Energy Company of the Panasonic Group delivered a lecture on its energy recovery system that uses a nickel-metal-hydride (NiMH) battery and is targeted at no-idling vehicles at AABC 2013, which took place from Feb 4 to 8, 2013, in Pasadena, the US.
The title of the lecture was "12V Energy Recovery System with Nickel Metal Hydride Battery." In the lecture, the company showed that the market for no-idling vehicles is forecast to expand from about 1.1 million units in 2012 to about 48 million units in 2020 and that the sales of the newly-developed energy recovery system is expected to grow.
The system is used by combining a lead-acid battery, which is commonly used for energy recovery systems, and a NiMH battery. As a result, it became possible to improve fuel efficiency by storing the energy generated by reducing speed in the NiMH battery and reusing it. Also, the load on the lead-acid battery is reduced, extending the life of the battery.
The company expects that the system will further improve fuel efficiency in the future by supplying electricity not only to in-vehicle electric components but also to a starter motor that helps drive the vehicle.
The new system can be used just by connecting it to a lead-acid battery in parallel, and it does not require a DC/DC converter. Furthermore, because the company developed a cell that has excellent high-temperature properties for no-idling vehicles, the system can be installed in an engine room. Existing energy recovery systems using a lithium-ion (Li-ion) battery are placed in the car's interior because of their temperature properties.
The basic components of the system are 10 D-size cylindrical cells connected in series. The charging/discharging voltages of a system that has 10 NiMH batteries connected in series match those of a lead-acid battery in a wide SOC (state of charge) range, the company said, showing that the new system is superior to existing electric double layer capacitors and systems using lithium titanate (LTO) for negative electrodes.
The cell has the same shape as the one that the company mass-produces for hybrid vehicles. It enhanced high-temperature properties mainly by making improvements to electrolyte so that the system can be used at a temperature of 75°C, which is an operating temperature of a lead-acid battery. The charging efficiency of the cell for hybrid vehicles drastically lowers at a temperature higher than 60°C.
The Panasonic Group aims to apply the system not only to no-idling vehicles but also to auxiliary power supplies for shift-by-wire and steer-by-wire systems.