Electric bicycle battery charging process intelligent control solutions

With the expansion of the urban scale in recent years, the traffic is getting crowded, exhaust emissions of motor vehicle fuel is also one of the main cause of atmospheric pollution. Electric bike because of its lightweight, safe, labor-saving and beneficial to the environmental advantages become

The ideal means of transport.

Lead-acid battery for electric bicycle battery is a chemical widely used in the world power, the product with good reversibility, stable voltage characteristics, long life, applicable to a wide range of rich, raw materials and workmanship

Price advantages of low and has been widely used. However, due to normal battery charging method is unreasonable, their life is significantly shortened. Now many ordinary battery life of only 3 to 5 years, far below the design specifications of 10 to 15 years.

The study found: battery charging process has a greater impact on battery life, that is, the vast majority of the battery is not bad, but a bad charge. Thus, a good performance of the charger on the battery life of the pivotal role

Also reduces the economic input of electric bike users.

The microcontroller has good control and low prices in the lead-acid battery design application microcontroller as a control element can realize the intelligent control of battery charging process, to achieve the best charging effect.

A charger circuit structure

The charger circuit structure as shown in Figure 1, which mains access circuit, high frequency conversion circuit of Part 4 of the 3842 voltage regulator circuit and the secondary rectifier and filter circuit the charging power of the high-frequency switch. Single-chip control circuit, sampling circuit and charging output

The circuit output control circuit.

1.1 high frequency switching charging power supply

Mains access to the circuit through the RS508-type single-phase bridge integrated rectifier circuit 220 V AC converted to 300 V DC. High-frequency conversion circuit is mainly composed by high-frequency transformer T and the MOSFET used in this paper is single-ended flyback circuit.

Single-ended flyback converter is a very important feature of the transformer acts as the inductor, transformer storage, switch cut-off transformer primary side switch (MOSFET tube) conduction energy released into the secondary side. High frequency transformer T has three secondary windings and a feedback winding

Group. Secondary winding on an output optical coupling (TLP250) to provide 15 V power supply, the output of the secondary winding to provide a 5 V power supply for a microcontroller, the secondary winding 3 output constitutes a charge main circuit, the output of the feedback winding provides power, compared with 3842 . While 3842 is

By adjusting the pulse width of the output PWM waveform, thereby adjusting the time of the MOSFET on and off the regulated output of the frequency conversion circuit. Charging the main circuit to output a very pure DC LC-π type filter.

1.2 PIC16C73B MCU control strategy

PIC16C73B control unit in the charging circuit, he is mainly used to achieve the conversion of the state of charge, the temperature compensation control, stop charging control and output drive waveform. He is Microchip's production of a EPROM-based 8-bit high-performance micro

Controller. Compared with other prices are pretty microcontrollers, have a significant improvement in execution speed and code compression. OPT (one-time programming) you can buy products at any time, thus shortening the design of the product with PIC16C73

Development cycle. PIC16C73 microcontroller has superior performance is mainly due to the reduced instruction set (RISC) and Harvard (Harvard) structure, he may use two pipelined instructions to take the number and execution, in addition to the jump instruction needs

Two cycles, all the rest of the instructions can be executed in a single cycle.

1.2.1 control of state transitions

When the battery is charging, the battery voltage sampling circuit immediately on the battery terminal voltage scan cycle, will be sampled terminal voltage signal to give as gifts to PIC16C73B of the way AD mouth convert the microcontroller according to the battery current state

The manner in which to charge the battery.

1.2.2 control of temperature compensation

Charging process, the recombination reaction within the battery to produce large amounts of heat sealing structure of the battery so that the heat difficult to shed, resulting in battery temperature, electrolyte dry, resulting in thermal runaway of the battery. And if there is no temperature compensation,

Can cause the battery charge is low or overcharge and shorten battery life. Acquisition battery temperature sampling circuit to the current battery temperature, using PIC16C73B microcontroller A / D converter, and temperature compensation. Temperature compensation function is started

Charging voltage can be corrected according to the following equation:

Vtc = Vn-TcN (T-20)

Where Vtc temperature compensated voltage Vn uncompensated film; Tc is the temperature compensation coefficient mV / ° C, the compensation coefficient is generally -2 ~~ 4 mV / ° C; N for the values ​​of each set of batteries; T- temperature for the temperature sensor acquisition.

1.2.3 stop charging control

Battery temperature control in the normal charging, the battery temperature is not obvious, however, when the battery overcharge, its internal gas pressure increases rapidly, the negative plate oxidation reflected in the internal heat, the temperature rose rapidly (per minute a few

Celsius degrees). PIC16C73B microcontroller can be filled with judgment batteries according to battery temperature variation, which issued a stop charging control signal.

1.2.4 drive waveform output

Use PIC16C73B microcontroller output frequency of 120 Hz, duty cycle of 0.8 square wave, rectangular wave drive directly after amplification of the optical coupling MOS tube (RPF540,) to charge the battery.

2 charger performance test and test

Charging pulse can fully restore the Wu substances in batteries, battery power, full of rapid, intermittent so that the batteries have sufficient reaction time, reducing the analysis of gas, the battery charging current acceptance rate. Several experimental results

Indicates that the battery is generally 5 ~ 6 h can be filled.
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3 Conclusion

The hardware foundation of the charger circuit to charge the high-frequency switching power supply for control unit, the PIC16C73B microcontroller accurate battery status monitoring and charging control, stop the charge control, control of temperature compensation. Known current basis for charging waveform in charge

During power decreases slowly, very similar to the charging curve of U.S. scientists Maas charge, the battery charge acceptance rate, effectively extending the battery life.