Technical handbook installation, operation and …

1 Technical handbookinstallation, operation and maintenance of air cooledNi-Cd block units type STM recommendations51. Characteristics of STM General description operation principle of vented Ni-Cd cells Description of STM nickel-cadmium blocks Mechanical characteristics Electrical characteristics Water filling system General description Working principle of the vent plug 92. Precautions and Transport, storage Water and electrolyte Water quality Harm caused in using sulfuric acid Electrical shock and burns Possible dangers through hydrogen 113. Installation12 Assembly into batteries Ventilation and cooling Assembly of water filling system Precautions and general rules General instructions for assembly Fitting the elbow on the plug 13 Contents 4.

2 Placing blocks into Preparation before use Commissioning cycle 155. Operating temperature Charging in service Constant current charge Recommanded charging method Discharge currents End voltages in discharge 186. Periodic maintenance Topping up operation 197. Equipment repair and Electrolyte specific gravity Reconditioning Replacing vent plug 21 Appendix 1 22 Appendix 223 Appendix 3 24 Accessories of the water filling system 25 Edition April 2001 Introduction4 The information provided in thismanual is intended to help operatorand maintenance personnel toobtain the best performance andmaximum life from their Saft Ni-CdSTM block describes the main characteristicsand operating principles of theblocks and provides generalinstructions to users and technicianson how to operate, maintain, repair, overhaul and otherwise care for instructions are of generalvalidity for batteries in ElectricVehicles.

3 Nevertheless, every type of car will have a specific batteryassembly and particular operatingprinciples, especially with regards to the various mechanical, electrical,thermal and other instructions depending onthe type of car can therefore beadded to this you wish to use the battery outsidethe limits stated herein, pleaseconsult us recommendations5!Install the battery such as toensure good ventilation.!Never allow a flame or fire tocome near the battery. !The electrolyte is harmful toskin and to eyes in the event of contact with skin or eyes, wash immediatelywith running water and/or a 10 % solution of boric acid.!Wear gloves and goggles tomanipulate the electrolyte.!Never use sulfuric acid oracidified water to top-upelectrolyte, as acid, even intraces, destroys the battery.

4 !When batteries are operated in closed premises, room airshould be renewed inaccordance with applicablesafety codes and Characteristics of STM General description operation principle ofvented Ni-Cd cells Batteries are electrochemicaldevices used to supply energy toelectrical and electronic energy stored in abattery is converted into electriccurrent when the battery isdischarged. This electric current is produced directly by chemicalreactions that occur within the 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 are highlyinsoluble in alkaline remain as solids and do not dissolve while undergoingchanges in oxido-reduction of this, the electrodesare long-lived, since no chemicalmechanism exists that wouldcause the loss of active materials.

5 During the cell charging anddischarging operations , hydroxylions are transferred from thepositive to the negative plates via the electrolyte. The alkalinesolution, KOH, (electrolyte) actsonly as the transfer medium. It does not participate in theelectrochemical reaction. Its rolein the operations being ratherpassive, the electrolyte in anickel-cadmium cell is neveraffected by the state of charge of the cell itself. During overcharge, the watercontained in the electrolyte isdecomposed into O2and H2. A part of these gasses leaves thecells through their vents and thehydraulic system. Consequently,the electrolyte reserve is reducedand topping up of the cells withwater becomes necessary after a certain number of cycles.

6 Description of STM nickel-cadmium blocks STM blocks consist of 5 nickel-cadmium cells of V nominalvoltage each. Assembled into acompact unit of 5 cells, the STMmonoblock has a nominal voltageof 6 V. If delivered in single block units(not pre-assembled by Saft intocrates or boxes), the blocks aresupplied with end plates. Do not remove those of the STM blocks, as they areintegrated into the block container. The blocks will be assembled intoa battery by serial (and eventuallyalso parallel) interconnection, inorder to achieve the specifiedbattery capacity and mounted into a vehicle, the blocks must be installed withsufficient space for ventilation(refer to chapter 3). !ElectrodesThe STM blocks are constituted of sintered positive electrodesand plastic bonded negativeelectrodes.

7 The sinter positive is obtained by chemicalimpregnation of nickel hydroxideinto a porous nickel structure,which was obtained beforehandby sintering nickel powder onto a thin, perforated and nickel-plated steel strip. Positive andnegative electrodes are organisedin alternates and separated by a multi-layer separator. !ElectrolyteThe alkaline electrolyte in a nickel-cadmium battery is a solution of potassium hydroxide(KOH), lithium hydroxide (LiOH),sodium hydroxide (NaOH) anddistilled or demineralized the electrochemicalreaction, its specific gravityremains essentially constant andcan thus not be used as anindicator of state of charge. The specific gravity, however,varies due to the normal waterconsumption during gravity is low when the cellsare topped up to their maximum,it is high when the electrolytereserve is all consumed.

8 The electrolyte used in STM blockshas a specific gravity of !Block containerThe block container is made oftranslucent polypropylene. The block cover, also inpolypropylene, is thermoweldedto the container after introductionand interconnection of the plategroups ("through-the-wall"interconnection principle). Mechanical characteristics of STM 5-180 with end plates Length (mm): 260 Weight (kg): Width (mm): 190 Electrolyte reserve (cm3): 210 Height (mm): 260 Pole bolts: M 10 x drawings in appendix Electrical characteristics IEC rated capacity C5at C5A: 180 Ah Nominal voltage Un: 6 V Internal resistance R (fully charged) at + 20 C: 2 m Figure 1: Monoblock Water filling system General description This chapter describes theworking principle of the Saftsingle point water filling systemused on STM blocks.

9 !Assembly instructions (see chapter ). !Using instructions (topping-up) (see chapter ). The water filling system links a number of blocks in normal operation of thebattery, the gasses produced inthe battery are exhausted throughthis hydraulic system. When topping-up of the battery isnecessary, water will be providedinto the system by gravity or by a pump and fill up cell by cell toa predetermined level. The filling of one hydraulic circuitis terminated when all the cells arefilled and the water comes out atthe end of the hydraulic circuit. The main component of the systemis the water filling plug (vent) whichensures both, the exhaust of gassesand the automatic regulation of theelectrolyte level during topping-up.

10 Maximum water flow: litre/minute can be filled either by gravity or pumpingDisposal or recycling to thewater tank either by gravityor by pumpingmax 10 blocks in hydraulic seriesFigure 2: Water filling system skeleton diagrammax meter (60 inches)Water filling ventDistilled water tankWater top, open only during water Working principle of thevent plug The concept is to fill a cell withwater up to a specified level (N)allowing gas which is in the cellto escape. When the specifiedlevel is reached, the electrolytecloses the gas exhaust tube andthe consequent excess pressurestops the water flow into the water will now flow to the next cell and so on, to the lastcell of the hydraulic circuit.