Battery operating conditions dependence

The practical full state-of-charge is the state-of-charge, which can be reached in a system under normal operating conditions (depending on the charge voltage, the maximum charge current and the short-time history of the battery). 

The data presented above depend on the operating conditions - especially the power levels (maximirm crrrrent) and the temperatiue. From the data in Table 4.1, it is clear that the supercapacitor is the best device for electrical energy storage in the transierrt state. It can be used for peak power demands for periods between a few seconds and several tens of seconds. It should be noted that the maximum number of charge/discharge cycles for a supercapacitor is around 500 times greater than the same statistic for a battery. Firrthermore, the supercapacitor can supply or absorb a... 

Battery chargers are employed for charging starter, traction, and stationary batteries as well as for supplying stand-by power. The demands for these devices are dependent on the operation conditions. 

Life and Failure Modes. The life of SLI batteries is affected by the design, the processing, and the operational environment of the battery. Because of the automated assembly methods used today, SLI batteries are fairly consistent in life under ideal operating conditions, but the wide variety of operating conditions tends to spread the failure distribution. Warranty coverage for a failed battery is often more dependent on marketing strategy than on the statistical expectations of the failure rate. 

The selection of a separator depends on the battery, but some general criteria that need to be considered include electronic properties, mechanical stability, chemical resistance, and electrolyte wettability. Most separators need to be good electronic insulators and should exhibit minimal electrolyte resistance. They should have excellent mechanical and dimensional stability adequate for operations as well as for easy handling. The separators need to be chemically inert under the harsh conditions of battery operation and should be effective in preventing migration of particles between electrodes. We shall discuss the specific properties of separators for a specific type of battery later in this chapter. 

Once in an operational battery, the separator should be physically and chemically stable to the electrochemical environment inside the cell. The separator should prevent migration of particles between electrodes, so the effective pore size should be less than 1pm. Typically, a Li-ion battery might be used at a C rate, which corresponds to 1-3 mAcm2, depending on electrode area the electrical resistivity of the separator should not limit battery performance under any conditions. 

Apart from hydrocarbons and gasoline, other possible fuels include hydrazine, ammonia, and methanol, to mention just a few. Fuel cells powered by direct conversion of liquid methanol have promise as a possible alternative to batteries for portable electronic devices (cf. below). These considerations already indicate that fuel cells are not stand-alone devices, but need many supporting accessories, which consume current produced by the cell and thus lower the overall electrical efficiencies. The schematic of the major components of a so-called fuel cell system is shown in Figure 22. Fuel cell systems require sophisticated control systems to provide accurate metering of the fuel and air and to exhaust the reaction products. Important operational factors include stoichiometry of the reactants, pressure balance across the separator membrane, and freedom from impurities that shorten life (i.e., poison the catalysts). Depending on the application, a power-conditioning unit may be added to convert the direct current from the fuel cell into alternating current. 

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