Isothermal Temperature Control for Battery Testing and Battery Model Parameterization

Abstract

The hybrid/ electric vehicle (H/EV) market is very dependent on battery models. Battery models inform cell and battery pack design, critical in online battery management systems and can be used as predictive tools to maximise the lifetime of a battery pack. Battery models require parameterization, through experimentation. Temperature affects every aspect of a battery's operation and must therefore be closely controlled throughout all battery experiments. Today, the private-sector prefers climate chambers for experimental thermal control. However, evidence suggests that climate chambers are unable to adequately control the surface temperature of a battery under test. In this study, laboratory apparatus is introduced that controls the temperature of any exposed surface of a battery through conduction. Pulse discharge tests, temperature step change tests and driving cycle tests are used to compare the performance of this conductive temperature control apparatus (CTCA) against a climate chamber across a range of scenarios. The CTCA outperforms the climate chamber in all tests. In CTCA testing, the rate of heat removal from the cell is increased by two orders of magnitude. The CTCA eliminates error due to cell surface temperature rise, which is inherent to climate chamber testing due to insufficient heat removal rates from a cell under test. The CTCA can reduce the time taken to conduct entropic parameterization of a cell by almost 10 days, a 70% reduction in the presented case. Presently, the H/EV industry's reliance on climate chambers is impacting the accuracy of all battery models. The industry must move away from the flawed concept of convective cooling during battery parameterization.

A Standardised Potentiometric Method for the Effective Parameterisation of Reversible Heating in a Lithium-Ion Cell

“…11,23 Enhanced thermal control provides an opportunity to achieve thermalisation more rapidly at the new temperature set point, thus reducing the time between OCV measurements. 11,24 However, the consequences of rapid temperature change on PTP have not been reported to date.…”

“…Enhanced potentiometric methods.-Future potentiometric methods should build upon the work of Osswald et al 23 and others, 11,24 as well as considering the effect of both PKP and PTP. The specification for optimised procedural design is set out below.…”

A Novel Experimental Technique for Use in Fast Parameterisation of Equivalent Circuit Models for Lithium-Ion Batteries

“…Experimental techniques typically used for the parametrisation of ECMs are electrochemical impedance spectroscopy (EIS) [6][7][8], Galvanostatic intermittent titration technique (GITT) [9][10][11][12][13] and hybrid pulse power characterisation (HPPC) [5,[14][15][16][17]. GITT is the most common technique used by the battery industry, in part because it does not require complex cell-cycling equipment.…”

“…The time to complete a GITT procedure can vary, depending on the accuracy of the experimental data required. One set of GITT experiments lasting up to 80 h are commonly reported [11,13]. These include long rest times which are essential to allow the cell to return to chemical and thermal equilibrium between current loading pulses [20,21].…”

A Novel Experimental Technique for Use in Fast Parameterisation of Equivalent Circuit Models for Lithium-Ion Batteries

“…Experimental techniques typically used for the parametrisation of ECMs are electrochemical impedance spectroscopy (EIS) [6][7][8], Galvanostatic intermittent titration technique (GITT) [9][10][11][12][13] and hybrid pulse power characterisation (HPPC) [5,[14][15][16][17]. GITT is the most common technique used by the battery industry, in part because it does not require complex cell-cycling equipment.…”