Ultima batteries in service 23

12. Refurbishment of Ultima batteries 24

13. Disposal and recycling 25

C ontents

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The nickel-cadmium battery is the mostreliable battery system available in themarket today. Its unique features enableit to be used in applications andenvironments untenable for other widelyavailable battery systems. With theadvent of the valve regulated lead acidbattery a new concept was available tothe customer, a battery that did notrequire water replenishment. However,this was obtained at the cost of reliability.To give the customer a highly reliablebattery of zero or ultra low maintenanceSaft have developed the Ultimarecombination pocket plate battery.

This publication details the design andoperating characteristics of theSaft Nife brand Ultima battery to enablea successful battery system to beachieved. A battery which in normalapplications requires no topping-up buthas all the well proven advantages of thenickel-cadmium pocket plate battery.

1 Introduction

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Ultima batteries are designed to meet theneeds of applications requiring thetraditional high reliability ofnickel-cadmium pocket plate cells withoutthe need to top-up with water. They areindeed the best solution for installations,whether they are UPS systems,emergency lighting systems,telecommunications, where the risk offailure of the system is unacceptable.Ultima batteries are also eminentlysuitable for “remote” applications such asphotovoltaic systems, offshoreapplications and switching substations,where the system must have totalreliability without the need for batterymaintenance.

● Offshore oil and gas● Fire and security systems● Process control● Telecommunications● Mass transit● Emergency lighting● Railway signaling● Switchgear● Photovoltaics● UPS

2 Battery applications

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In a conventional flooded electrolytepocket plate nickel-cadmium batterywater is lost from the battery onovercharge due to the followingreactions:

At the positive plate

40H- 2H20 + 02 + 4e-

(Oxygen evolution)

At the negative plate

4H20 + 4e- 2H2 + 40H-

(Hydrogen evolution)

This corresponds to a theoretical loss of36 g of water for 107Ah of overchargei.e. 0.335 cc per Ah. Hence aconventional cell requires periodicaddition of water. The frequency of thisoperation depends upon the cumulativeamount of charge received and theoperating temperature.

During the charging process evolution ofoxygen begins to occur a little before thepositive plate reaches its fully chargedstate and then becomes the mainreaction when the fully charged conditionis reached. However, the cadmiumnegative plate has a better chargeacceptance than the positive plate andhydrogen is not evolved until this plate isvirtually fully charged.

The Ultima battery has been designedwith an excess of cadmium negativematerial to enhance this effect andensure that oxygen evolution commencesprior to hydrogen evolution.

The oxygen which is produced at thepositive plate surface is collected by thespecial porous separator and thus notallowed to escape from the regionbetween the plates. Some displacementof electrolyte within the separator occurs,thus generating extra unfilled pores forthe diffusion of oxygen directly to theadjacent cadmium negative plate.

3 Principles of the oxygen recombination cycle

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As soon as the oxygen reaches thenegative plate it reacts either chemically:

2Cd + 02 + 2H20 2Cd(OH)2 (A)

or electrochemically:

02 + 2H20 + 4e- 40H- (B)

Reaction (A) has the effect of chemicallydischarging some of the cadmium tocadmium hydroxide. The current passingthrough the battery is used to rechargethis material.

Reaction (B) consumes the current directly.Thus hydrogen evolution at the negativeplate is suppressed because the preferredreaction is oxygen recombination. Hencethe total process of oxygen generationand consumption is referred to as anoxygen recombination cycle.

The efficiency of this oxygenrecombination process depends upon therelationship between the rate at whichoxygen is produced and the rate at whichit can be collected and transferred to thenegative plate surface. The rate ofcollection and transfer of oxygen iscontrolled by the separator type and thecell design.

The rate at which oxygen is produced onovercharge is directly related to thecharge current once the positive platehas reached a full state of charge. Thecharge current in turn is controlled by thecharging voltage level set on thecharging equipment and the ambienttemperature. By controlling the chargevoltage high efficiencies can be obtainedand in this way the rate of water loss canbe reduced to a fraction of that fromconventional batteries.

Though the efficiency of this oxygenrecombination is high it will neverachieve 100% as small quantities ofoxygen will escape from the separatorbefore reaching and reacting at thenegative plate. Thus a small quantity ofhydrogen will ultimately be generatedand hence a low rate of water loss willoccur. The battery is designed toaccommodate this by provision of agenerous electrolyte reserve both aboveand around each cell pack within thebattery. This ensures a long service lifewithout the need to top-up with water.

