What is an Electric Vehicle Battery System?

What is an Electric Vehicle (traction) battery?
 

• A battery that stores chemical energy and then discharges it by converting the chemical energy into electric energy.  It is used to power the electric motors of the battery electric vehicle (BEV) or hybrid electric vehicle (HEV). 
  
• The batteries used are usually rechargeable batteries and use a lithium ion chemistry.  These batteries are specifically designed for high ampere – hour (kilowatt -hour) capacity. 

 
Example: Nissan Leaf 24 kW Electric Vehicle
 
The Nissan Leaf 24 kW Electric Vehicle battery contains:
 

•  48 modules
  
• each with 4 pouches = cells containing anode & cathode          = 192 cells in total 24 kWh LEAF battery.

 
Each module = nominal voltage of 7.5V
 

• battery pack has a nominal voltage of 360V (= 48 x 7.5V)

 
 
What is a Battery Management System, (BMS)?
 

• Most traction batteries are looked after by a device called a Battery Management System, (BMS).
  
• The purpose of the (BMS) is to protect the battery. 

How?
 

• The (BMS) looks at the state of charge and the operating data from each cell in the battery pack.
  
• If any cell is going to overcharge, over-discharge, or is overheating then the BMS will shut down the battery. 
• It will also do this if it senses any faults within the battery cells..