Equivalent Circuit Nickel-Metal Hydride
Equivalent-circuit model of a nickel-metal hydride battery
Basic Thermal Parameters
The EquivCircuit.NiMH component is an equivalent-circuit model of a nickel-metal hydride battery; see the following figure.
Select the thermal model of the battery from the heat model drop-down list. The available models are: isothermal, external port, and convection.
The isothermal model sets the cell temperature to a constant parameter, Tiso.
The external port model adds a thermal port to the battery model. The temperature of the heat port is the cell temperature. The parameters mcell and cp become available and are used in the heat equation
where Pcell is the heat generated in each cell, including chemical reactions and ohmic resistive losses, Qcell is the heat flow out of each cell, and Qflow is the heat flow out of the external port.
The convection model assumes the heat dissipation from each cell is due to uniform convection from the surface to an ambient temperature. The parameters mcell, cp, Acell, h, and Tamb become available, as does an output signal port that gives the cell temperature in Kelvin. The heat equation is the same as the heat equation for the external port, with Qcell given by
The capacity of a cell can either be a fixed value, CA, or be controlled via an input signal, Cin, if the use capacity input box is checked.
The resistance of a cell can either be a fixed value, Rcell, or be controlled via an input signal, Rin, if the use resistance input box is checked. This resistance is in addition to the resistance of the equivalent circuit.
State of Charge
A signal output, soc, gives the state-of-charge of the battery, with 0 being fully discharged and 1 being fully charged.
The parameter SOCmin sets the minimum allowable state-of-charge; if the battery is discharged past this level, the simulation is either terminated and an error message is raised, or, if the allow overdischarge parameter is true, a warning is generated. A similar effect occurs if the battery is fully charged so that the state of charge reaches one; the simulation is terminated unless allow overcharge is true.
The parameter SOC0 assigns the initial state-of charge of the battery.
State of charge [0..1]
Sets capacity of cell, in ampere hours; available when use capacity input is true
Sets resistance of cell, in ohms; available when use cell resistance input is true
Internal temperature of battery
Current into battery
Voltage across battery
Number of cells, connected in series
Capacity of cell; available when use capacity input is false
Initial state-of-charge [0..1]
Minimum allowable state-of-charge
Fixed cell resistance, if use cell resistance input is false
True allows simulation to continue with 1<SoC
True allows simulation to continue with SoC<SoCmin
use capacity input
True allows enables the Cin input port
use cell resistance input
True allows enables the Rin input port
Constant cell temperature; used with isothermal heat model
Specific heat capacity of cell
Mass of one cell
Surface coefficient of heat transfer; used with convection heat model
Surface area of one cell; used with convection heat model
Ambient temperature; used with convection heat model
Temperature coefficient of potential of positive electrode
Temperature coefficient of potential of negative electrode
expoly array for series resistance
expoly array for short time-constant resistance
expoly array for short time-constant duration
expoly array for long time-constant resistance
expoly array for long time-constant duration
An exponential-polynomial (expoly) is a polynomial with an exponential term included. Its coefficients are given by a one-dimensional array, k, such that ⅇxpoly⁡k,soc=k1⁢ⅇxp⁡k2⁢soc+k3+k4⁢soc+k5⁢soc2+⋯.
 Chen, M. and Rincón-Mora, G.A., Accurate electrical battery model capable of predicting runtime and I-V performance, IEEE Transactions of Energy Conversion, Vol. 21, No. 2, 2006.
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