The Ultima battery is fitted with a lowpressure vent on each cell. Onovercharge the cells have an internalpressure above atmospheric pressure.The vent provides an outlet for therelease of small quantities of hydrogenand non-recombined oxygen and thuscontrols the internal pressure. When thepressure falls below the release pressureeither on open-circuit or on discharge thevent reseals to prevent ingress of air andminimize self-discharge reactions.

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Clip on cover

Terminal pillars

Plate group busbar

Polypropylene cell container

Polypropylene fibrous separator

Low pressureflame-arresting vent

Pocket plate

Plate group busbar

4.1 Plate assembly

The nickel-cadmium cell consists of twogroups of plates, one containing nickelhydroxide (the positive plate) and theother containing cadmium hydroxide (thenegative plate).

The active materials of the Saft Ultimapocket plate are retained in pocketsformed from nickel-plated steel strips

double perforated by a patented process.These pockets are mechanically linkedtogether, cut to the size corresponding tothe plate width and compressed to thefinal plate dimension. This process leadsto a component which is not onlymechanically robust but also retains itsactive material within a steel boundarywhich promotes conductivity andminimizes electrode swelling.

These plates are then welded to acurrent carrying busbar which furtherensures the mechanical and electricalstability of the product.

The alkaline electrolyte does not reactwith steel, which means that thesupporting structure of the Ultima batterystays intact and unchanged for the life ofthe battery. There is no corrosion and norisk of “sudden death”.

4 Construction features of the Ultima battery

The construction of theSaft Nife brand Ultima cell isbased upon the proven Saftpocket plate technology but withspecial features to enhance thelow water usage by means of therecombination cycle.

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4.2 Separation

As described in section 3, the separatoris a key feature of the Ultima battery. It ispolypropylene fibrous material which,after exhaustive analysis of availableseparator material, was speciallydeveloped for this product to give thefeatures required.

Using this separator and plastic spacingribs, the distance between the plates iscarefully controlled to give the necessarygas retention to provide the level ofrecombination required.

By providing a large spacing between thepositive and negative plates and agenerous quantity of electrolyte betweenplates, the possibility of thermal runawayis eliminated.

4.3 Electrolyte

The electrolyte used in Ultima, which is asolution of potassium hydroxide andlithium hydroxide, is optimized to give thebest combination of performance, lifeand energy efficiency over a widetemperature range.

The concentration is such as to allow thecell to be operated down to –20°C (forlow temperature operation see section 5)and it is not necessary to change theelectrolyte during the life of the cell.

It is an important consideration ofUltima, and indeed of allnickel-cadmium batteries, that theelectrolyte does not change duringcharge and discharge. It retains its abilityto transfer ions between the cell platesirrespective of the charge level.

4.4 Terminal pillars

Short terminal pillars are welded to theplate busbars using a well proven batteryconstruction method. These posts aremanufactured from steel bar, internallythreaded for bolting on connectors andare nickel-plated.

The terminal pillar to lid seal is providedby a compressed visco-elastic sealingsurface held in place by compressionlock washers. This assembly is designedto provide satisfactory sealing throughoutthe life of the product.

4.5 Venting system

Ultima is fitted with a low pressureflame-arresting vent for each cell of thebattery. This vent operates as a one wayvalve which will allow the release ofsmall quantities of hydrogen andnon-recombined oxygen if the internalpressure exceeds a fixed safety value.The nominal operating pressure of thevent is 0.2 bar.

When the pressure falls below the releasepressure the vent reseals to preventingress of air.

The sealing vent has an integralflame-arresting porous disk to preventany possibility of any external ignitionfrom spreading into the Ultima cell.

4.6 Cell container

Ultima is built up using the well provenSaft block battery construction. The toughpolypropylene containers are weldedtogether by heat sealing. Additional endwalls are welded on to constrain thesmall internal pressure changes createdby the recombination process and thelow pressure vent.

The assembly of the blocks is completedby a clip on cover enclosing the top ofthe Ultima block, giving anon-conducting, easy to clean, topsurface.

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The benefits of the Saft valve regulatedUltima battery are:

Complete reliability

Does not suffer from the sudden deathfailure due to internal corrosionassociated with other batterytechnologies.

Exceptional long life

Has all the design features associatedwith the conventional Saft twenty plusyears’ life battery products.

Ultra low maintenance

Ultima will give up to twenty yearswithout topping-up in normalapplications but can be engineered forsevere applications to give prolongedultra low maintenance with the option ofwater replenishment as and whenrequired.

