BULETINUL INSTITUTULUI POLITEHNIC DIN IAŞI
buletinul institutului politehnic din iaşi - Universitatea Tehnică ...
buletinul institutului politehnic din iaşi - Universitatea Tehnică ...
- No tags were found...
You also want an ePaper? Increase the reach of your titles
YUMPU automatically turns print PDFs into web optimized ePapers that Google loves.
106 Vlad Marţian et al<br />
there is also the advantage of efficiency which for the electric engine is around<br />
80% -90%.<br />
The main obstacle in producing on a mass scale this type of vehicles is<br />
represented by the storing capacity of the electrical energy i.e. the batteries.<br />
Actually the storing capacity is not enough, so one of the main directions of<br />
research is to improve the storing capacity of the batteries. This increase in<br />
energy density and also the need for drawing high powers form the batteries has<br />
another side effect such as increasing the temperature of the battery. The<br />
working temperature of the battery is a very important parameter, for example<br />
for a Li-ion cell an increase in temperature of 15°C will reduce the life of the<br />
cell by about 50% (Asakura, Shimomura & Shodai, 2003). The temperature has<br />
also another effect on the charge/discharge of the battery and also on the storage<br />
capacity of the battery. These parameters i.e. charge/discharge and storage<br />
capacity is quantified by using the term SOC (State of charge). In the work of<br />
Zheng Popov and others (Zheng, Popov & White, 1997) an optimum<br />
temperature for a battery is around 25°C, even if now there are batteries that can<br />
have a maximum temperature of 85°C (Winston, 2011). The current<br />
discharge/charge rate grows as the temperature approaches the optimum due to<br />
increased ion mobility and also due to modifications of internal resistance of the<br />
battery, but after the optimum the current charge/discharge rate stats to decrease<br />
due to oxidations that happen inside battery. Increasing the temperature over the<br />
functioning domain make the batteries to have a catastrophic failure, and not<br />
only the performance of the battery will be diminished but also irreversible<br />
oxidations occur and the battery becomes useless (Jiangang, et. al., 2006).<br />
For these reasons, toghether with RAAL S.A., we began to investigate the<br />
necesity of a cooling system for batteries equiped in EV and HEV. This paper<br />
presents the first step from many that includes battery modelling, the modelling<br />
of cooling modules, the modelling of an automatic driver, experimental tests of<br />
the cooling modules, and thermal test on the battery pack, etc.<br />
2. Battery Models<br />
The literature has many models which vary in complexity. There are<br />
complex models that use quantum mechanics for describing the battery at<br />
chemical reaction level (Parthasarathy et. al., 2002), (Aron, Girban & Pop,<br />
2010), finite element models that describe the spatial dynamics in the battery<br />
(Sievers, Sievers & Mao, 2010),electrochemical models, electrical equivalent<br />
circuit (Matthias et al., 2005), Dynamic Lumped parameters models, tabulated<br />
battery data models.<br />
To model the battery as close to the reality as possible every model has to<br />
take into account the parameters on which the battery depends on, and these<br />
parameters are a few. One of the most important parameter that the battery has<br />
is the so called state of charge, SOC, or the electrical energy stored in the<br />
battery. This parameter depends on other parameters of the battery as the