MaplesoftBattery
EquivCircuit.LiIon — Equivalent-circuit model of a lithium-ion battery
Description
Variables
Connections
Degradation Parameters
Basic Parameters
Basic Thermal Parameters
Electrode Chemistry Parameters
General Parameters
References
The EquivCircuit.LiIon component is an equivalent-circuit model of a lithium-ion battery; see the following figure.
R0=expoly⁡Rout,soc
R1=expoly⁡Rtc1,soc
R2=expoly⁡Rtc2,soc
R1⁢C1=expoly⁡Ttc1,soc
R2⁢C2=expoly⁡Ttc2,soc
Degradation
The gradual decay, with use, of a cell's capacity and increase of its resistance is modeled by enabling the include degradation effects boolean parameter. Enabling this feature adds a state-of-health (soh) output to the model. This signal is 1 when the cell has no decay and 0 when is completely decayed.
The soh output is given by
soh=1−sRs3
where
s is thickness of the solid-electrolyte interface (SEI),
Rs is radius of the particles of active material in the SEI.
The decay of the capacity is
C=Cmax⁢soh
C is the effective capacity, and
Cmax is the specified capacity equal to either the parameter CA or the input Cin.
The additional series resistance added to a cell is
Rsei=sκ
with κ a parameter of the model.
The following equations govern the increase in the thickness of the SEI layer (s).
k=Ae⁢exp⁡−EaR⁢T
dsdt={k⁢c⁢M1+k⁢sDdiff⁢ρseicharging0otherwise
Thermal Effects
Select the thermal model of the battery from the heat model drop-down list. The available models are: isothermal, external port, and convection.
Isothermal
The isothermal model sets the cell temperature to a constant parameter, Tiso.
External Port
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
mcell⁢cp⁢dTcelldt=Pcell−Qcell
Qflow=ncell⁢Qcell
Pcell=icell⁢Tcell⁢dUpdT−dUndT+icell⁢vcell−voc
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.
Convection
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
Qcell=h⁢Acell⁢Tcell−Tamb
Capacity
The capacity of the battery can either be a fixed value, CA, or be controlled via an input signal, Cin, if the use capacity input box is checked.
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 terminated and an error message is raised. This prevents the battery model from reaching non-physical conditions. A similar effect occurs if the battery is fully charged so that the state of charge reaches one.
The parameter SOC0 assigns the initial state-of charge of the battery.
Name
Units
Modelica ID
Tcell
K
Internal temperature of battery
i
A
Current into battery
v
V
Voltage across battery
Type
p
Electrical
Positive pin
n
Negative pin
soh
Real output
State of health [0..1]; available when include degradation effects is enabled
soc
State of charge [0..1]
Cin
Real input
Sets capacity of cell, in ampere hours; available when use capacity input is true
Default
Ae
1.2
ms
Factor for reaction rate equation
D0
1.8·10−19
m2s
Diffusion coefficient at standard conditions
Ea
10000
Jmol
Activation energy
M
0.026
kgmol
Molar mass of SEI layer
Rs
2·10−6
m
Radius of particles of active material in anode
SoH0
1
Initial state-of-health: 0≤SoH0≤1
c
5000
molm3
Molar concentration of electrolyte
κ
0.001
mΩ
Specific conductivity coefficient
kappa
ρsei
2600
kgm3
Density of SEI layer
rho_sei
Ncell
Number of cells, connected in series
CA
A·h
Capacity of cell; available when use capacity input is false
C
SOC0
Initial state-of-charge [0..1]
SOCmin
0.01
Minimum allowable state-of-charge
Rcell
0.005
Ω
Fixed cell resistance, if use cell resistance input is false
Tiso
298.15
Constant cell temperature; used with isothermal heat model
cp
750
Jkg⁢K
Specific heat capacity of cell
mcell
0.014
kg
Mass of one cell
h
100
Wm2⁢K
Surface coefficient of heat transfer; used with convection heat model
Acell
0.0014
m2
Surface area of one cell; used with convection heat model
Tamb
Ambient temperature; used with convection heat model
chem+
LiCoO2
Chemistry of the positive electrode
chem_pos
chem−
Graphite
Chemistry of the negative electrode
chem_neg
The chem_pos and chem_neg parameters select the chemistry of the positive and negative electrodes, respectively. They are of types MaplesoftBattery.Selector.Chemistry.Positive and MaplesoftBattery.Selector.Chemistry.Negative. The selection affects the variation in the open-circuit electrode potential and the chemical reaction rate versus the concentration of lithium ions in the intercalation particles of the electrode.
If the Use input option is selected for either the positive or negative electrode, a vector input port appears next to the corresponding electrode. The port takes two real signals, U and S, where U specifies the potential in volts at the electrode and S specifies the entropy in Jmol⁢K.
If any of the chem_pos materials LⅈNⅈO2, LⅈTⅈS2, LⅈV2O5, LⅈWO3, or NaCoO2 is selected, the isothermal model is used.
Supported positive electrode materials
Chemical composition
Chemical name
Common name
LⅈCoO2
Lithium Cobalt Oxide
LCO
LⅈFⅇPO4
Lithium Iron Phosphate
LFP
LⅈMn2O4
Lithium Manganese Oxide
LMO
LⅈMn2O4 - low plateau
Lⅈ1.156Mn1.844O4
LⅈNⅈ0.8Co0.15Al0.05O2
Lithium Nickel Cobalt Aluminum Oxide
NCA
LⅈNⅈ0.8Co0.2O2
Lithium Nickel Cobalt Oxide
LⅈNⅈ0.7Co0.3O2
LⅈNⅈ0.33Mn0.33Co0.33O2
Lithium Nickel Manganese Cobalt Oxide
NMC
LⅈNⅈO2
Lithium Nickel Oxide
LⅈTⅈS2
Lithium Titanium Sulphide
LⅈV2O5
Lithium Vanadium Oxide
LⅈWO3
Lithium Tungsten Oxide
NaCoO2
Sodium Cobalt Oxide
Supported negative electrode materials
LⅈC6
Lithium Carbide
LⅈTⅈO2
Lithium Titanium Oxide
Lⅈ2Tⅈ5O12
Lithium Titanate
LTO
Rout
0.11,−50,0.0075
expoly array for series resistance
Rtc1
0.05,−29,0.0074
expoly array for short time-constant resistance
Ttc1
3.5,−10,10.5
expoly array for short time-constant duration
Rtc2
1,−150,0.008
expoly array for long time-constant resistance
Ttc2
−500,−20,710
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+⋯.
[1] 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.
See Also
Battery Library Overview
MaplesoftBattery[EquivCircuit][Overview]
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