Office compatibility

The Saft Ultima battery is a valveregulated recombination product and itgives off imperceptible amounts of gasand no corrosive fumes.

Wide operating temperaturerange

The normal Ultima maximum operatingtemperature range is 0°C to +40°C.However, Ultima can survive extremes oftemperature from as low as–40°C to up to +60°C.

Resistance to mechanical abuse

Ultima is designed to have themechanical strength for use in bothstationary and mobile applications.

High resistance to electricalabuse

Ultima will survive abuses which willdestroy the valve regulated lead acidbattery. In particular, it has a resistanceto overcharging, deep discharging,short-circuits, and a tolerance to up to15% AC ripple.

Low installation costs

Ultima can be used with existingcharging systems, has minimal gasevolution without any corrosive vapors,uses corrosion-free polypropylenecontainers and has an easy boltedassembly system.

Well proven pocket plateconstruction

Saft has over 80 years of manufacturingand application experience with thenickel-cadmium pocket plate productand this expertise has been built into thetwenty plus years’ design life of theUltima product.

5 Benefits of the Ultima battery

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6.1 Capacity

The Ultima battery capacity is rated inampere hours (Ah) and is the quantity ofelectricity which it can supply for a5 hour discharge to 1.0 V/cell afterbeing fully charged. This figure is inagreement with the IEC623 standard.

In practice, Ultima is used in floatingconditions and so the tabular data isbased upon cell performance afterseveral months of floating. Thiseliminates certain correction factorswhich need to be used when sizingbatteries with conventional fully chargedopen cell data (see section 9 – Batterysizing principles).

6.2 Cell voltage

The cell voltage of nickel-cadmium cellsresults from the electrochemicalpotentials of the nickel and the cadmiumactive materials in the presence of thepotassium hydroxide electrolyte. Thenominal voltage is 1.2 V.

6.3 Internal resistance

The internal resistance of a cell varieswith the type of service and the state ofcharge and is, therefore, difficult todefine and measure accurately.

The most practical value for normalapplications is the discharge voltageresponse to a change in dischargecurrent.

The internal resistance per 1/C5 of anUltima cell at room temperature whenmeasured after float charging at normaltemperature is 80 milliohms for SLM 8 to SLM 48 cells and 100 milliohms forSLM 71 to SLM 476 cells; e.g. for anUltima cell type SLM 8 (8 Ah) the internalresistance is 80x1/8 = 10 milliohms.

The above figures are for fully chargedcells. For lower states of charge thevalues increase.

For cells 50% discharged the internalresistance is about 20% higher and when90% discharged it is about 80% higher.The internal resistance of a fullydischarged cell has very little relevance.

6 Operating features

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Reducing the temperature also increasesthe internal resistance and, at 0°C, theinternal resistance is about 40% higherthan at room temperature.

6.4 Effect of temperature onperformance

Variations in ambient temperature affectthe performance of Ultima and thisneeds to be taken into account whensizing the battery.

Low temperature operation has the effectof reducing the performance but thehigher temperature characteristics aresimilar to those at normal temperatures.The effect of temperature is moremarked at higher rates of discharge.The factors which are required in sizing abattery to compensate for temperaturevariations are given in a graphical formin Figure 1 for the normal recommendedoperating temperature range of0°C to 40°C.

For use at temperatures outside thisrange please contact Saft for advice.

6.5 Short-circuit values

The typical short-circuit value in amperesfor an Ultima cell is approximately15 times the ampere-hour capacity.

The Ultima battery is designed towithstand a short-circuit current of thismagnitude for many minutes withoutdamage.

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6.6 Open circuit loss

The state of charge of Ultima on opencircuit slowly decreases with time due toself-discharge. In practice this decrease isrelatively rapid during the first two weeksbut then stabilizes to about 2% per monthat 20°C.

The self-discharge characteristics of anickel-cadmium cell are affected by thetemperature. At low temperatures thecharge retention is better than at normaltemperature and so the open circuit lossis reduced. However, the self-discharge issignificantly increased at highertemperatures.

The open circuit loss for Ultima for thestandard temperature and the extremesof the normal operating range is shownin Figure 2 for a one year period.

It is necessary to recharge Ultima eachyear for storage periods in excess of oneyear.

6.7 Cycling

Ultima is an ultra low maintenanceproduct and therefore is used generallyin standby and not continuous cyclingapplications. Nevertheless, it is designedusing conventional pocket plate electrodetechnology and has therefore anequivalent cycling capability to thestandard product.

