Technical manualinstallation, operation and maintenancefor Ni-Cd STM MR-MRE monoblocks type

Introduction 1

Important recommendations 2

1. Characteristics of STM MR-MRE monoblocks 1.1. General description 3

1.1.1. Operation principle of vented Ni-Cd cells 31.1.2. Description of STM MR-MRE Ni-Cd monoblocks 4

1.2. Mechanical characteristics 51.3. Electrical characteristics 51.4. Description of the centralized filling system 6

1.4.1. General description 61.4.2. Working principle of a centralized filling ramp 7

2. Precautions and practices 2.1. Transport, storage 82.2. Water and electrolyte 8

2.2.1. Water quality 82.2.2. Harm caused in using sulfuric acid or

acidic water 82.3. Electrical shocks and burns 92.4. Possible dangers of hydrogen 9

3. Installation 3.1. Assembly into batteries 103.2. Ventilation and cooling 113.3. Assembly of centralized water filling system 11

3.3.1. Precautions and recommendations 113.3.2. General instructions for assembly 12

Contents

4. Placing into service 4.1. Procedure before use 134.2. Commissioning cycle and water topping-up 13

5. Operation 5.1. Operating temperature 145.2. Two-level charge 14

5.2.1. Normal charge 145.2.2. Fast charge 145.2.3. Maintenance charge 145.2.4. Recommended charging method 15

5.3. Discharge 17 5.3.1. Discharge current 175.3.2. Voltage in discharge 17

6. Maintenance6.1. Periodic maintenance 186.2. Topping-up operation 18

7. Repair and overhaul of batteries7.1. Electrolyte specific density 197.2. Reconditioning 19

Appendix 1 STM 5-100 MR G RD equipped 20Appendix 2 STM 5-100 MRE G RD equipped 21Appendix 3 STM 5-140 MR G RD equipped 22Appendix 4 STM 5-140 MR D RG equipped 23Appendix 5 Accessories for the central filling system 24Appendix 6 Basic specification for filling circuit hoses 25Appendix 7 Basic specification for the cooling system hoses 26Appendix 8 Basic specification for rigid connections 27Appendix 9 Basic specification for distilled

or demineralized water 28

This manual is intended for users,technical and maintenancepersonnel.

It contains the main characteristicsof the low maintenance Saft Ni-CdSTM MR-MRE monoblocks.

It provides guidelines for use and maintenance to obtain thebest performance and a longuseful life.

The instructions are of generalvalidity for batteries in ElectricVehicles.

Nevertheless, every vehicle willhave a specific battery that hasbeen adapted to its ownmechanical, electrical, thermal,and other characteristics.

Depending on the referencedmodel, specific instructions mightbe added to this document.

For uses other than the onesdescribed in this manual,contact Saft.

Introduction

1

! Install the battery such as toensure good ventilation.

! Never allow a flame or fire tocome near the battery.

! The electrolyte is harmful tothe skin and particularly tothe eyes. In the event ofcontact with eyes, washimmediately with runningwater and/or with a 10 %solution of boric acid.

! Wear base-resistant gloves and goggles to manipulatethe electrolyte.

! Never use sulfuric acid oracidified water to top-upelectrolyte, as acid, even intraces, destroys the battery.

! Use tools with insulated handles.

! When batteries or vehiclesequipped with STM MR-MREbatteries are operated inclosed premises, natural orforced ventilation is necessary.Always respect the applicablesafety codes and regulationsof the country of operation.

Important recommendations

2

1.1. General description

1.1.1. Operation principle ofvented Ni-Cd cells

The electrochemistry concept ofthe batteries is to supply energy toelectrical and electronic products.Chemical energy stored in abattery is converted into electriccurrent when the batteryis discharged. This electric currentis produced directly by chemicalreactions that occur withinthe battery.

The nickel-cadmium cell is anelectrochemical system in whichthe electrodes containing theactive materials undergo changesin oxido-reduction state withoutany change in physical state. The active materials aresubmerged in alkaline electrolyte.They remain in solid state and do not dissolve during the oxido-reduction process. As a result,the electrodes are long-lived,since no chemical mechanismexists that might cause the lossof active materials.

When a battery is charged or discharged, the hydroxide ions (OH) are transferred from one electrode to the other via the electrolyte. The alkalineelectrolyte, a liquid solution ofpotassium hydroxide (KOH) andadditives, provides the means oftransport for the ions.

It does not participate in theelectrochemical reaction. Its rolein the operation being passive,the electrolyte is only remotelyaffected by the state of charge of the nickel-cadmium battery.

During overcharge, the watercontained in the electrolyte isdecomposed into oxygen andhydrogen.

