State-of-charge determination

The inner part of the DL consists of the adsorption layer and specifically adsorbed counterions. The state of charge-determining ions and specifically adsorbed counterions depend on potentials which are determined by their localisation. 

Shen Y (2010) Adaptive online state-of-charge determination based on neuro-controller and neural network. Energy Convers Manag 51 1093-1098. doi I0.1016/j.enconman.2009.12.015... 

Piller S, Perrin M, Jossen A (2001) Methods for state-of-charge determination and their applications. J Power Sources 96 113-120. doi 10.1016/50378-7753(01)00560-2... 

Comparison between state of charge determination methods for lithium-ion batteries based on the measurement of impedance, voltage and coulomb counting... 

Martinet, S., Durand, R., Ozil, R. et al. (1999) Apphcation of electrochemical noise analysis to the study of batteries state-of-charge determination and overvoltage detection. Journal of Power Sources, 83, 93-99. 

We shall be interested in determining the effect of electrolytes of low molecular weight on the osmotic properties of these polymer solutions. To further simplify the discussion, we shall not attempt to formulate the relationships of this section in general terms for electrolytes of different charge types-2 l, 2 2, 3 1, 3 2, and so on-but shall consider the added electrolyte to be of the 1 1 type. We also assume that these electrolytes have no effect on the state of charge of the polymer itself that is, for a polymer such as, say, poly (vinyl pyridine) in aqueous HCl or NaOH, the state of charge would depend on the pH through the water equilibrium and the reaction... 

The RHSE has the same limitation as the rotating disk that it cannot be used to study very fast electrochemical reactions. Since the evaluation of kinetic data with a RHSE requires a potential sweep to gradually change the reaction rate from the state of charge-transfer control to the state of mass transport control, the reaction rate constant thus determined can never exceed the rate of mass transfer to the electrode surface. An upper limit can be estimated by using Eq. (44). If one uses a typical Schmidt number of Sc 1000, a diffusivity D 10 5 cm/s, a nominal hemisphere radius a 0.3 cm, and a practically achievable rotational speed of 10000 rpm (Re 104), the mass transfer coefficient in laminar flow may be estimated to be ... 

It must be noted that there are a number of more or less arbitrary assumptions made in this work30,31 which need justification, as well as parameters whose values should be calculated rather than assumed. For instance, the importance of the distance dl9 taken as equal to Rc, has been mentioned. In principle, the value of this distance is a consequence of the forces between components of the metal and molecules of solvent, and would be calculated in a consistent model of the complete interface. This was pointed out by Yeager,18 who noted that the electron density tail of the metal determines the distance of closest approach of solvent in the interface, as well as the behavior of the solvent dipoles on the surface. Since changing qM will move the electron density tail in and out, dx should depend on the state of charge of the interface. In fact, it turns out31 that if dx varies linearly with surface charge according to... 

The thermal energy generated or absorbed by an electrochemical cell is determined first by the thermodynamic parameters of the cell reaction, and second by the overvoltages and efficiencies of the electrode processes and by the internal resistance of the cell system. While the former are generally relatively simple functions of the state of charge and temperature, the latter are dependent on many variables, including the cell history. 

Each of these reactions produces the insoluble substance PbSO, lead sulfate, which adheres to the plates. As the cell is discharged sulfuric acid is removed from the electrolyte, which decreases in density. The state of charge or discharge of the cell can accordingly be determined with use of a hydrometer, by measuring the density of the electrolyte (Fig. 2-13). 

The problem of the charge state of ions penetrating matter is one of the most relevant questions for studies on the interaction of ions with solids. It is known that after some penetration distance the ions reach a state of charge equilibrium determined by the competition between capture and loss processes [2,7]. As a result of this equiUbrium the ions acquire a mean ionization charge as well as a stationary distribution of charge states around q. 

Basic functional controls will include those in Table 11.19. Most of the values can be derived from a straightforward transfer function but several, particularly those determining maximum charge current, discharge current, and state-of-charge, will require careful scrutiny of the definition, calculation, and error analysis. 

Another problem is that of balance between single cells in a multicell battery. Such batteries are balanced when all cells (preferably of the same type) have the same capacity and the same state of charge (SOC). In case of a mismatch between cells connected in series the battery s ampere-hour capacity is determined by the cell with the least available ampere-hour capacity. In case of cells connected in parallel, a failure (e.g., short circuit) of one of the cells can lead to the failure of the whole battery. 

The state of charge of the battery or the maximum possible capacity after a certain period of operation in practice only can be determined by a real test. 

Li-Ion batteries require electronic controls to prevent cell voltage from exceeding predetermined high- and low-voltage limits. Voltage excursions outside these limits can damage the cell and may create safety issues in the cell. The electronic controls also determine the state-of-charge and stop-cell operation. 

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