If Ultima is used in a deep cyclingapplication which requires a fastrecharge, there will be significant gasevolved and the ultra low maintenanceproperties of the product will be severelyreduced. However, there are cyclingapplications where Ultima can bebeneficial. This will depend on thefrequency and depth of dischargeinvolved.

6.8 Water consumption

The Ultima battery works on the oxygenrecombination principle and thereforehas a much reduced water consumption.In practice, for the recommendedcharging voltages, Ultima has a level ofrecombination of 85% to 95%. Thiscompares to the level of recombination

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found in equivalent vented pocket platecells of 30% to 35%. Thus Ultima has awater usage reduced by a factor of up to10 times of that of an open flooded cell.This means that at suitable chargingvoltages and temperatures, Ultima willnot need water replenishment for morethan 20 years.

However, not all needs are the same andUltima is designed to allow waterreplenishment under different and moredifficult charging conditions. Figure 3gives a comparison of different waterreplenishment times under different floatvoltages at 20°C.

6.9 Gas evolution

The gas evolution is a function of theamount of water electrolyzed intohydrogen and oxygen which is notinvolved in the recombination cycle. Theelectrolysis of 1 cc of water producesabout 2000 cc of gas mixture and thisgas mixture is in the proportion of

2/3 hydrogen and 1/3 oxygen. Thus theelectrolysis of 1 cc of water producesabout 1300 cc of hydrogen.

As stated in the previous paragraph,under normal recommended floatconditions Ultima has a recombinationlevel of 85% to 95% and so the amountof water which is electrolyzed into gas issmall. Typically an Ultima cell willelectrolyze about 0.002 cc of waterper Ah of cell capacity per day. This value will be smaller or largerdepending on the float voltage value.Thus a typical value of gas emissionwould be 3.5 cc per Ah of cell capacityper day, or 2.5 cc of hydrogen per Ah ofcell capacity per day.

To put this into perspective this meansthat a 50 Ah Ultima cell will produce inone year a hydrogen volume equivalentof a child’s balloon.

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In order to ensure that the ultra lowmaintenance properties of the Ultimabattery are achieved, it is necessary tocontrol the charge input to the battery tominimize the rate of water loss during thelife of the product.

It is important therefore that therecommended charge conditions arecomplied with.

However, Ultima is unique inrecombination valve regulated systems inallowing the possibility of replenishmentof water in severe applications whereexcessive water loss is unavoidable.

7.1 Charging methods

Ultima batteries may be charged by thefollowing methods:

a) Two level constant potentialcharging:

The initial stage of two rate constantpotential charging consists of a firstcharging stage, with a current limit of0.1 C5 to an average maximum voltageof 1.45 V/cell.

Alternatively, if a faster rate of rechargeis required, a voltage limit of 1.55 V/cellcan be used. However, if frequentrecharges are required this will increasethe rate of water loss.

After this first stage the charger shouldbe switched to a second maintenancestage at a float voltage in the range of1.41 to 1.43 V/cell. After a prolongedmains failure the first stage should bereapplied manually or automatically.

b) Single level float charging

Ultima batteries may be float charged at1.41 to 1.43 V/cell from a fullydischarged condition to a high stage ofcharge. This is detailed in section 7.2and about 80% of the capacity will beavailable after 16 hours of charge.

Alternatively, Ultima can be float chargedat 1.45 V/cell if a faster recharge time isrequired. This will, however, increase therate of water loss and reduce themaintenance interval by a factor of two.

Temperature compensation may berequired as described in section 7.3.

7 Battery charging

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7.2 Charge acceptance

The performance data sheets for Ultimaare based upon several months’ floatingand so are for fully float charged cells.

A discharged cell will take a certain timeto achieve this and Figure 4 gives thecapacity available for the two principalcharging voltages recommended forUltima, 1.42 V/cell and 1.45 V/cell,during the first 30 hours of charge froma fully discharged state.

If the application has a particularrecharge time requirement then this mustbe taken into account when calculatingthe battery (see section 9 – Battery sizingprinciples).

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7.3 Temperature effects

The recombination efficiency of theUltima cell is dependent on the floatingcurrent and this, in itself, is a function ofthe floating voltage. Thus the floatingvoltages chosen for Ultima are carefullyoptimized at an ambient temperature of20°C between the current required tocharge the cell and the level of currentrequired to give the ultra lowmaintenance features.

As the temperature increases then theelectrochemical behavior becomes moreactive and so, for the same floatingvoltage, the current increases. As thetemperature is reduced then the reverseoccurs. Increasing the current increasesthe water loss and reducing the currentcreates the risk that the cell will not besufficiently charged. Thus as it is clearlyimportant to maintain the same currentthrough the cell, it is necessary to modifythe floating voltage as the temperaturechanges.

The change in voltage required, or “temperature compensation”, is given in Figure 5. If these valuescannot be exactly met with a particularsystem then temperature compensationvalues of between –2.5 mV/°C and–3.5 mV/°C are acceptable.

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The effect of increasing the continuousambient temperatures is shown inFigure 6. For a continuous ambienttemperature of 40°C the waterconsumption is doubled with respect to20°C. If temperature compensation isused then this is largely eliminated,although not entirely as, at hightemperatures, the gas occupies a largervolume and so it is less easily retainedby the separator.

In practice, for a continuous ambienttemperature of 20°C with fluctuationsup to 30°C and down to 10°C,temperature compensation for thecharger is not necessary as there issufficient safety margin in the productdesign to allow for these fluctuations.

However, for ambient temperaturesoutside 15°C to 25°C or fortemperature fluctuations beyond the10°C to 30°C it is recommended thatthe temperature compensation shouldbe used.

If the temperature range of theapplication is outside the operatingrange of 0°C to 40°C or the ambienttemperature is outside 15°C to 25°Crange and temperature compensationis not feasible, it is still possible thatUltima can be used but with somemodification to voltages andmaintenance interval. Under thesecircumstances please contact Saft forassistance.

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7.4 Commissioning requirements

7.4.1 Batteries filled and charged

Ultima batteries are normally suppliedcharged, ready for immediate use and,provided they have not been stored formore than six months, they may be putdirectly into service on float charge. Under these circumstances they shouldnot be given a commissioning chargebefore putting into service.

Batteries stored between six and twelvemonths should be treated as batteriesfilled and discharged - section 7.4.2

7.4.2 Batteries filled anddischarged

Ultima batteries in a filled anddischarged state require acommissioning charge prior to puttinginto service. This is a once only operationand is essential to prepare the battery forits long service life.

The commissioning charge requires aninput of 160% of the rated (C5) capacitybefore putting the battery into service.

Prolonged overcharging is not harmful toUltima batteries but will reduce the initialelectrolyte reserve and thus the servicelife without topping-up. In the event ofovercharge in excess of thisrecommendation, the level of electrolytecan be checked and restored to themaximum level.

The following methods of commissioningcharge are recommended:

a) Charge 16 hours at 0.1 C5 Amaximum.

b) Charge at 1.65 V/cell for 16 hoursmaximum (0.1 C5 A current limit).

If these recommended methods are notavailable in practice, then charging maybe carried out at lower float voltages forextended periods.

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8.1 Electrical abuse

8.1.1 Ripple effects

The nickel-cadmium battery is tolerant tohigh ripple from standard chargingsystems. Ultima has been tested withvoltage ripple values of up to 15%without any effect on water loss.

8.1.2 Over-discharge

If more than the designed capacity istaken out of a battery then it becomesover-discharged. This is considered to bean abuse situation for a battery andshould be avoided.

In the case of lead acid batteries this willlead to failure of the battery and isunacceptable.

The Ultima battery is designed to makerecovery from this situation possible.

8.1.3 Overcharge

Overcharge of a recombination batteryleads to an excessive use of water.

In a restricted electrolyte battery, such asvalve regulated lead acid, this loss ofelectrolyte is irreversible and will lead topremature failure of the battery.

In the case of Ultima, with its generouselectrolyte reserve, a small degree ofovercharge will not significantly alter themaintenance period. In the case ofexcessive overcharge, a situation whichwill immediately destroy a valveregulated lead acid battery, Ultima can be refurbished as describedin Section 12.

8.2 Mechanical abuse

8.2.1 Shock loads

The Ultima block battery concept hasbeen tested to both IEC 68-2-29 (bump tests at 5 g, 10 g and 25 g) andIEC 77 (shock test 3 g).

8.2.2 Vibration resistance

The Ultima block battery concept hasbeen tested to IEC 77 for 2 hours at 1 g.

8.2.3 External corrosion

Ultima nickel-cadmium cells aremanufactured in durable polypropylene,all external metal components arenickel-plated and these components areprotected by a neutral grease and a rigidplastic cover.