In a low maintenance battery,a significant amount of thesegases recombines in the battery,thus reducing water consumption. The remaining amount leaves the cells through the hydraulicsystem. Consequently, theelectrolyte level is reduced after a certain number of chargingcycles and periodic topping-up ofthe battery with water becomesnecessary (chapter 6.2.).

1. Characteristics of STM MR-MREmonoblocks

3

4

1.1.2. Description of STM MR-MRE nickel-cadmiummonoblocks

The low maintenance STMmonoblock consists of 5 nickel-cadmium cells of 1.2 V nominalvoltage each. These 5 cells are assembled intoa polypropylene monoblockcontainer to obtain a nominalvoltage of 6 V.

The suffix MR indicates lowmaintenance and air cooling.

The suffix MRE indicates lowmaintenance and water cooling.

When the monoblocks aredelivered in single monoblockunits (not pre-assembled by Saftinto crates or boxes), themonoblock STM 5-140 MR issupplied with belt plates. In orderto decrease the weight of eachbattery unit during use, the beltplates of STM 5-140 monoblockscan be removed if the batterystructure (crates or boxes, etc.)provides sufficient mechanicalprotection against deformation ofthe small sides of the monoblocks(refer to chapter 3.).

The monoblock STM 5-100 MRand MRE’s do not haveindependent support plates. The support structure is integratedin the monoblock container.

The blocks will be assembled into a battery by serialinterconnection, in order toachieve the desired operationalvoltage. When the forced aircooling monoblocks are mountedinto a vehicle, sufficient spacealong the large sides must beprovided for correct cooling.

! Electrodes

The STM monoblocks areconstituted of sintered positiveelectrodes and plastic bondednegative electrodes.

The positive electrode is createdby chemical impregnation ofnickel hydroxide and additivesinto a sintered nickel structure,placed onto a perforated nickel-plated steel strip.

The negative electrode isobtained by pasting cadmiumoxide and a plastic bondingadditive onto a perforated nickel-plated steel strip.

Subsequently, a multi-layerseparator is placed between thepositive and the negativeelectrodes to form the plate-group.

! Electrolyte

The alkaline electrolyte in a nickel-cadmium battery is a liquidsolution of potassium hydroxide(KOH), lithium hydroxide (LiOH),or sodium hydroxide (NaOH) intodistilled or demineralized water.During the electrochemicalreactions, the physical density ofthe electrolyte remains practicallyconstant. Under no circumstancescan it be used as an indicator ofstate of charge.

Only overcharging will cause anormal water consumption and aslow concentration in the physicaldensity of the electrolyte.

The difference in density betweena charged and a dischargedbattery can be considered to benegligeable.

After topping-up of the battery,the density of the electrolyte is at

its lowest. After consumption ofthe electrolyte reserve, the densityof the electrolyte is at its highest.

The construction of a monoblockdoes not permit electrolytesampling of an STM batterywith integrated ramp withoutmechanical destruction of themonoblock. Measuring the densityof the electrolyte is thereforeimpossible.

! Separator

The separator of the STMmonoblocks is multilayer, non-woven and made ofpolypropylene. It was selected to satisfy the three principalobjectives: to be a good insulatorbetween the electrodes, to havethe right porosity for excellentelectric performance duringcharge and discharge, andensure the passage of oxygenions during charge to facilitate he recombination.

! Container

The monoblock container and the fluid chambers containing the cooling liquid, if present, aremade of polypropylene, as are the cover and the filling ramp that are welded to the containerafter the insertion and connectionof the battery plate-group and the electrolyte.

5

1.2. Mechanical characteristics

STM 5-100 STM 5-140 MRMR MRE with without

plates plates

Weight (kg) 12.9 13.2 18.4 17.0

Dimensions (mm). length 248 246 282 244. width 120 123 153 153. height 260 260 260 260

Electrolyte reserve 175 175 160 160(cm3)

Terminal M 8 x 1.25 M 8 x 1.25

Refer to attached diagram " / # $ / %

1.3. Electrical characteristics

STM 5-100 MR and MRE STM 5-140 MR

Rated capacity IEC 100 Ah 136 AhC/3

Nominal voltage Un 6 V 6 V

Apparent internal resistance(completely charged)at + 20°C 4 mΩ 4 mΩ

1.4. Description of thecentralized filling system

1.4.1. General description

This chapter describes theworking principle of the singlepoint water filling system used on STM monoblocks.

! Assembly instructions

see chapter 3.3.

! Operating instructions(topping-up)

see chapter 6.2.

The water filling system connectsa number of monoblocks inhydraulic series.

During normal operation of the battery, a significant amountof the gases produced duringovercharge recombines in thebatteries. The remaining gas isexhausted through the hydraulicsystem.

