Smart and Accurate State-of-Charge Indication in Portable Applications

Accurate State-of-Charge (SoC) and remaining run-time indication for portable devices is important for the user-convenience and to prolong the lifetime of batteries. However, the known methods of SoC indication in portable applications are not accurate enough under all practical conditions. The method presented in this paper aims at designing and testing an SoC indication system capable of predicting the remaining capacity of the battery and the remaining run-time with an accuracy of 1 minute or better under all realistic user conditions, including a wide variety of load currents and a wide temperature range. At the moment Li-ion is the most commonly used battery chemistry in portable applications. Therefore, the focus is on SoC indication for Li-ion batteries. The basis of the proposed algorithm is current measurement and integration during charge and discharge state and voltage measurement during equilibrium state. Experimental results show the effectiveness of the presented novel approach for improving the accuracy of the SoC indication

A Real-Time evaluation system for a state-of-charge indication algorithm

The known methods of State-of-Charge (SoC) indication in portable applications are not accurate enough under all practical conditions. This paper describes a real- time evaluation LabVIEW system for an SoC algorithm, that calculates the SoC in [%] and also the remaining run-time available under the valid discharge conditions. With the described system the accuracy of the SoC algorithm and its validity can be determined. The final goal of the SoC algorithm is to predict the remaining capacity of the battery and the remaining run-time with an accuracy of 1 minute or better under all realistic user conditions, including a wide variety of load currents and a wide temperature range. The basis of the SoC algorithm is current measurement and integration during charge and discharge state and voltage measurement during equilibrium state. Experimental results show the testing ability of the real-time evaluation system and the effectiveness of the novel approach for improving the accuracy of the SoC indication

Apparatus and method for determination of the state-of-charge of a battery when the battery is not in equilibrium

The invention relates to a method and an apparatus, like a charger for determining the state-of-charge of a battery which has been charged or discharged and which has not reached its equilibrium state, the method comprising the steps of determining the EMF of the battery by extrapolation of the battery voltage sampled during relaxation after the charge or the discharge process, wherein the extrapolation is based on a model using only variables sampled during the relaxation process and deriving the state-of-charge from the EMF of the battery by using a predetermined relation between the EMF and the state-of- charge. This method is a voltage-prediction method without the need to store parameters beforehand.; Instead, the voltage relaxation end value is determined based on the measured first part of a voltage relaxation curve and mathematical optimisation/fitting of a function to this measured part of the relaxation curve

Optimization of nitridation conditions for high quality inter-polysilicon dielectric layers

Nitridation of deposited high temperature oxides (HTO) was studied to form high quality inter-polysilicon dielectric layers for embedded non volatile memories. Good quality dielectric layers were obtained earlier by using an optimized deposition of polysilicon and by performing a post-dielectric anneal in a rapid thermal processor. In the present paper the quality is further improved by means of optimization of the post-dielectric anneal. The influence of temperature, time and pressure during annealing on the electrical properties is investigated. Electrical characterization by means of charge-to-breakdown (Qbd) and I-V measurements on simple capacitor structures evaluates the electrical properties of the layers. It is shown that an (optimized) rapid thermal N2O anneal leads to a very high charge to breakdown (Qbd ¿ 25 C/cm2), low charge trapping and low leakage currents

Integration trends in monolithic power ICs: Application and technology challenges

This paper highlights the general trend towards further monolithic integration in power applications by enabling power management and interfacing solutions in advanced CMOS nodes. The need to combine high-density digital circuits, power-management circuits, and robust interfaces in a single technology platform requires the development of additional process options on top of baseline CMOS. Examples include high-voltage devices, devices to enable area-efficient ESD protection, and integrated capacitors and inductors with high quality factors. The use of bipolar devices in these technologies for protection and control purposes in power applications is also addressed

On experiment design for parameter estimation of equivalent-circuit battery models

Using Li-ion batteries in applications, such as E-bikes, requires proper battery management. In battery management, model-based state estimation techniques can be used to estimate the State-of-Charge, for which it is common to consider an Equivalent Circuit Model (ECM). Accurate model parameters are necessary to ensure a certain quality of the state estimate. The ECM parameters highly depend on the experiment used to determine them and different choices of these experiments can be found in the literature. In this paper, we investigate the experiment design for parameter estimation both quantitatively and qualitatively. The use of pulsed currents for parameter estimation, which is a commonly used experiment, is compared to using data from a road test with the E-bike. The results quantify how much the state estimation improves when the parameters are estimated using data that represent the intended application

Rapid empirical battery electromotive-force and overpotential modelling using input-output linear parameter-varying methods

In this paper, battery overpotential model identification approaches based on local and global Linear Parameter-Varying (LPV) input–output models are developed. Key features such as model structure, number of local models, and type and order of basis functions are considered. The LPVcore toolbox (Boef, 2021) has been used to solve the global identification problems. Furthermore, an iterative scheme is proposed which identifies a complete empirical battery model, i.e., both the ElectroMotive Force (EMF), also known as open-circuit voltage, and the overpotential model. This is achieved by iteratively obtaining an EMF realisation by (1) subtracting the modelled overpotential from a measured terminal voltage resulting from Constant-Current (CC) (dis)charging, and (2) using this EMF to calculate the overpotential from dynamic (dis)charging data and identifying an overpotential model using the LPV methods. This approach results in an empirical battery model with a precision similar (around 4 mV root-mean-square error in the range between 100% and 20% SoC) to models identified through a common cascaded approach in which the EMF is obtained separately from, e.g., pulse-(dis)charge data, but requires less measurement data resulting in a reduction factor in the order of 7 to 35 in terms of required experiment time

Electronic network modeling of rechargeable batteries: II: The NiCd system

Based on the concept of a defined sealed rechargeable NiCd battery, the mathematics of the various electrochemical and physical processes occurring inside the battery are described. Subsequently, these sets of mathematical equations are clustered and converted into an electronic network model. Introducing the relevant electrochemical and physical parameters, the one-dimensional model is shown to be capable of simulating not only the development of the cell voltage during (over)charging and (over)discharging, but also of simultaneously calculating the development of the internal gas pressure. Considering the thermal dependencies of the various electrochemical reactions and those of the battery environment, the temperature development and the mutual interaction with the voltage and gas pressure can also be calculated. Since the electronic network approach gives access to all partial currents flowing through the different reaction paths inside the battery, it is easy to visualize what processes are occurring during battery operation. This is, for example, illustrated for the two-step overdischarge process, indicating that, respectively, the Cd and O2 charge-transfer reactions play a dominant role under these conditions. Electronic network simulations are shown to be not only restricted to direct current applications but are also applicable to processes, like open-circuit voltage relaxation and self-discharge behavior