IEC 62973-2-2020 Railway applications – Rolling stock – Batteries for auxiliary power supply systems – Part 2: Nickel Cadmium (NiCd) batteries

IEC 62973-2-2020 Railway applications – Rolling stock – Batteries for auxiliary power supply systems – Part 2: Nickel Cadmium (NiCd) batteries. The plate stacks are surrounded by alkaline electrolyte, an aqueous solution mainly of potassium hydroxide (KOH)， and distilled or deionized water. The electrolyte does not participate in the electrochemical reaction, which takes place in the cell, but only acts as an ion-carrying medium with its specific gravity remaining fairly constant allowing for large electrolyte reserves to be used. The electrolyte does not chemically change or degrade due to charge/ discharge cycles. Due to NiCd electrochemistry technology, some abuse conditions can be tolerated at the cell level, e.g. overcharging will cause water electrolysis, but only water is consumed. Since there is no chemical change or degradation of electrolyte, it is not necessary to add complex control systems to handle such cases. 4.2.2 Sintered/PBE plate/electrode technology The sintered positive plate/ electrode is obtained by chemical impregnation of nickel hydroxide into a porous nickel sinter coated thin steel strip that is previously perforated and nickel-plated. The negative plastic bonded electrode (PBE) is obtained by the coating of slurry consisting of cadmium oxide mixed with a plastic binder onto a nickel-plated thin perforated steel strip. 4.2.3 Sintered/sintered plate/electrode technology The sintered positive and negative plate/electrode is obtained by chemical impregnation of nickel hydroxide and cadmium oxide into a porous nickel sinter coated thin steel strip that is previously perforated and nickel-plated. 4.2.4 Fiber plate/electrode technology Both the positive and negative plates/electrodes consist of non-woven fibers of nickel or nickel-plated plastic fibers of high porosity. 4.2.5 Pocket plate/electrode technology Both the positive and negative plates/electrodes consist of several flat, perforated metal pockets made from perforated steel strips linked together encapsulating the active materials. 4.3 Environmental conditions NiCd cells/ batteries can perform at extreme temperatures: below -25。C or above +40 °C. Especially when at one extreme temperature is specified, deviations for the opposite extreme temperature may be agreed between end user and/ or system integrator and cell/ battery manufacturer. 4.4 System requirements 4.4.1 System voltage The charging voltage for the NiCd battery is dependent on the number of cells, temperature, and its plate/electrode technology. Although the nominal battery voltage is set by Table 1 of IEC 62973- 1:2018, the number of cells can vary due to the cell charging requirements by their plate/electrode technology. Due to higher cell charging voltage required by the fiber or...