8 Special operating factors

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Ultima is designed to be easy to useand specify and so the published datais based on cells which have been onfloat for several months, i.e. the datareflects the practical situation.

Thus in a situation at normal ambienttemperature without any specificrequirement with regard to rechargetime the published data can be useddirectly to size the battery. However, ifthere are requirements with regard torecharge time or temperature thenthis will modify the result.

Examples

A standby system is to be sited in abuilding with an ambient temperatureof 20°C and the temperature willalways lie between 10°C and 30°C. Ithas a maximum voltage of 130 Vand a minimum voltage of 95 V andrequires a back-up of 105 A for2 hours.

In this case a simple 1.42 V/cellsingle level charger withouttemperature compensation canbe used.

Number of cells = 130/1.42 = 91and the final voltage will be 95/91 = 1.04 V/cell.

The Ultima data shows that theSLM 238 gives 109 A for 2 hours to1.05 V/cell and so the battery wouldbe 91 cells of SLM 238. At this singlelevel voltage and at this temperaturethe battery would give 20 yearswithout topping-up.

However, if for this example there wasa restriction that the battery must give80% of its performance after 10 hoursfrom a totally discharged state thencertain modifications need to bemade to the calculation.

If the single level 1.42 V/cell chargeris retained, then from Figure 4 it canbe seen that after 10 hours about74% of the capacity is available andso the battery size will have to beincreased by the factor 80/74 or, inother words, 8%. Thus for a current of113 A (105 A + 8%) to 1.05 V/cellthe battery required is 91 cells ofSLM 285 as this gives 131 A to1.05 V/cell. This battery will still givethe 20 years without topping-up.

From Figure 4, it can be seen that avoltage of 1.45 V/cell gives 80% ofthe capacity after 10 hours and sothere is no need to increase the cellcapacity to compensate for thecharge. However, the battery has tobe recalculated as, with the samevoltage window, the higher chargevoltage will modify the end ofdischarge voltage.

Thus, the number of cells =130/1.45 = 89 and so the end ofdischarge voltage becomes95/89 = 1.07 V. The Ultimaperformance table gives for 2 hoursdischarge at 117 A to 1.10 V/cell theSLM 285, and so in this case thebattery is 89 cells of SLM 285.

The disadvantage of this solution isthat a single level charger of 1.45 V/cell will only give 10 yearswithout maintenance and so toachieve the 20 year maintenancelevel a two stage charger is required.

In principle it is always better to go tothe lowest charge voltage as thisgives the lowest end of dischargevoltage, and generally a smaller cellcapacity for the same duty, and givesthe best maintenance interval.

Temperatures outside the standardrange are treated in precisely thesame way using Figure 1 for thede-rating factors.

When treating temperatures it isimportant to note that lowtemperatures reduce the performance(Figure 1) and so the battery sizemust be increased to accommodatethis and at higher temperatures theultra low maintenance is reduced(Figure 6) and so specialconsideration should be given tocharging parameters.

This section is intended to givegeneral guidelines in battery sizing.For advice on special batteryapplications contact Saft.

9 Battery sizing principles

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10.1 Emplacement

The Saft Nife brand Ultimavalve regulated recombination batterycan be fitted onto stands, can be floormounted or can be fitted into cabinets.

Local standards or codes normally definethe mounting arrangements of thebatteries, and these must be followed ifapplicable. However, if this is not thecase the following comments can beused as a guide.

When the battery is housed in a cubicleor enclosed compartment it is necessaryto provide adequate ventilationdepending on utilization (see section10.2 – Ventilation).

Allow sufficient space over the battery toensure easy access during assembly.

Saft offers a wide selection of stands tosuit most applications.

It is desirable to have easy access to allblocks on a stand mounted battery andthey should be situated in a readilyavailable position. Distances betweenstands, and between stands and walls,should be sufficient to give good accessto the battery.

The overall weight of the battery must beconsidered and the load bearing on theflooring taken into account in theselection of the battery accommodation.In case of doubt, please contact Saft foradvice.

When mounting the battery ensure thatthe cells are correctly interconnected withthe appropriate polarity. The batteryconnection to load should be withnickel-plated cable lugs. The connectorsand terminal screws should be corrosionprotected by coating with a thin layer ofnatural vaseline or anti-corrosion oil.

Recommended terminal bolttightening torques are:

Cell Recommended connection torque

bolt per pole N.m Ibf.in

M 6 11 99M 8 20 180M 10 30 270

To avoid accelerated ageing of the plasticdue to UV light, batteries should not beexposed to direct sunlight, UV lightsources or strong daylight for prolongedperiods.

