Battery Management System Reference Design

ID 683279
Date 4/02/2016
Document Table of Contents

1.3.1. BMS Reference Design Car Model

The car model computes the electric power at the battery’s terminals, so that the vehicle speed follows a driving cycle. You can select from 11 standard driving cycles.

The Urban Dynamometer Driving Schedule (UDDS), the Highway Fuel Economy Test (HWFET) and the Federal Test Procedure (FTP) are defined by the U.S. Environmental Protection Agency. The New European Driving Cycle (NEDC), the Extra-Urban Driving Cycle (EUDC) and the Economic Commission for Europe urban driving cycle (ECE R15) are maintained by the United Nations Economic Commission for Europe (UNECE). The Common Artemis Driving Cycles consists of the Urban cycle (ArtUrban), the Rural road cycle (ArtRoad) and the Motorway cycles (ArtMw130 and ArtMw150, with a maximum speed of 130 and 150 km/h, respectively). The Worldwide harmonized Light vehicles Test Procedures (WLTP) Class 3 is developed the following the guidelines of UNECE World Forum for Harmonization of Vehicle Regulations. The various cycles differ in the average speed and electric power required from the traction battery.

Table 1.  Driving Cycle DetailsThe duration, Distance and average speed of each cycle
Driving Cycle Duration (min) Distance (km) Average speed (km/h)
UDDS 23 12.0 31.5
HWFET 13 16.5 77.5
FTP 31 17.8 34.1
EUDC 7 6.5 58.6
NEDC 20 8.3 25.4
ECE R15 3 0.9 16.5
WLTP class 3 30 23.2 46.5
ArtUrban 17 4.9 17.6
ArtRoad 18 17.3 57.4
ArtMw130 18 28.7 96.8
ArtMw150 18 29.5 99.5
The reference design implements a dynamic model to simulate the behaviour of a car. You calculate the mechanical power Pm as the sum of three contributions: one linked to the acceleration, one because of the air resistance and another because of the rolling resistance:
Figure 11. Car Model Equation


  • M is the kerb weight
  • S is the frontal area
  • C X is the drag coefficient
  • R is the rolling resistance
  • ρ air is the air density
  • g is the gravity acceleration
  • v is the speed.

You obtain the electric power P e from P m where:

  • η wheel is the efficiency from the battery to the wheels
  • η reg is the efficiency in the opposite direction, i.e., during the regenerative breaking.

To obtain the battery current, divide the electric power by the sum of the cell voltages calculated by the battery model.