MAIN BATTERY AND CELL MONITORING UNIT (CMU)



MAIN BATTERY



The main battery consists of lithium ion battery that is small and lightweight and also has a high energy density. The motor (electric motor unit) and the air conditioning system are powered by the main battery. The main battery is in the glass-reinforced plastic case that has high water-resistant properties, vibration-resistant properties, dust-resistant properties and high heat-resistant properties. The case is placed under the floor. The battery consists of two kind of modules, 8-cell modules in which 8 battery cells are in series, and 4-cell modules in which 4 battery cells are in series. 10 of 8-cell modules and 2 of 4-cell modules are used. In total, the 88 battery cells are connected in series, which produces the total voltage as 330 V.

CHARACTERISTICS OF MAIN BATTERY AND PRECAUTIONS IN USE


<Characteristics>
  • The main battery, which is based on lithium ion battery, can be charged before the stored energy is used up.
  • The main battery capacity gradually decreases with the lapse of time, depending on the operating/stored conditions.
  • The main battery performance can be varied with ambient temperature. Especially in the lower temperature, the cruising range may become shorter and the required time for charging may also become longer.
  • If the vehicle is stored in extremely high or low temperature, the battery capacity may decrease rapidly.
  • Even if the vehicle is not in use, the main battery may be gradually discharged and the energy stored in the main battery will be reduced.
<Precautions in use>
  • Storage of the vehicle for a long time with zero state on the energy level gauge would make it infeasible to charge the main battery due to the over-discharge and in some cases the main battery needs to be replaced.
  • When the vehicle is parked for a long time without use, charge the main battery fully every 3 months to avoid the over-discharge.

CELL MONITORING UNIT (CMU)


The cell monitoring unit (CMU) is mounted in each module. The battery cell voltage sensor measuring the voltage of each battery cell and the module temperature sensor measuring the temperature of the module cell are mounted in the module. There are three module temperature sensors where four battery cells are connected in series and six module temperature sensors where eight battery cells are connected in series. The signal is input into the CMU. This allows the CMU to monitor each cell conditions. The CMU has the balancer that smooths voltage variations among the battery cells.

SERVICE PLUG



The service plug is placed under the driver seat <L.H. drive vehicles> or under the passenger seat <R.H. drive vehicles>. Remove the service plug before performing the check and the maintenance work on the high voltage components to ensure the job safety, shutting off the high voltage circuit. Inserting and pulling the service plug switch installed to the main battery turns ON/OFF the service plug lever.

SERVICE PLUG SWITCH


The service plug switch is installed to the main battery. This switch detects the status of opening and closing a high voltage circuit on the service plug. The switch uses the service plug lever terminal to detect the status of inserting and pulling the service plug. Installing the service plug allows electricity to go through the service plug switch (interlock circuit) to input the ON signal to the EV-ECU. Removing the service plug allows electricity not to go through the service plug switch (interlock circuit) to input the OFF signal to the EV-ECU.