Possibilities to identify defective electric automobile batteries

D. Berjoza¹, V. Pirs¹ and I. Jurgena²

¹Latvia University of Life Sciences and Technologies, Faculty of Engineering,
Motor Vehicle Institute, J. Cakstes 5, LV–3001 Jelgava, Latvia
²Latvia University of Life Sciences and Technologies, Faculty of Economics and Social
Development, Institute of Business and Management Science, Svetes street 18,
LV–3001 Jelgava, Latvia
*Correspondence: dainis.berjoza@llu.lv; inara.jurgena@llu.lv

Abstract:

A pack of batteries is one of the most important and expensive assemblies for an electric vehicle. A pack of batteries is comprised of several batteries connected in series. The number of the batteries connected depends on the operating voltage of the vehicle’s on-board system as well as on the individual characteristics of the batteries used, e.g. the operating voltage of a single cell. One or several cells of a pack of batteries could be damaged if improperly exploiting an electric vehicle– excessively discharging the batteries or overloading the electric vehicle. If a self-converted vehicle does not use an intellectual BMS (battery management system) that can identify and register voltage drop for any individual cell in the high-load regime, e.g. when accelerating, it is difficult to identify and change the cells damaged. In case a cell does not demonstrate a complete failure, it is almost impossible to identify a defect in any regime other than the load regime.

The research developed and compared three different methods for identifying defective battery cells. The methods were approbated on a converted Renault Clio. The experiment involved making voltage measurements in road tests, running the electric vehicle on a roll test bench and making voltage measurements of maximally discharged batteries in the no-load regime. A comparison of the measurement results revealed that the measurements made in the road tests were the most accurate and useful. After the experiment, the defective battery cells were replaced, thereby restoring the performance of the battery pack.

Key words:

battery pack, battery voltage, electric vehicle, test

Investigation into the performance characteristics of electric automobiles by means of a data logger

D. Berjoza¹*, V. Pīrs¹ and I. Jurgena²*

¹Latvia University of Life Sciences and Technologies, Technical Faculty, Institute of Motor Vehicles, 5 J. Cakstes boulevard, LV-3001 Jelgava, Latvia
²University of Life Sciences and Technologies, Faculty of Economics and Social Development, Institute of Business and Management Science, 18 Svetes street LV-3001 Jelgava, Latvia
*Correspondence: dainis.berjoza@llu.lv; inara.jurgena@llu.lv

Abstract:

Fossil fuel deposits are constrained in the world. Various alternative energy sources are introduced in vehicles to limit the depletion of fossil fuel reserves and to reduce environmental pollution. One of the alternative energy sources is electricity. The use of electric automobiles has begun in the Baltic States too, yet accurate performance parameters of the automobiles, which could sometimes differ from the technical characteristics specified, are not always known. Road testing an electric automobile was performed using a data logger that recorded the battery’s voltage, current, temperature and the automobile’s speed. These parameters allowed computing changes in the electric automobile’s power output under various driving regimes, e.g. acceleration or braking. Road testing the electric automobile was done under two driving regimes – urban and non-urban – on a certain route. The experiment represented a full cycle road test, with the batteries fully charged, that lasted until the batteries were discharged to a minimum level, which was limited by the battery management system (BMS). The experiment identified the maximum current as well as the effectiveness of the regenerative braking system.

Key words: