Predictive Model Based Battery Constraints for Electric Motor Control within EV Powertrains

Abstract

This paper presents a method of predicting the maximum power capability of a Li-Ion battery, to be used for electric motor control within automotive powertrains. As maximum power is highly dependent on battery state, the method consists of a pack level state observer coupled with a predictive battery model.Results indicate that the battery state estimation algorithm can estimate a cell State-of-Charge (SoC) within 3%, while pack level simulations show how this method can be enhanced to provide battery pack level estimates, correctly capturing the spread in terms of State of Charge of the cells within the pack, which is essential for accurate maximum power prediction. Tests show that the maximum battery power varies significantly with SoC. At an ambient temperature of 20 • C, as much as a three-fold decrease in power capability is measured for charging power, at SoC values above 90%, and discharging power, at SoC values under 20%.The maximum power prediction algorithm presented in this study is able to correctly predict the maximum battery power over the complete operating range of SoC, at 20 • C.Low temperature maximum discharging power tests were carried out, to investigate electric vehicle cold start scenarios. The tests show a strong impact of temperature on the power which can be withdrawn from the battery. At 35% SoC, 2.5 times less power can be withdrawn from the battery at a temperature of 0 • C, compared to 20 • C.

A Review of Equivalent Circuit Model Based Online State of Power Estimation for Lithium-Ion Batteries in Electric Vehicles

“…As a result, it could aggravate battery aging behaviour and even risk batteries in potential safety issues. Generally, serial or parallel connections are two common configurations to make a battery pack [70].…”

Advances in Li-Ion Battery Management for Electric Vehicles

“…In [21], shorter term prediction horizons are addressed, to provide dynamic battery limitations for electric machine control, such as maximum charging or discharging power. The prediction employed here is much simpler, based on battery current, power and voltage limitations.…”

“…Equivalent circuit modelling has been widely used in the past to describe electro-thermal behaviour of batteries [15], [17], [21]. Computationally efficient, it is a fast enough method for inclusion in BMS algorithms.…”

Optimización del consumo de combustible de un vehículo dependiendo de las condiciones de la carretera

“…Este nivel de carga se define en función de la capacidad de potencia máxima de la batería. Las mediciones realizadas por Rosca et al (2014) y Guan-Ting ( 2012) establecen que el valor de máxima potencia entregada por la batería decrece al disminuir el estado de carga SOC.…”