Electric Vehicle Li-Ion Battery Evaluation Based on Internal Resistance Analysis

Abstract

Internal resistance (IR) is considered one of the most important parameters of a battery, as it is used to evaluate the battery's power performance, energy efficiency, aging mechanisms or equivalent circuit modeling. In addition, in electric vehicle (EV) applications, the IR provides essential information related with regenerative braking capabilities, dynamic charge and discharge efficiencies, or physical degradation of the battery. This work aims to provide the insight details of the IR of a battery under several testing conditions and methods, to present its practical implications on EVs. The experimental tests are carried out on lithium iron phosphate (LFP) batteries ranging from 16 Ah to 100 Ah, suitable for its use in EVs. We study the IR dependency with battery's capacity, SOC and the charge/discharge rate; also, the convenience of using a certain IR measurement method is evaluated. Furthermore, the main results are put into context for practical EV applications, to enhance the design of battery management systems (BMS) in relation with the system's energy efficiency.

Analysis of the effect of resistance increase on the capacity fade of lithium ion batteries

“…Further, the model of the present study assumes that the effect of resistance increase is similar at both the end of charge and end of discharge. However, in reality, resistance is a function of both charge/discharge current and SOC of the battery . Incorporating these effects will further improve the fidelity of the model.…”

“…However, in reality, resistance is a function of both charge/discharge current and SOC of the battery. 27,51 Incorporating these effects will further improve the fidelity of the model. Increase in resistance at a particular SOC (and correspondingly at a particular OCV) can be computed utilizing techniques such as incremental capacity analysis, 26 and this can be used for obtaining estimates of OCV BOD and OCV EOD , which can in turn be utilized for computing the loss of capacity due to resistance increase alone.…”

Discharge Capacity Estimation for Lithium–Ion Battery Packs with Cells in Parallel Connection Based on Current Prediction of In‐Pack Cells

“…Fort he internal resistance test, so far, there has not been au nified standard for measuring the internal resistance of lithium-ion batteries.Acomparison of several methods for the internal resistance of lithium-ion cells was provided by Schweiger et al [20,21] We conducted ap ulse current test on the cells at 5% SOC intervals from 95 to 5%.A2hstandby period followed each current pulse.T he internal resistance identification results could be obtained at different SOC points.B yu sing these points,t he parameters in Equation (5) could be estimated.…”

Unidirectional voltage converter for battery electric vehicle ultrafast charger

“…with 3C current. The possibility to charge an EV battery Model of 100c4ch (800Ah/320 V/256kWh) battery set made of the Li-ion cells LPF200AHA with DC/DC converter powered from 600 V DC microgrid (Marra 2013;Anseán et al 2009) with 3C current depends on its cooling capability, as the losses during charging (P s = R zb ÁI zb 2 ) increase three times to 3 9 5 kW = 15 kW. During continuous operation and while charging the battery, its temperature may not exceed 65°C (GW 2020).…”