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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

Description

The EquivCircuit.LiIon component is an equivalent-circuit model of a lithium-ion battery; see the following figure.

R0=expolyRout,soc

R1=expolyRtc1,soc

R2=expolyRtc2,soc

R1C1=expolyTtc1,soc

R2C2=expolyTtc2,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=1sRs3

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=Cmaxsoh

where

  

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=AeexpEaRT

dsdt={kcM1+ksDdiffρseicharging0otherwise

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

mcellcpdTcelldt=PcellQcell

Qflow=ncellQcell

Pcell=icellTcelldUpdTdUndT+icellvcellvoc

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=hAcellTcellTamb

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.

Variables

Name

Units

Description

Modelica ID

Tcell

K

Internal temperature of battery

Tcell

i

A

Current into battery

i

v

V

Voltage across battery

v

Connections

Name

Type

Description

Modelica ID

p

Electrical

Positive pin

p

n

Electrical

Negative pin

n

soh

Real output

State of health [0..1]; available when include degradation effects is enabled

soh

soc

Real output

State of charge [0..1]

soc

Cin

Real input

Sets capacity of cell, in ampere hours; available when use capacity input is true

Cin

Degradation Parameters

Name

Default

Units

Description

Modelica ID

Ae

1.2

ms

Factor for reaction rate equation

Ae

D0

1.8·10−19

m2s

Diffusion coefficient at standard conditions

D0

Ea

10000

Jmol

Activation energy

Ea

M

0.026

kgmol

Molar mass of SEI layer

M

Rs

2·10−6

m

Radius of particles of active material in anode

Rs

SoH0

1

 

Initial state-of-health: 0SoH01

SoH0

c

5000

molm3

Molar concentration of electrolyte

c

κ

0.001

mΩ

Specific conductivity coefficient

kappa

ρsei

2600

kgm3

Density of SEI layer

rho_sei

Basic Parameters

Name

Default

Units

Description

Modelica ID

Ncell

1

 

Number of cells, connected in series

Ncell

CA

1

A·h

Capacity of cell; available when use capacity input is false

C

SOC0

1

 

Initial state-of-charge [0..1]

SOC0

SOCmin

0.01

 

Minimum allowable state-of-charge

SOCmin

Rcell

0.005

Ω

Fixed cell resistance, if use cell resistance input is false

Rcell

Basic Thermal Parameters

Name

Default

Units

Description

Modelica ID

Tiso

298.15

K

Constant cell temperature; used with isothermal heat model

Tiso

cp

750

JkgK

Specific heat capacity of cell

cp

mcell

0.014

kg

Mass of one cell

mcell

h

100

Wm2K

Surface coefficient of heat transfer; used with convection heat model

h

Acell

0.0014

m2

Surface area of one cell; used with convection heat model

Acell

Tamb

298.15

K

Ambient temperature; used with convection heat model

Tamb

Electrode Chemistry Parameters

Name

Default

Units

Description

Modelica ID

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 JmolK.

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

Lithium Manganese Oxide

 

Lⅈ1.156Mn1.844O4

Lithium Manganese Oxide

 

LⅈNⅈ0.8Co0.15Al0.05O2

Lithium Nickel Cobalt Aluminum Oxide

NCA

LⅈNⅈ0.8Co0.2O2

Lithium Nickel Cobalt Oxide

 

LⅈNⅈ0.7Co0.3O2

Lithium Nickel Cobalt Oxide

 

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

Chemical composition

Chemical name

Common name

LⅈC6

Lithium Carbide

Graphite

LⅈTⅈO2

Lithium Titanium Oxide

 

Lⅈ2Tⅈ5O12

Lithium Titanate

LTO

General Parameters

Name

Default

Units

Description

Modelica ID

Rout

0.11,−50,0.0075

 

expoly array for series resistance

Rout

Rtc1

0.05,−29,0.0074

 

expoly array for short time-constant resistance

Rtc1

Ttc1

3.5,−10,10.5

 

expoly array for short time-constant duration

Ttc1

Rtc2

1,−150,0.008

 

expoly array for long time-constant resistance

Rtc2

Ttc2

−500,−20,710

 

expoly array for long time-constant duration

Ttc2

An exponential-polynomial (expoly) is a polynomial with an exponential term included. Its coefficients are given by a one-dimensional array, k, such that ⅇxpolyk,soc=k1ⅇxpk2soc+k3+k4soc+k5soc2+.

References

  

[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]