When topping-up of the batteryis necessary, water filling is donefrom a reservoir that feeds thebattery with a low-pressure pumpor through gravity. The topping-upis being effected cell by cell to apredetermined level. The filling ofan hydraulic system is completedwhen all batteries are filled andwater appears at the end of itshydraulic system. The filling of abattery is completed when allcells of the battery are filled.

The main component of thesystem is the water filling rampthat guarantees the evacuation ofthe gases, as well as the

automatic regulation of theelectrolyte level in each cellduring topping-up.

For a battery with severalhydraulic circuits, the topping-upwill be done separately for eachhydraulic circuit.

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7

1.4.2. Working principle ofa centralized filling ramp

The concept is to fill a cell withwater up to a specified level (N)allowing gas which is in the cell to escape. When the maximum levelis reached, the electrolyte closesthe gas exhaust tube and the

consequent excess pressure stops the water flow into the cell. The water will then flow to the nextcell and so on, to the last cell of thehydraulic circuit.

The centralized filling ramp is asoldered assembly of the monoblockcover (1) and a ramp (2) equippedon the upper part with a tubularwater inlet (3) and a tubular wateroutlet (4), and an exhaust tube (5)on the lower part (see fig.1 below).

The water flows across the rampthrough a plunging siphon (6) andinto the cell through the exhaust hole (7), while the air escapes through the exhaust tube (5). The lower edge of the gas exhausttube (5) settles the expectedelectrolyte level of the cell.

When the electrolyte reachesthis level, the remaining air in thecell can no longer escape throughthe gas exhaust tube (5) and the water reserve generated bythe plunging siphon (6) ensures a safe obstruction of the gasinside the cell. When the fillingof the cell is finished, the waterflows to the next cell or the nextmonoblock.

The centralized filling ramp has nomoving parts and offers fulloperational security. Further, thissystem prevents the cell electrolytefrom any contact with the next cell,thus avoiding any risk of currentleakage between several cells in a battery.

& Filling through gravity

The flow rate of the watermust be between 0.7 and 1 liter/minute and the relativepressure under 0.15 bar.

& Low pressure filling

The flow rate of the water must be lower than 0.7 liter/minuteand the relative pressure below0.3 bar.

Figure n° 1

8

2.1. Transport, storage

Low maintenance STM batteriesare delivered filled with electrolyteand electrically discharged. It isnormal that the electrolyte level isnot visible after a long storageand transport period, even in themonoblocks STM 5-100 MR and5-140 MR. It will become visibleduring charge (refer to chapter 4).

Depending on customerspecifications, low maintenanceSTM monoblocks can bedelivered completely assembledinto batteries, partly assembled,or as a kit of monoblocks andaccessories.

In the latter two cases, to avoidany spilling of electrolyte duringtransport, the monoblocks arefitted with transport plugs.

& Never drain the electrolyte inthe monoblocks

The battery units can be storedin whatever their state ofcharge. After a storage periodof more than one year, it isnecessary to carry out acommissioning charge beforeuse (see chapter 4.2.)

2.2. Water and electrolyte

The water and electrolyte usedin Saft Ni-Cd batteries must bechemically pure.

Under normal operatingconditions, it is neither necessarynor possible to change or addelectrolyte (KOH).

It is only a matter of readjustingwater that was consumed duringovercharges, in adjusting thelevels regularly (see chapter 6.2.).

& If monoblocks have lost theirelectrolyte by accident (drop,spills, mishandling, etc...) it may be necessary toreplenish the electrolyte. This can only be done in a Saft factory by Saft specialists.Please contact us without fail.

& Measuring the electrolytespecific density

The low maintenance STMmonoblocks that are equippedwith a centralized filling rampshould be considered sealed.Measuring or reconcentrating theelectrolyte density is impossible.

2.2.1. Water quality

lt is absolutely necessary thatchemically pure water, distilled or demineralized, is used fortopping-up (see appendix 9).Prevent the use of tap water asit contains impurities, that willadversely effect the electrolyte,operation quality, and the usefullife of the monoblocks. Storewater in hermetically sealedplastic containers.

2.2.2. Harm caused in usingsulfuric acid or acidious water

Sulfuric acid (as it is used inlead- acid batteries) seriouslydamages alkaline batteries.Never put sulfuric acid in nickel-cadmium batteries.

Also prevent the use of topping-upwater recommended for lead-acidbatteries since it may containsulfuric acid.

When in doubt about waterpurity, effect a litmus test (orequivalent).

& Never check or top up thebatteries with instruments usedfor lead-acid batteries

2. Precautions and practices

2.3. Electrical shocksand burns

Batteries assembled from a largenumber of monoblocks can attainhigh voltages. Therefore greatcare caution must be taken duringthe installation and maintenanceof a battery system to avoidserious burns or electrical shocks.