10 Installation and storage

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10.2 Ventilation

Under normal floating conditions theSaft Ultima battery gives off up to 10 timesless gas than a conventional open cell.Thus the need for ventilation is muchreduced and in many cases no specialventilation requirements other than normalroom ventilation are required. The quantityof hydrogen given off is given in section6.9, Gas evolution. However, if the Ultimabattery is commissioned in the finallocation or if the maximum recommendedcharge current of 0.1 C5 is used then thequantity of gas given off will be increased.

A typical figure for room ventilation isabout 2.5 air changes per hour and undersuch conditions it is satisfactory to install700 watt hours of battery capacity percubic meter if the final charge current is at0.1 C5 A.

Please refer to ventilation standards andrequirements applicable in your countryor area.

Care should also be taken with cubicleinstallations to ensure sufficient ventilationand battery spacing to prevent overloadingand, hence, excess water usage.

10.3 Storage

Ultima batteries are normally supplied filledwith electrolyte and charged ready forimmediate use. They may be stored in thiscondition for up to twelve months from thedate of despatch from Saft.

If batteries are not put into serviceimmediately, they should be stored in aclean, dry, cool (+10°C to +30°C) andwell ventilated store on open shelves. Theyshould not be exposed to direct sunlight.Before storage ensure that the batteries areclean, with an adequate protective finish,such as an approved neutral grease,on the connectors, and that theflame-arresting low pressure vents remainundisturbed.

Batteries filled and charged can be storedfor up to one year without any conditioningcharge requirement. If they are stored upto six months they should be put directlyinto service without any commissioningcharge. If they have been stored forbetween six months and one year theyshould be given a commissioning chargeas described in section 7.4.

Before putting into service ensure that thebatteries are externally clean and with anadequate protective finish, such as anapproved neutral grease, on theconnectors.

If it is necessary to store the batteries formore than one year then they should begiven the following conditioningdischarge / charge cycle at the end ofeach year of storage.

� Discharge at 0.1 C5 A to an end ofdischarge voltage of 1.1 V/cell, whereC5 is the rated capacity of the battery.

� Charge 160% battery’s rated capacity ata maximum of 0.1 C5 A for 16 hours.

� Return battery to store.

� Repeat every 12 months.

All batteries after storage must be preparedfor service and fully commissioned asdescribed for cells after one year’s storage.

Storage at temperatures above+30°C can result in loss of capacity.This can be as much as 5% per 10°Cabove +30°C per year.

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In a correctly designed standbyapplication Ultima is a maintenance freeproduct and requires the minimum ofattention. However, it is good practicewith any standby system to carry out afull discharge / charge cycle once peryear to ensure that the charger, thebattery and the auxiliary electronics areall functioning correctly.

When this system service is carried out itis recommended that the Ultima celllevels should be checked visually toensure that the level is above theminimum, the batteries should bechecked for external cleanliness and ifnecessary cleaned with a damp cloth andthat the cover should be removed tocheck that the protective grease on theterminals remains intact and that thevents are clean.

If there is evidence that electrolyte hasbeen ejected from the vents or that therehas been an excessive use of water, thiscould indicate a charger or systemmalfunction. Action should be taken torectify this.

Please note that, when checking thelevels, a fluctuation in level betweenadjacent cells is not abnormal and is dueto the different levels of gas held in theseparator of each cell.

11 Maintenance of Ultima batteries in service

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12 Refurbishment of Ultima batteries

Refurbishment of the Ultima battery isrecommended when the electrolyte levelreaches the normal minimum mark onthe cell but must be carried out before itreaches the warning level on the cell.Batteries operated at float charge ratesabove 1.42 V/cell will requirerefurbishment during their operating life(see section 6.8 – Water consumption).

Refurbishing of the Ultima battery iscarried out as follows:

� Disconnect the battery from the load.Remove the orange terminal cover.

� With the terminal cover removed, thetops of the individual cells of theUltima battery will be in view.

� Confirm that an adequate protectivefinish (recommended neutral grease)remains on glands, poles andconnectors. Replenish if necessary.

� Carefully loosen the flame-arrestinglow pressure vents to release any gaspressure and then remove each ventcompletely and retain for refitting.

� Top-up each cell with distilled orde-ionized water to the specifiedmaximum level. Saft can supplyspecial topping-up equipment onrequest.

