Panasonic Corporation’s NiMH 12V Energy Recovery Systems is being applied in the new idle-stop (stop-start) minicars just introduced by Nissan Motor and Mitsubishi Motors in Japan: the Nissan DAYZ ROOX and Mitsubishi eK Space. The new models were designed and developed for the Japanese market by NMKV Co., Ltd., a joint venture formed by the two automakers.

The 12V Energy Recovery System, which is designed to be connected in parallel with the main lead-acid battery, is based on new D-size nickel metal hydride (NiMH) battery cells. The main lead-acid battery is often placed in the engine compartment. As the new energy recovery system can be installed in the same compartment, it is possible to reduce cable connection resistance and simplify wiring.

To enable such a setup, Panasonic developed battery cells that can endure the high-temperatures of the engine compartment. Using technology acquired in developing HEV batteries, Panasonic has improved the battery design, such as the polar plates, electrolyte and other battery parts to increase charging efficiency and improve durability in high temperature environments.

The system has the same 12V voltage as the main lead-acid battery; as a result, the system eliminates the need for voltage transformation and enables simplification of the control and cooling systems.

Panasonic’s Ni-MH batteries are durable and able to maintain a high charging/discharging capacity over an extended period of time. This is supported by the company’s unique battery manufacturing technologies, including polar plate sintering technology, which involves the firing of metal nickel powder at high temperatures for manufacturing rigid, porous nickel substrate.

The 6Ah, 12V system uses 10 D-size NiMH cells; it measures 230 x 205 x 80mm and weighs approximately 3.4 kg (7.5 lbs).