The paper shows a battery module for the latest model. It adopts a metal casing to reduce the size while it maintains the same output as a conventional model. Its power density is improved by 30% achieving the world's top level. In the 2003 model, modifying the cell interconnection reduced the internal electrical resistance. Additionally, since the cells operate independently in the new model they can be combined and arranged freely. The latest model features 8 cells in series connected. The battery pack is shown, as well as its wiring diagram. Electrical equipments such as battery monitoring unit, current sensor, relay (SMR), junction box, service plug, and wire harness are incorporated in the battery pack. They have isolation and fail-safe function, the battery pack is designed to protect driver and passengers, and service staff from contacting voltaged parts. Battery pack cannot be opened without removing a service plug. Each electrical equipments will describe in the following section. In a previous hybrid model, 'battery monitoring unit' was measuring the voltage, current, temperature, state of charge (SOC), and to control cooling system. In 2005 model, function rearrangement is made so HV ECU can have SOC monitoring and cooling control function. Battery monitoring unit now has only a sensor function. In result, the size, weight, and cost were reduced. Conventionally, 'the resistance voltage dividing method was used to detect the voltage of hybrid battery. Although this method could detect the voltage of many batteries connected in series at a short time, it required an exclusive power supply unit and isolation element, which resulted in substantial volume. 'Flying capacitor method' was applied to the new monitoring unit having a photo MOS relay at the input circuit of voltage detection. It does not require a conventional isolation power supply because photo MOS relay itself has isolation character and a switching circuit. General measuring instruments uses single flying capacitor method. The new monitoring unit uses 'Double flying capacitor method' using two flying capacitors instead. The benefits are as declared. With downsized electrical equipments and reduced number of parts used, the electric equipment volume of a battery pack was reduced 40%. Now, the downsized battery pack can be installed in the following location, in a luggage space, under the second row seat, between a driver and a navigator seat, without sacrificing the utility and the comfort of passengers. For these reasons the hybrid system can be applied to many types of vehicles such as SUV, sedan and mini-van.
Development of electric equipment for hybrid vehicle's battery
Entwicklung der elektrischen Ausrüstung für das Batteriesystem im Hybridfahrzeug
2007
7 Seiten, 12 Bilder, 1 Tabelle
Aufsatz (Konferenz)
Englisch
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