1. INTRODUCTION
Battery electric vehicle is a key driver of production units in lead acid batteries, nickel-cadmium batteries, nickel-hydride batteries, metal, lithium batteries and fuel cells are more commonly used batteries because the high energy that large, light weight, good temperature characteristics, low pollution memory effect is not obvious characteristics such as nickel-metal hydride batteries used in electric vehicles are common. However, due to poor loading method, resulting in the life of the Laptop battery pack is well below the stipulated life. It’s much the battery is not bad but is filled with bad, good or bad for the battery charger can be seen a great impact on life expectancy. For this reason, this paper presents a three-stage program load control using smart charger design can actually improve the pricing efficiency and prolong battery life.
2. Control method developed
Methods of charge termination control are commonly used: a method of controlling timing, method of control voltage, the current method of control and integrated control laws.
Timing Control Act refers to the timing system to control the charging time, time has no value when they arrive on the Dell Inspiron E1705 battery to stop. Do not load. Commonly used in the law of voltage control, including the highest voltage (Vmax), the incremental negative voltage method (△ V), zero voltage increment method (0 △ V) commonly used in law to control temperature, including the method of maximum temperature (Tmax), method of filling temperature (△ T). Percentage change in temperature (T △ / △ t), the method at low temperature (Tmin). Integrated control method is the use of combined methods of controlling the above-mentioned in several control methods.
Compared with traditional fixed voltage and constant current charging method of three theories fees can greatly improve the efficiency of the battery. Three stages of indictment charging the first constant current and constant tension, the final adoption of floating Chong Chongdian. If the battery pack in deep discharge state of the former are still borne by the preload.
3. System hardware structure
3.1 Design comprehensive material
Subject to the nickel-metal hydride rechargeable VGP-BPS2C batteries, using the method of voltage and current feedback to achieve constant current, constant voltage goals, while the charge in the testing process and control parameters.
The program switching power supply maximum output of 2.4kW, AC input range of 1 76V-264V, charger circuit comprises essentially the main circuit and the circuit load auxiliary control of two parts, the whole process of operation of the circuit: 220V single phase power supply across the bridge.
Rectifier is filtered by the capacitor to move about 300V DC, after a composition by the four-bridge IGBT inverter with high frequency alternating current through the high frequency transformer coupled to the secondary side, and then through the rectifier D1 , rectifier D2 and finally by the inductor L 2 and capacitor C8 filtered to provide a stable DC. Following three tasks at each stage of the charging voltage and load current are different. Thus, as the charging process using the ATMEGA8 MCU control equipment, rechargeable batteries, charging SCM detect the load current, charging voltage, the battery temperature to prevent the circuit from overvoltage and overcurrent, the battery temperature is too high, you can also detect the battery voltage and current values to determine if the transition to the next stage of a fee. Now, every step of the SCM is given the value of the charging voltage or current value, and the corresponding sample obtained from the voltage and current through the UCC3895 phase-shifted PWM control chip to change the value to change the power tubes on time, to achieve at different stages of a stable output value of different purposes.
3.2 describes the circuit pressure maintenance
Main circuit charging circuit full bridge inverter. IGBT H-bridge with four components T1 T3 tube Q4 Q2, Ql and Q4 formed ahead of the bridge arm to achieve zero voltage turn on and off, Q2 and Q3 GAL composed Arm Bridge to zero-current turn on and off. Labor and Q2 of the inverse of the driving voltage, Q 3 and Q 4 of the control voltage is also the inverse, Q 1 and Q 2 and Q 3 and Q 4 to turn the switching dead time can be is in phase transfer controller UCC389S controlled by adjusting the mobile phase T4 ahead of the bridge arm to adjust the conduction time common to adjust the duty cycle to achieve the goal of changing the output hp F2024A battery power. Q2 and Q3 GAL consist of the theory of arms control and the bridge ahead of the same bridge arm.