& Cut off the AC and DC circuitsbefore working on batteries.

Make sure that people understandthe risk of high voltage batteriesand that all manipulation iscarried out with insulated toolsand other adequate protectionequipment.

2.4. Possible dangersthrough hydrogen

Low maintenance STMmonoblocks are connected inhydraulic series. The hydrauliccircuit exhausts oxygen andhydrogen gases that areproduced during overcharge.

& The hydraulic system cancontain highly explosive gasesat any moment.

All interventions on the batteryrequire particular attention toprevent of any kind of leakage.If a leak is detected, it must berepaired immediately.Furthermore, general safety rulesmust be strictly observed:dispersion of gases as they leavethe hydraulic system to avoid theforming of dangerouslyconcentrated hydrogen gaspockets; and good ventilation.Keep the battery away from anyheat or ignition source.

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3.1. Assembly into batteries

The electrical connection in seriesof monoblocks will be madeaccording to the space availableand to minimize the length of thecables or rigid connections.

The connection of the hydraulicsystem to each of the monoblockswill follow a path parallel to theelectrical circuit so that there is no potential difference betweenthe two ends of a connectingpipe. The direction of the wateror gas flow is not important.

The maximum number ofmonoblocks connected in hydraulicseries is limited to 10 on a singlecircuit, which is equivalent to 50 cells. For larger battery units,several totally independent circuitsmust be provided (for details seechapter 3.3.).

During the installation intobatteries, the monoblocks must not be able to move in any threedirections depending on themechanical constraints.

The monoblock STM 5-140 MR’s are being shipped with belt plates.The monoblock STM 5-100 MR andSTM 5-100 MRE’s have built-in beltplates to prevent a swelling.

The plates of the monoblockSTM 5-140 MR’s can beremoved, under condition that the battery structure providessufficient protection againstdeformation of their small sides.

Only the small sides of the blocks must be braced in caseof connection of rows of several monoblocks.

In practice, the monoblock STM 5-140 MR’s will be set upin rows on the axis of the smallsides, without any gap but with a shim plate between themonoblocks. The consolidatedbracing system must withstand an expansion force of 150 daNper row.

Liquid-cooled STM 5-100 MREmonoblocks do not require freevertical space on any side.

By contrast, it is important toleave space between the largesides of the STM 5-100 MR andSTM 5-140 MR monoblocks inorder to ensure the collectivecooling through air circulation.The ventilation space betweenrows must be between 10 and 20 mm (refer chapter 3.2.).

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3. Installation

An installation according to the following, and perhapsmore specific, instructions isimperative to ensure thelongevity and performance ofthe battery as well as itsoperational safety. Specifically,the installation and assembly ofthe monoblocks into batteries,their hydraulic connection, andthe installation of the ventilationand cooling systems must bedone with great care.

For the final installation that willbe specific to every vehicle, this manual only providesgeneral guidelines.

All battery installations must be approved by Saft.

3.2. Ventilation and cooling

During operation (charge ordischarge), STM batteries generateheat, like all electrochemicalsystems. In daily use, a steady heataccumulation must be avoided.As a result, the battery needs agood cooling system in order todisperse the dissipated heatefficiently.

The free space of 10 mm to 20 mmbetween rows of STM 5-100 MRand STM 5-140 MR monoblockson their large sides serves as acooling corridor.

In addition, heat dissipationcan be improved by providingventilation space above and/orunderneath the STM 5-100 MRand STM 5-140 MR monoblocks.

In the case of forced air cooling,the ventilators will blow cold airvertically and horizontally acrossthe batteries. All cooling systemswill be dimensioned to ensure themost homogenous temperature ofthe monoblocks in one battery.

Furthermore, it is recommended tocontrol the battery temperature bysensors or thermostats, which canbe supplied by Saft on request.

The optimized solutions for acooling system must be designedfor every battery, depending onthe type of car, its use, the typeof battery etc.

& Special case of STM 5-100 MREliquid cooled monoblocks

Cooling of these monoblocks iseffected by circulation of liquid influid chambers on the large sides.

The basic design rules for a liquidcooling system are as follows:

- the maximum number of fluidchambers in a hydraulic series is limited to 3 with a pressureloss of < 80 mbar.

- in the best interest of thermalbalance, two fluid chambers thatbelong to one monoblock willbe connected through twoindependent cooling circuits.

- water flow of 40 l/h/series of 3 fluid chambers with amaximum pressure of 0.3 bar inthe hydraulic circuits must behomogenous. It must be assuredthat no preferential waterflowexists that would cause unevencooling of the monoblocks. When replenishing the coolingliquid, care should be taken thatno air bubbles form that wouldcause partial or no cooling at all,thus accelerating the agingprocess or the destruction of themonoblocks or the battery.

