Battery System, Hybrid Drive: Description and Operation
1. Description of battery system design1.1 High Voltage Battery holder
The battery system contains one battery holder and the BECM (Battery Energy Control Module).
The battery holder contains 240 cells which are connected in series by the bus bar.
One battery module is defined as 4 battery cells.
One battery block is defined as two modules.
The battery holder contains 30 blocks (V1,...V30).
The voltage is measured from each block / double block to the battery ground potential (HV-GND).
The battery contains 16 block voltage sensors and two pack voltage sensors.
The battery current is measured next to battery potential line and the fuse.
The battery contains eight temperature sensors in the battery box, one inlet air and one outlet air temperature sensor.
The battery cooling is done by two fans.
1.2 Contactors
A contactor is a switch that connects the high voltage battery to the vehicle high voltage harness. There are three contactor which can be separately controlled:
positive contactor / precharge contactor
negative connector
1.3 Battery Energy Control Module(BECM)
The BECM contains a main-CPU and a sub-CPU.
The main functions of Main-CPU are:
- to establish the communication with the vehicle side (CAN)
- to control the contactors
- to control the fans
- to measure the battery temperature
- to calculate of the state of charge (SOC)
- to monitor the battery system
The main functions of the Sub-CPU are:
- to measure all voltages
- Pack Voltage
- Contactor Voltage
- Block Voltage
- to measure the battery current
1.4 States of the BECM
The following figure shows the states and transitions of the internal BECM state machine:
