Nissan minicars to feature Panasonic 12V NiMH regenerative systems
The Nissan DAYZ ROOX (pictured) will feature a new 12 volt system developed by Panasonic using nickel metal hydride (NiMH) batteries to quickly store energy recovered from braking/stopping. This energy can be used to power the car's accessories and systems during idle stop, similar to the auto stop-start mild hybrid option in some other cars, but with a more aggressive nature.
The 12V system utilizes D-size NiMH battery cells that work in parallel to the standard lead-acid battery the car normally has for powering accessories and on-board systems. The new batteries are placed very near the standard battery to simplify connections and reduce resistance losses. Part of Panasonic's work was building NiMH batteries that can withstand the high temperatures of an operating engine compartment as well as to improve the charging efficiency and durability of the batteries.
The system has the same voltage as the lead-acid battery and the car's components, allowing it to tie in directly without losses from conversions. Panasonic chose NiMH for its long-term durability and lengthy lifespan. Panasonic uses a special manufacturing process for polar plate sintering which involves the firing of metal nickel powder at high temperatures to make a more rigid, porous nickel substrate.
The total system comprises ten of these D-sized NiMH cells and measures only 230x205x80mm with a total weight of just 7.5 pounds. It allows the Nissan DAYZ ROOX (and its Mitsubishi counterpart, designed in collaboration, the eK Space) to recover energy from braking, store it in the NiMH batteries, and use that energy to power electrical components in the car while stopped, letting the system shut off the engine to conserve fuel. Because the systems run from the Panasonic batteries instead of the main lead-acid battery, the engine can start easily from the main battery and reduce battery wear as well as risk of battery drain. Further, the NiMH batteries allow longer-term storage of power recovered.