The core of the cell models is a signal
voltage controlled by a look-up table OCV (open circuit
voltage) dependent on SOC (state of charge).
However, other dependencies (e.g., on temperature) are not
implemented yet.
Current flowing to or from the battery is measured and
integrated, thus calculating the charge contained in the battery.
The charge contained in the battery with respect to nominal charge
Qnom gives SOC.
The look-up table is parameterized for one cell, therefore input
has to be scaled by 1/(Np*Qnom), and the output has to
be scaled by Ns*OCVmax.
To model self-discharge, a conductor in parallel to the signal voltage and the current sensor is implemented. If self-discharge is specified as zero, the conductor is omitted.
A resistor r0 is connected in series to the signal
voltage, representing the inner resistance of the battery. The
resistance can be specified as linearly dependent on
temperature.
If
CellRCStack instead of CellStack
is chosen, RC-elements are connected in series to model the
transient behaviour of the battery.
Both models can be used for a single cell Ns = Np = 1
as well as a stack built from identical cells.
Note that the total inner resistance Ri is the sum of
the resistance of resistor r0 and the sum of the
resistances of the resistors of the RC-elements.
Additionally to these batteries that model a single cell scaled
by the number of series connected cells Ns and the
number of parallel connected cells Np, single cell
models and stacks are provided in
BatteryStacksWithSensors. The cells are equipped with sensors,
the measured signals are provided in the CellBus.
The stack models contain a matrix of Ns x
Np single cells which can be parameterized differently
to investigate the influence of a degraded cell on the behaviour of
the whole stack, as well as to design battery management systems.
The stack provides the StackBus
which contains Ns x Np cell buses of the
cells. Additionally, the signals of the whole stack - the same
signals as of a single cell - are provided in the BatteryBus.
There are two options of series and parallel connections of cells in stacks:
useAllParallelConnections=true : Np
cells are connected in parallel, and these groups are connected in
series.useAllParallelConnections=false: Ns
cells are connected in series, and these groups are connected in
parallel.For convenience, a block
BusTranscription transfers the signals of all cell buses in the
stack bus to the
StackBusArrays, arranged as Ns x Np
matrix per measurement signal.
For details of parameterization, see UsersGuide.Parameterization.