Hitachi Ltd announced Sept 17, 2008, that it developed technologies to increase the capacity of Li-ion rechargeable battery systems for diesel hybrid locomotives in collaboration with Hitachi Vehicle Energy Ltd.

The technologies will realize the hybrid version of high-speed diesel locomotives that run at 200km/h in the future, the companies said.

According to Hitachi, there are more than 100,000 units of diesel cars running in railroads all over the world. Recently, needs for reducing diesel vehicles' consumption energy and CO2 emissions are increasing due to, for example, soaring crude oil prices and global warming.

Hitachi and East Japan Railway Co jointly developed a series diesel hybrid drive system. And, in July 2007, East Japan Railway started the operation of the Ki-Ha E200 diesel train equipped with this system on the Koumi Line in Yamanashi Prefecture, Japan, as the test car prior to the mass-production.

Based on the system used for the Ki-Ha E200, Hitachi increased the number of Li-ion rechargeable batteries used in the new system by improving the cooling performance of the battery module and the performance of the controller circuit that monitors and controls the performance of many batteries. The Li-ion battery itself is the same as that used in the Ki-Ha E200.

An electricity storage system for a diesel hybrid locomotive has many batteries (cells) connected in series and in parallel. Thus, it is faced with a problem of how to operate the controller properly when the voltage increases due to a growing number of battery series.

Hitachi provided a series controller that only monitors the cells connected in series, in addition to controllers that monitor individual cells and a higher controller that performs the centralized control of lower controllers to reduce the load on the higher controller.

Furthermore, each of the controllers is composed of multiple substrates, and only the transmission between the adjacent substrates is permitted, thereby reducing the insulation voltage of individual substrates. The controller LSI is the same as that used in the existing system.

The adoption of these technologies realized an electricity storage system with a 1,500V-class voltage and a capacity of up to 300kWh. (The battery capacity of the Ki-Ha E200 on the Koumi Line is 15.2kWh.) The market for such storage systems is not very big in Japan, but the system is applicable to diesel hybrid locomotives, which can replace the high-speed diesel locomotives currently operating in Europe and developing countries.

A diesel hybrid locomotive can improve the fuel efficiency by about 10-20%. It also reduces the emission of particulate matter (PM) and NOx because the diesel engine can be driven at an optimum engine speed. Furthermore, it has a merit of low noise because it runs on the motor alone at startup.

Hitachi's new system is scheduled for display at "InnoTrans 2008," an exhibition of railway technologies, which runs from Sept 23, 2008, at Berlin Messe in Germany.