We can say that the high voltage battery is one of the most important component of a battery electric car.
The battery have a significant influence on a car components and different attributes of the vehicle, so like:
- max. traction motor torque;
- maximum regeneration;
- brake torque;
- vehicle range;
- total weight of the electric car;
- electric car price.
It is true that all major aspects of a pure electric car depend on the parameters of the high voltage battery. To do electric vehicle battery design we are going to start from core input parameters:
The main input parameters to do vehicle battery design:
An electric vehicle’s battery consists of several electrochemical cells. The main task of the battery is the conversion of chemical energy into electrical energy when discharged and, accordingly, electrical energy into chemical energy (when charged). The type of battery depends on the elements that are contained in it.
Battery design: 1) electrodes – anode and cathode; 2) separators; 3) Terminals; 4) Electrolyte; 5) Case.
The battery pack forms of modules that are interconnected. A module is a separate battery cell.
We are going to consider Lithium-ion cells, because is that Li-ion batteries have highest specific energy and specific power.
A high-voltage storage battery consists of battery cells arranged in chains and modules. The battery cell is the smallest voltage division.
Individual elements are grouped in parallel or sequentially in the form of modules. The number of module levels determines the characteristics of the battery. The number of cells corresponds to the total voltage of the battery. So the voltage of 6 series-connected cells will be equal to the sum of their individual voltage. To increase battery capacity, you need to connect more lines in parallel.
So, for example, a Mitsubishi i-MiEV high-voltage battery includes 22 modules, which consist of 88 elements connected in series (4 elements in each). Since each element has a voltage of 3.7 V, the total battery voltage is 326 V.