� Wipe up any small spillage on cellsusing a clean cloth. Replace the ventstaking care to tighten them correctlyi.e. until resistance against a stop isexperienced, and ensure that theseating rubber has not beendisturbed out of position. If there isany doubt about the quality of thesealing ring replace with a new ventassembly.

� Replace the orange terminal cover.

The refurbished Ultima cell is now readyfor recommissioning (see section 7.4.2 –Commissioning requirements: batteriesfilled and discharged).

Note: Before proceeding with any batteryrefurbishment please ensure that theSafety Precautions given in the UltimaOperating Instruction Sheet arecomplied with.

25

When a nickel-cadmium battery reachesthe end of its long service life, Saftstrongly recommends its return for fullrecycling. The simple and unique naturesof the battery’s components make themreadily recyclable.

A network of Saft collection sites operatesworldwide. If you use a small number ofcells or batteries you may transport themto one of these sites. From there they willbe sent to Saft’s Oskarshamn or otherapproved recycling plants for propertreatment.

Ni-Cd batteries must not be discarded asharmless waste. In most countries, usersare legally responsible for their safedisposal. These batteries contain heavymetals with a corrosive liquid and must

be treated carefully in accordance withlocal and national governmentregulations.

If you intend to handle spent batteriesyou should familiarise yourself withregulations governing reportable storagequantities and allowable storage periods.Your local Saft representative can assistyou with full information on theseregulations and the whole recyclingprocedure.

Ask for other publications that providemore details on recycling industrialNi-Cd batteries:

Industrial Ni-Cd batteries and theenvironment – Your questions answered

Recycling of industrial Ni-Cd batteries

NICKELPLATES

STEELSCRAP

CADMIUMPLATES

DISTILLATION

PURECADMIUMDISMANTLING

STEELWORKS

NEWBATTERIES

BATTERYUSE

SPENTBATTERIES

CADMIUMPLATES

13 Disposal and recycling

ArgentinaSaft Argentina SA, Buenos AiresTel: +54 11 4 686 1995Fax: +54 11 4 684 1925

AustraliaSaft Pty Ltd, Seven HillsTel: +61 2 9674 0700Fax: +61 2 9620 9990

BrazilSaft Ltda., São PauloTel: +55 11 6100 6300Fax: +55 11 6100 6338

CanadaPlease contact USA office

Czech RepublicSaft Ferak a.s., PragueTel: +420 2 66094 819Fax: +420 2 66094 813

FranceDivision France, BagnoletTel: +33 (0)1 49 93 19 18Fax: +33 (0)1 49 93 19 50

GermanySaft GmbH, NürnbergTel: +49 911 94174-0Fax: +49 911 426144

Hong KongSaft Nife Ltd, KowloonTel: +852 2795 27 19Fax: +852 2798 05 77

ItalySaft S.p.A., Vimercate (Milano)Tel: +39 039 68 69 275Fax: +39 039 68 63 847

JapanSumitomo Corp., TokyoTel: +81 3 5144 9080Fax: +81 3 5144 9267

Middle EastSaft ME Ltd, Limassol, CyprusTel: +357 53 40 637Fax: +357 57 48 492

NetherlandsSaft BV, HaarlemTel: +31 23 750 5720Fax: +31 23 750 5725

NorwaySaft AS, OsteraasTel: +47 6716 4160Fax: +47 6716 4170

SingaporeSaft Pte Ltd, SingapourTel: +65 84 65 700Fax: +65 74 16 396

SpainSaft Iberica SL, MinanoTel: +34 94 521 4110Fax: +34 94 521 4111

SwedenSaft AB, OskarshamnTel: +46 491 68000Fax: +46 491 68180

United KingdomSaft Ltd, HainaultTel: +44 208 498 1177Fax: +44 208 498 1115

USASaft America Inc, Stationary batteriesNorth Haven, ConnecticutTel: +1 203 239 4718Fax: +1 203 234 7598

Railway batteriesCockeysville, MDTel: +1 410 771 3200Fax: +1 410 771 1144

Doc. No. RM07. 01-21036. 2Data in this document are subject to changewithout notice and become contractual onlyafter written confirmation.

Société anonyme au capital de 500 000 000 F -

RCS Bobigny B 343 588 737

Photo credit : Corbis, Digitalvision, Photodisc, Saft.

Produced by Arthur Associates - Printed in the UK

SaftIndustrial Battery Group12, rue Sadi Carnot -93170 Bagnolet - FranceTel: +33 (0)1 49 93 19 18Fax: +33 (0)1 49 93 19 50

www.saftbatteries.com