Fast and Integrated Chargers for Lithium Ion Batteries

Electric vehicles were introduced in the year of 1908, where they have larger battery for power supply. Now- a- days the technique for charging e-bikes is done either by using grid supply or solar power. This paper says about charging circuit for batteries which uses both solar power and power from the grid to charge the electric vehicles. The charging with solar helps to reduce the emission from power grid. Ever-increasing demand for fuel supply, rising fuel prices, and increased environmental awareness among masses are paving the way for electric vehicles (EVs). Although, in recent years EV market has seen an exponential growth, one of the major challenges faced by this automotive/vehicular market. Now the Indian government had ordered to Indian Vehicle Association to launch the electric vehicles with in 2023. But the charging of electric Batteries has taken more time, which compare to fossil fuel and gas. To overcome this issue use of turbo charger, to reduce the charging time as well as self charging by solar during running time is proposed. The charger uses the source from EB grid and solar as well as at parking time. The results proves that proposed work have reduced the charging time of the lithium ion battery compared to the conventional charging technique and all under controlled temperature raise.


Introduction
In the present scenario the usage of non-conventional fuels for vehicles are in great demand and increasing in price. To reduce the non-conventional fuel usage, electric vehicles are the trending technology for the conventional vehicle replacement, by using e-bikes emission problems will be reduced. Photovoltaic systems may be installed on rooftops to build charging stations. Solar canopies installed on parking lots make an excellent choice or solar-powered EV charging stations. Photovoltaic cells that convert are solar energy into required voltage to charge the battery. As far as electric vehicles are concerned lead acid and lithium ion batteries were most commonly used, Lead acid batteries are lower cost and have higher current carrying capacity [1]. They are heavier in weight and RESGEVT 2020 IOP Conf. Series: Materials Science and Engineering 937 (2020) 012004 IOP Publishing doi:10.1088/1757-899X/937/1/012004 2 have only smaller life time while lithium ion batteries have lower weight, whereas they are higher cost. In this proposed method uses lithium ion battery for electric vehicles. Generally, grid supply is used to charge the batteries of the electric vehicle. The charging time is longer. This method using both grid supply and solar. Where supply for charging the battery is transmitted using both dc and ac converters. Where battery is charged either by grid or solar power [2][3][4]. The availability of both sources for a long duration is insufficient. So the modification technique is done by comparing both the grid supply and solar supply, the efficient supply is given to the battery. In this process only DC supply given to the components. The 230V AC supply from the power grid is rectified and given to the step down transformer which is converted into 12V. The proposed system is designed in such a way that it is easy to charge the battery. The rectifier is used to convert the AC into DC which is fed to the controller. Now calculating state of charge, depth of discharge and input temperature or measure. By using Arduino uno the outputs are displayed in voltage level indicator. Normally charging time for battery is above 7hours [5][6][7], where in this technique charging time is less than 1hours 30 minutes. Below charging circuit is designed, then the smart way methodology is proposed and the analysis of battery charging stated is done. In previous paper A three phase, 6 pulse SCR based rectifier topology is used to charge the battery [8] and constant current, It charges the battery upto 5.7% higher soc in short time compared to CC charging [9-20]. Constant voltage, constant current method is used to charge the battery [21]. But In this method constant voltage, different current is used to charge the battery and also determining soc and temperature of the battery [21 -30]. It explore the optimal charging frequency in AC impedance analysis. The SRC proposed the optimal charging performance indicates the minimum-ac-impedance frequency fZ min [31][32][33]. Realistic battery module is used to charging the battery for minimize the charging time. Two types of system is used to charge the battery, one is on-board and other is off board [33].

Existing methods
In existing system, the battery has charging time with minimum of 6 to 7hrs. It causes major drawback for electric vehicle during emergency. And also in IC engine the diesel or petrol can fill with in 2 or 3 minutes during maximum of period [18][19][20].
Their major drawback in Electric vehicle has slow charging. Some methods are proposed as constant current, different voltage method used to charge the battery but life of the battery is reduced. Constant voltage, constant current method is used to charge the battery but charging time is high.

Problems identified •
The charging of battery is very slower • The petrol engine causes air pollution

Objective
To reduce the charging time of batteries where used in electric vehicle by using fast charger to charge the battery and detecting the percentage and temperature of the battery and then input power will be change by using controller. Figure 1 explains the block diagram of proposed work and it consists of EB source, Renewable energy, Battery, Battery level detector, Arduino, relay, Current controller. The controller detects the SOC and Temperature for the battery to charge. The SOC of the battery is detected using battery level detector and temperature of the battery to be measured using temperature sensor. Arduino plays a major role of the proposed work. It is used as controller of the work. In this paper lithium ion battery is used because lithium ion battery is familiar in EVs now days. During night hours renewable energy will not available, hence controller does the change of input power to EB source.    Figure 2 shows three 36-volt lithium ion battery. Specification of the battery used as shown in table 2. The important things as, cells are connected in series connection to get the battery pack voltage as to meet the EV rated voltage. In this example the resulting pack voltage is 36 volts. In this paper 36V, 6Ah lithium ion battery is used. This assumes that individual batteries are the same capacity of battery pack. Do not mix and match different size of battery pack in the same batteries. Portable equipment needing higher voltages use battery pack with two or more cells connected in series.  Initial current 1A

Hardware Setup
The 230V AC supply from the grid is given to the step down transformers which is converted in series for 12v-36v and also parallel connection for 6A. The rectifier circuit is used to convert the AC supply into DC supply which is fed to the bridge rectifier. In fast charger, the Arduino plays a major role of control the battery charging process. For charging, the power supply is taken from Renewable energy and electricity board is fed to the controller. The input power supply of Renewable energy is compared with EB grid and close the circuit to the battery. The state of charge is measured by battery level detector which gives signal to the controller. If the state of charge is less than 30% the input power of battery is 37.6V,5A, If the state of charge is greater than 30% the input power is 37.6V,3A which is control by current controller. During the high power input, the battery temperature is detected by temperature sensor. If this exceeds the set level, controller stops charging. The temperature range of lithium ion battery is 45'c. If the battery temperature is greater than 37˚c The input power is reduce to 37.6V,1.5A by controller. Finally the charger is designed as based on temperature and state of charge of battery also temperature also increase, due to high temperature battery can result in explosion. And also internal resistance of battery has been increase. Thus proposed fast charger is used to overcome this above drawback and hence it charge the battery based on temperature and percentage of battery as shown in table 3 and its graphical representation as in figure 4.

Conclusion
In this paper, the development of charging circuit for a battery with performance characteristics analysis and also taking into consideration the supply of both the electricity and renewable energy (solar power) was done. The proposed work, utilizes both solar energy and grid electricity for charging lithium ion battery. The voltage from these two sources is compared and which has the high value is used to charge the battery. Electricity is preferred during night hours and also during insufficient solar energy. Arduino is used as controller of the battery charging in different ways. The result table proves that the proposed charger charges the battery with 1h 35 minutes., where the conventional charger takes more than 5 hours to reach the same level. At last, this method concluding that this approach reduces the pollution and increase the usage of EVs as a result creating pollution free environment and reduces the charging time of the lithium ion battery.