- the thermal exchange system ofthe cooling liquid/air is notincluded in the supplies fromSaft, except under specialcontract. This includes:distribution hoses, drainingaccessories, pump, radiator.

- during the mounting of thebattery and specifically duringthe installation of the electricand hydraulic circuits (filling andcooling), particular care must betaken that none of these threecircuits is interconnected.

- for details about the material anddimension of the hoses of thecooling system see appendix 7.

3.3. Assembly of centralizedwater filling system

3.3.1. Precautions andrecommendations

The centralized water fillingsystem links a number ofmonoblocks in hydraulic series.

The installation of such a systemmust therefore be effected with a maximum caution to avoid anyrisk of gas or electrolyte leakageto ensure good operationcompliant with required safetyregulations.

Important:

• To ensure that the hydraulicsystem is sealed, (no gas and/orwater leakages), the connectionof the ramp with hoses must bedone carefully. Whenever aleakage occurs (possible aftersome period of operation), itmust be repaired immediately.

• To minimize the risk of currentleaking into the hydraulicsystem (which is carrying gasesand water) verify the following:

- the hydraulic connection mustalways follow the electrical one,in order not to create a potentialdifference higher than thatbetween two cells at opposingends of the hose connection.

- the number of monoblocks that areconnected in hydraulic series islimited to 10 (50 cells maximum),which in turn limits the nominalvoltage of one ramp to 60 V.

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All Saft monoblocks to beequipped with a centralizedwater filling system, are equippedwith the water filling ramp.

All necessary accessories, such as hoses, pipes, elbows, can besupplied with each battery. List of part numbers, see app. 5.

3.3.2. General instructions for assembly

! Levels

The whole system should always beinstalled at the same level. However,if different levels exist, start thehydraulic circuit at the highest point,such that the water can always flowdownward and without causingmore pressure than that due to theloss of content in the ramps of themonoblock.

Install the water filling and gasoutlets in a well ventilated place,where the oxygen and hydrogengases can easily disperse andevacuate. All risks of sparks andignition sources must be avoided. It is imperative to protect theoutlets against rain, dust, mud, etc.

During the study of the pipelayout, attention should be giventhat no syphon containing wateror condensation can block theoutlets in case of freezing.

! Pipes and hoses

For the hydraulic connectionbetween two monoblocks, use ahose as specified in appendix 6.

For distances greater than 200 mm (between the batteryand the water tank for example),or to form a loop, use flexiblereinforced PVC pipe with adiameter of 10 x 16 mm, partnumber 208 859.

For very tight loops it is preferableto use a 90° polypropyleneelbow, part number 444 103.

Avoid any nipping or squeezing ofthe flexible pipes or hoses duringthe assembly of the system.

Avoid forming vertical loops inwhich water would remain after the filling operation.

! Inlets and outlets

During normal operation (nottopping-up), the hydraulic circuitmust be closed on one side (inlet),such that any gas can escapethrough the outlet on the other side.

! Water inlet

Use self closing connecting plugs,part number 280 604 (femaleconnector) and part number 280 605 (male connector). When disconnecting these plugs,both parts will automatically beclosed, i.e.

- the inlet to the hydraulic circuiton the battery side is closed,

- the pipe to the water reservoir isclosed, and stops the water flow.

! Water and gas outlet

Do not use self-closing plugs. Use free-pass plugs, part number280 602 (female connector) ordirectly the soft pipe in reinforcedPVC 10 x 6, part number 208 859.

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4.1. Procedure before use

a) Upon receipt, remove transportplugs from monoblocks, if any.

b) Ensure correct and sealhydraulic interconnections.

c) Verify that electrical inter-connection of the blocks and the connection of the battery tothe vehicle are correct.

d) Check tightness of terminalconnecting nuts.

• Torque applied should beas follows: 12 ± 2 N.m

4.2. Commissioning cycleand topping-up with water

a) Commissioning at constantcurrent charge (see table below).

b) Top-up with water, using thecentralized water filling system30 minutes after the end of thecharge.

4. Placing into service

13

Low maintenance STMmonoblocks are deliveredfilled and electricallydischarged. On receiptand/or after a storageperiod, a commissioningcycle is required.

Do not top-up with waterprior to the first charge, even if the electrolyte level isunderneath the minimum levelor does not show at all. After long storage periods,the electrolyte can be totallyabsorbed by the electrodes

Individually shippedmonoblocks or batteries areequipped with transport plugson the ramps or filling circuitsto avoid the loss of electrolyte

STM 5-100 STM 5-100 STM 5-140 MR MRE MR

Current (I) 7 A 10 A 9 A

Time (t) 21 h 15 h 22 h

Voltage (V) no limit *

* Voltage can reach 9 V per monoblock.

