Abstract
ABSTRACT – As a rule, Li-ion battery packs for traction can handle much less charging power than they can deliver propulsion power. To be more energy-efficient and recover more energy, the objective is to develop a battery pack and battery management system (BMS) that allow for full regenerative braking at 0.5g and will be integrated in a fully electric sports utility vehicle (SUV). The hardware of the BMS has been developed by a partner company, the software is programmed internally on a Linux embedded OS. The BMS software has a master-slave architecture. Care has been taken to make the software as modular as possible so that all BMS boards can be configured as slave or master or even both. Two equal battery packs have been built using LTO-type Li-ion cells, which were chosen because they can handle high regenerative currents and are very safe. A lightweight-concept battery pack casing has been developed on the basis of prototype modules, each of these modules having been equipped with a different cooling concept. The final battery pack and its Peltier cooling system have been tested in thermal tests in a climate chamber together with a programmable load. These tests have been conducted on this battery and on other packs to compare their behaviour under a typical battery electric vehicle (BEV) load. The full battery pack was also subjected to electromagnetic interference (EMI) tests. Result: the battery pack continues to operate within specifications under a continuous nominal load of 50 A at an elevated room temperature of 40°C, meaning that the cell temperatures stay below 45°C and the distribution of these cell temperatures is less than 5°C. The EMI tests were passed after having optimised the shielding. Battery pack and battery management system are integrated in a functional demonstrator, i.e. an all-electric Range Rover Evoque.
KEYWORDS – battery management system, regenerative braking, electric vehicle