Battery life estimated by the results of the charge/discharge durability test and unused-deterioration durability test according to the cycle similar to urban distribution operation is indicated in Figure 15.
The deterioration curve of the lithium ion battery is linear and rather mild unlike the nickel hydrogen battery, which deteriorates rapidly. The deterioration from leaving the battery unused (not on duty) is equivalent to the deterioration from charge and discharge cycles (on duty). It is confirmed that the lithium ion battery has an equivalent service life to the vehicle itself.

Fig. 15 Durability of the Lithium Ion Battery

The Elf hybrid system is designed for sufficient durability and reliability; however, if the hybrid system should fail, the vehicle can be driven to the service shop with the diesel engine by isolating the hybrid system. Disengaging the dog clutch of the PTO and mechanically disconnecting the motor generator from the drive system isolate the hybrid system. The hybrid controller shuts off the high voltage system and the control system is disconnected from the vehicle. On the other hand, the engine controller provides normal control of the engine, and the controller for the Smoother-E Autoshift automatically changes the control map, etc., to that of a normal diesel engine vehicle in order to continue to drive the vehicle. When the function of the hybrid controller is completely lost, the vehicle is in a similar in limp mode.

Because there are no applicable high voltage safety standards for hybrid electric vehicles in Japan, engineering of the vehicle requires referencing the requirements for electrical shock protection in ECE-R-100 (Safety Requirements of the Electric Vehicle), which is under study in harmonization of ECE standards. Cables in bright orange color are used for high voltage circuits, and it is completely insulated from the chassis frame. The hybrid unit box is constructed with an enclosure function according to structural requirements so that the user cannot touch it directly. Safety against current leakage is enhanced by the installation of a leak detector and by connecting the frame and hybrid unit box with the bonding wire for potential equalization. By using a long life lithium-ion battery, the high voltage section is maintenance-free, and the risk of electrical shock during inspection is eliminated.