Maximum temperature at the beginning of the charge: + 35°C

Maximum temperature during the charge: + 50°C

Commissioning cycle of STM monoblocks

5.1. Operating temperature

Due to the electrochemicalreaction, all Ni-Cd batteriesgenerate heat during charge anddischarge. As STM monoblockbatteries are batteries of highenergy density, and they are used in regular cycling, particularattention must be paid to thetemperature of the battery. Daily use in electric vehiclesrequires the control of thetemperature and the installation of a cooling system to preventthe authorized maximumoperational temperature frombeing exceeded.

The temperature measured insidea central cell must always bebelow + 60°C.

! Temperature during charging

For optimum battery performanceand life, it is preferable to begincharging at an internal batterytemperature of below + 35°C.

This means, in practice, after adischarge, it is necessary to takeenough time to let the battery cooldown to below + 35°C beforestarting the charging operation.Charges at higher temperatureare always possible, but thebattery capacity and its useful lifewill progressively be reduced.Nevertheless, full capacity will berestored after some full charges attemperatures below + 35°C.

5.2. Two-level charge

5.2.1. Normal charge

In cycling applications, STMbatteries are preferably chargedat constant current between 0.15and 0.2 C5A.

5.2.2. Fast charge

It is possible to recharge up to80% with a current between 1and 1.5 C5A.

The fast charge current is appliedas follows:

• STM 5-100 MR-MRE: 150 A

• STM 5-140 MR: 210 A

5.2.3. Maintenance charge

This is a normal charge with ahigher overcharge coefficient thatwill permit increased capacity. At its term, the battery is topped-up with water.

5. Operation

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5.2.4. Recommended chargingmethod

For ambient temperature between0°C and +35°C.

& The charging method describedbelow is generally applicable forSTM MR-MRE batteries installed in electric vehicles. However,individual charging methodsmight be required for specificcustomer needs, depending onthe application, climaticconditions, etc. For exceptionalcases, consult Saft.

The recommended chargingmethod for Saft STM MR-MREbatteries is two-level constantcurrent charge IOla, as shown inthe diagram below.

! Principle

The battery is charged at constantcurrent. Its voltage increases. As soon as the predeterminedcharging voltage has beenreached, the charge current isreduced in order to limit uselessheat dissipation during

overcharge while assuring thenecessary overcharge. The change-point threshold, isindicated in the diagram by asmall circle.

First level: constant current at 0.2 C5A up to predeterminedthreshold voltage.

Second level: constant currentreduced to 0.05 C5A withoutvoltage limitation.

The charge coefficient is 1.15.

The maximum charging timeof a fully discharged battery isapproximately 8 hours.

! Temperature compensation

It is essential that the batteryreach the threshold voltagebefore it is fully charged. As thevoltage characteristics of Ni-Cdbatteries vary with theirtemperature (higher voltage whencold and lower voltage whenhot), it is imperative to correct thevoltage threshold according tothe battery temperature.

The relation between thresholdvoltage and temperature can beviewed as linear.

The voltage threshold for STMbatteries is indicated at atemperature of +10°C and isadjusted according to the batterytemperature with a negativecoefficient in millivolts per °C.

' Voltage thresholdThe voltage threshold that ends the first level is set at 1.63 V/cell, i.e. 8.15 Vper monoblock.

' Temperature coefficient:For T>10°C–0.003 V/°C/cell, i.e. –0.015 V/°C/monoblock.

For T<10°C–0.006 V/°C/cell, i.e. –0.03 V/°C/monoblock.

Cut-off can be manual,controlled by a time switch,or electronically.

15

0 0.05 0.2 end of chargeCharge condition (C5A)

Second level

Volta

ge (V

)

Volta

ge (V

) Cur

rent

(A)

Voltage

Set voltagethreshold

Current

Second level

First level

First level

Charge time

Examples of charge voltage at different temperatures:

! Charge of an STM monoblock at +35°C:Voltage threshold at +10°C ..............................................8.15 VCharge temperature ........................................................+35°C Temperature difference starting at +10°C ............................+ 25°CCorrecting factor of the:Voltage threshold +25°C x (–0.015) V/°C =.................. –0.375 VVoltage threshold for charge at +35°C 8.15 V –0.375 V = .. 7.78 V

! Charge of a STM monoblock at 0°C:Voltage threshold at +10°C ..............................................8.15 VCharge temperature ..............................................................0°CTemperature difference starting at +10°C ............................–10°CCorrecting factor of the:Voltage threshold –10°C x (–0.03)V/°C = ........................ +0.3 VVoltage threshold for charge at 0°C8.15 V +0.3 V = .......... 8.45 V

A special document concerning the charging methods recommended bySaft is available on request from the application service.

