BULETINUL INSTITUTULUI POLITEHNIC DIN IAŞI

110 Vlad Marţian et al
The battery model is linked with the rest of the circuit by three
connectors: a positive (p) and negative (n) electric connectors, and a heat
connector (heatPort). Let us explain the thermal part of the battery:
It is well known that the energy conservation law stipulates that the
energy that is stored in a domain must equal the energy that comes in minus the
energy that goes out plus the energy generated inside the domain. The equation
form per unit time, of this law can take the form
dE
d
st
dEin
dE
E
out g
= − + , (3)
dt dt dt
dt
and in the case of a solid domain as the battery, and where we do not have phase
change the Eq. (3) becomes
dT
mCp R i () t hA[ T T ]
d
2
int
amb
t = − − , (4)
where m – mass of the battery, Cp – specific heat capacity of the battery, T –
battery temperature, R int – internal battery resistance, h – thermal convection
coefficient with the outside medium, A – exchange surface of the battery, and
i(t) – the current intensity.
The Eq. (4) is implemented in the battery model as in Fig. 5, except the
Temp sensor, which it is used for linking the temperature to the other
components
Fig. 5 – Thermal model.
4. Simulations
For simulations we have choose a Winston Li-ion battery (Winston,
2011) with a capacity of 60 Ah. The internal resistances and the open circuit
voltage where determined by fitting the charts form the manufacturers data. The
capacitor value was taken to be 4.047kF (Valerie, Ahmad, & Thomas, 2000).
Because we wanted only to test the model, first we have simulated the model