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STM 5-100 MR and MRE STM 5-140 MR

First levelConstant current 20 A 28 A0.2 C5AVoltage threshold 8.15 V/monoblock 8.15 V/monoblockTime t1 until the voltage threshold is reached

Second levelConstant current 5 A 7 A0.05 C5AVoltage threshold open open

Temperature –0.015 V/°C/monoblock T>10°Ccoefficient –0.03 V/°C/monoblock T<10°C

Overcharge 1.15coefficient

Recommended charge method for STM monoblocks

5.3. Discharge

5.3.1. Discharge current

The maximum current incontinuous discharge is 2 C5A.If necessary, the monoblocks mustbe cooled to limit heating(electrolyte temperature < +60°C).

Peak discharges of short duration,less than or equal to 10 sec, upto a current of 5 C5A arepermitted according to the stateof charge and the minimumacceptable voltage of themonoblocks.

5.3.2. Voltage in discharge

The voltage level duringdischarge depends on thecurrent drawn on the battery, and the temperature.

The rated capacity of STMmonoblocks is set at +20°Cfor an end voltage of 5 V.

In practice, STM monoblocks canbe very deeply discharged.Occasional polarity inversion willnot harm the monoblocks.

However, this polarity inversionmust remain exceptional to avoidwater consumption not taken intoaccount by topping-up.

The table on the right showsgeneral rules and voltages:

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STM 5-100 MR and MRE STM 5-140 MR

Constant 200 A 270 A

Peak (10 s) 500 A 680 A

Maximum discharge currents

Current Capacity measured at End voltagein operation

0.2 C5A 5.0 V/monoblock 4.9 V/monoblock

1 C5A 4.5 V/monoblock 4.4 V/monoblock

2 C5A 4.2 V/monoblock 4.0 V/monoblock

End voltages in discharge

6.1. Periodic maintenance

Under normal operatingconditions, when chargingrecommendations are respected,and correcting factors areapplied, low maintenance STMbatteries require no regularmaintenance apart from topping-up (see chapter 6.2.).

A brief overall inspection of thebattery system during a generalrevision of the vehicle should becarried out. The following pointsare to be verified:

• the state of the fans, if present,

• the tightness of the connections,

• the seal of the hydraulic circuit(filling, cooling),

• cleaning the batteries withsoapy water (detergents must be avoided).

The verification of the electrolytedensity is both unnecessary andimpossible.

6.2. Topping-up operation

! Measuring the electrolyte level

Topping-up with distilled ordemineralized water (for waterquality refer to chapter 2.2.) is necessary, because Ni-Cdbatteries consume water throughelectrolysis during overcharge.

The electrolyte level is visiblethrough the plastic container of the STM 5-100 MR monoblocksduring charge. The electrolytelevel is not visible in the STM 5-100 MRE monoblocks dueto the double walls of the fluidchambers, and barely visible in the STM 5-140 MR monoblocks. The only reliable time to measurethe electrolyte level is at the end of charge or a few minutes afterthe end of charge (when theelectrolyte is at its highest level).

In practice, topping-up is doneaccording to overchargedamperehours.

! Frequency of topping-up

After a number of cumulatedovercharged amperehoursaccording to model:

• STM 5-100 MR et MRE: 1 000 Ah overcharged

• STM 5-140 MR: 800 Ah overcharged

! Topping-up operation

& Topping-up must not be carriedout during the first 30 minutesafter the end of an overcharge(1), but it can be carried outduring a peak charge period and after its controlled term (2).

Water is filled into the hydraulicsystem from a reservoir by gravityor by vacuum, according to the principles described inchapter 1.4.

When topping-up is effected usinggravity, the flow rate at the inletmust be between 0.7 and1 liter/minute and the relativepressure at the inlet of the first cell of the first monoblock must be less than 0.15 bar relative.

Stop filling a few seconds afterwater spills over at the ventpipe(s). The inlet pipe will closeand the flow of water will stopautomatically when the inletconnector(s) are being removed.

When topping-up is effected usinggravity, the flow rate at the inletmust be between 0.7 and 1 liter/minute and the relativedepression in the monoblock mustbe less than or equal to 0.3 bar.

6. Maintenance

18

(1) During the first 30 minutes followingthe end of the overcharge, the residualgases from the overcharge process candisturb the filling operation and, mostimportantly, decrease the water quantityfilled into the cells.

(2) After the 30 minutes period followinga controlled term of the peak charge, theelectrolyte level is too low, such that themonoblocks will be overfilled, thusseriously risking an overspill of electrolyteduring the following charge andconsequently a dilution of the electrolyteduring the next topping-up.

7.1. Electrolyte specificdensity

Low maintenance STMmonoblocks equipped with acentralized filling ramp welded tothe cover can be considered asbeing closed. Measuring orreconcentrating the electrolytedensity is impossible.

However, if a concentration of the electrolyte is deemednecessary, this can only be doneby specialists from Saft.

7.2. Reconditioning

Reconditioning becomesnecessary when the batterycapacity is judged as being toolow, when the battery or theelectronics of an electric vehiclehave been repaired, or when ithas lost the battery managementinformation.

Procedure:

Commissioning charge at constantcurrent as described in chapter 4.2:

• STM 5-100 MR:7 A during 21 hours

• STM 5-100 MRE:10 A during 15 hours

• STM 5-140 MR:9 A during 22 hours

7. Equipment repair and overhaul of batteries

19

Appendix 1

20

Monoblock STM 5-100 MR + G RD equipped

Positive left – Filling right

21

Appendix 2

Monoblock STM 5-100 MRE + G RD equipped

Positive left – Filling right

Appendix 3

22

Monoblock STM 5-140 MR + G RD equipped

Positive left – Filling right

Appendix 4

23

Monoblock STM 5-140 MR + D RG equipped

Positive right – Filling left

Accessories for the centralized filling system

Reinforced soft PVC hose10 x 16 208 859 for connections > 200 mm

Polypropylene elbow 444 103 hose-to-hose connection

Female connector 280 604 plug, normally closed

Male connector 280 605 plug, normally closed

Female connector 280 602 free

Male connector 280 603 free

Male connector 280 804 free(wall penetration)

Male connector 280 805 self-closing(wall penetration)

Appendix 5

24

Basic specification for filling circuit hoses

Operating temperature: –30°C to +70°C

Maximum relative operating pressure: 300 mbar

Resistant to the following liquids:

• Electrolyte KOH (solution at 400 g/l) and NaOH (solution at 100 g/l)

• Oil 75 W 80

• Brake fluid

• Lead-free gasoline

• Cooling liquid

• Vaseline

Base material: Elastomer EPDM (“all rubber”, without internal reinforcement)

Resistivity: 106 Ω.cm, as per ASTM D257

Recommended dimensions for sleeveless connection to monoblock nozzle:• ∅ inside 9.4 ± 0.3• ∅ outside 14.1 ± 0.3

Visual: No color requirements specified

The inside of the hoses must be perfectly smooth to avoid leaks when fitting the hose onthe connecting nozzles.

Appendix 6

25

Basic specification for the cooling system hoses

Operating temperature: –30°C to +70°C

Maximum relative operating pressure: 500 mbar

Resistant to the following liquids:

• Electrolyte KOH (solution at 400 g/l)

• Oil 75 W 80

• Brake flluid

• Lead-free gasoline

• Cooling liquid

• Vaseline

Elasticity test: 4 000 cycles at +20°C, relative pressure: 0 – 500 mbar

After pressure cycle, verification of tightness at relative pressure of 300 mbar between –30°C and + 70°C

Base material: Elastomer EPDM (“all rubber”, without internal reinforcement)

Resistivity: 106 Ω.cm, as per ASTM D257

Recommended dimensions for sleeveless connection to monoblock nozzle:• ∅ inside 7

+ 0.2– 0.3

• ∅ outside 11.6 ± 0.5

Visual: No color requirements specified

The inside of the hoses must be perfectly smooth to avoid leaks when fitting the hose onthe connecting nozzles.

Appendix 7

26

Basic specification for rigid connections

Base material: baseline inspected annealed copper, as per chapter 4.2.1 of regulation NF A 51.119

Protection: nickel-plated, adhesion as per chapter 4.2 of regulation NF A 91.101

Recommended cross chapter: 40 mm2 16 x 2.5

Boring: ∅ 8.25 ± 0.2

Appendix 8

27

Basic specification for distilled or demineralized water

Physical characteristics

Limpid, colorless, odorless when boiling

Resistivity at +20°C > 30 000 Ω.cm

Chemical Characteristics

• 5 pH 7

• Absence of organic matter and reducing substances:

COD (chemical oxygen demand) < 30 mg/l (permanganate test)

• Total ions SO2– + CI–< 10 mg/l and CI– < 2 mg/l4

Dry residue 15 mg/l

Silicium as SiO2 < 20 mg/l

Appendix 9

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Industrial Battery Group12, rue Sadi Carnot - 93170 Bagnolet - France

Tél. : + 33 (0)1 49 93 19 18 • Fax : + 33 (0)1 49 93 19 50 • www.saftbatteries.com Doc N° RM 04.01 - 21085.2

Informations in this document is subject to change without notice and becomes contractual only after written confirmation by Saft

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