Talking about the mechanism of fast charging and intelligent rapid charging system design
Since 1859, the French physicist Plante invented lead-acid batteries for 140 years. The lead-acid battery has the advantages of low cost, wide applicability, good reversibility, high current discharge performance, high single cell voltage, and can be made into a sealed and maintenance-free structure, and is widely used in vehicle startup, post and telecommunications, and electric power. , railways, mines, mining, computer UPS and other fields. Storage batteries are also an important energy source for the national economy and national defense construction. In many industries, batteries with large capacity, long cycle life, short charging time, and low prices are also urgently needed. Rapid charging technology has also become a key technology, and it has a very important impact on the use of batteries. At present, domestic and foreign countries are constantly studying this technology, and the introduction of computer control in the rapid charging technology is very effective, and has very obvious economic benefits. The SCM is favored by the industry for its low cost and flexible control method. This system is based on the AT89C2051 single-chip microcomputer, which integrates measurement and control into an intelligent fast charging system.
2. The mechanism of rapid chargingLead-acid battery rapid charging technology is developed on the basis of conventional charging technology. No matter which charging system is adopted for charging, the charging process of lead-acid battery must follow the bipolar sulfation theory, ie its chemical reaction equation. for:
According to the conventional charging method, the ampacity of the charging current should not exceed the ampere-hours at which the battery is to be charged. In this way, it can be ensured that the gas and temperature rise conditions meet the requirements throughout the charging process. Therefore, conventional battery charging methods use constant-current or constant-current charging with a small current, and the charging time is as long as 10 to 20 hours, which brings a lot of inconvenience to practical use. In order to shorten the charging time of the battery, research and development of rapid charging methods and technologies have been constantly conducted at home and abroad.
After JA Mas proposed the three laws of battery charging in 1967, these theories became the basis for our research on fast charging technology. The battery has the following charging characteristics:
(1) Battery charge acceptance varies with depth of discharge. If the current is discharged with the same size, the more the discharged power, the higher the charge acceptance rate α and the larger the charge acceptance current. That is, there is the following relationship:
I0 - The maximum initial current value at the start of charging.
C - discharge capacity.
K - constants can be determined experimentally.
(2) Charging acceptance rate for any given depth of discharge:
And because I0=αC, so
Id - discharge current.
The constants K and k can be derived from experiments.
The above formula shows that the charge acceptance rate of the battery depends on its discharge history. A battery with a small discharge current for a long time has a low charge acceptance rate. Conversely, a battery discharged with a large current for a short time has a high charge acceptance rate.
(3) A battery is discharged at several discharge rates, and its charge acceptance current is the sum of the currents received at each discharge rate. That is: It = I1+I2+I3+......
Obedience at the same time:
It - always accepts current.
Ct - The total amount of electricity discharged.
Αt - The total charge acceptance rate.
The discharge can increase the amount of discharged Ct, and also increase the total charge acceptance current It. Therefore, the battery is properly discharged before or during charging, which will increase the charge acceptance rate αt.
According to Maxim's theory, we control the charging current in the charging process in real time, that is, charging with a large current, and during the charging process, the charging is stopped briefly. The discharge pulse is added during the stop charging to break the natural acceptance characteristic of the battery charging index curve. limits. However, theory and practice have proved that the charge and discharge of the battery is a very complex electrochemical process. It can be known from the electrochemical mechanism of rapid charge that the important factor affecting fast charge is the electrode polarization of the battery, which is common to all secondary batteries. , including ohmic polarization, concentration polarization, and electrochemical polarization. The electrode polarization of the battery can be eliminated by adding a discharge pulse in the charging process. Therefore, in order to achieve rapid charging, many aspects of control are needed. The control features are:
(1) Multivariables - such as the temperature within the battery, the size of the charging current, the interval between charges, and the setting of the depolarization pulse.
(2) Non-linearity—The charging current should gradually decrease as charging progresses, otherwise it will cause an increase in gas output and temperature rise.
(3) Discreteness--As the battery discharge status, use, and storage history are different, even the same type of battery and the same capacity of the same type of battery are not the same.
For such a complicated charging process, it is obviously difficult to control using a conventional charging circuit, and therefore, the effect of quick charging is also affected. In order to be able to more effectively achieve rapid charging, we must use advanced control methods. We have used a single-chip microcomputer to construct a battery charging real-time control system with automatic detection. According to the mechanism of rapid battery charging, the charged battery is dynamically detected in real time, depolarizing pulses are promptly issued and the charging current is adjusted, and charging is performed with a high charging average current, and the deposition of gas can be effectively suppressed. In order to achieve the purpose of rapid charging.
3. The composition of smart charging systemThe system is based on the AT89C2051 microcontroller, which is a high-performance 8-bit CMOS single-chip microcomputer. On-chip with 2K reprogrammable Flash EPROM, enough to store the general control program; has a wealth of I / O control; on-chip with two 16-bit timer / counter; multiple interrupt sources; a precision analog comparison Device. It provides a highly flexible and low-cost solution for many embedded control applications.
According to the needs of system functions, the composition of the hardware structure shown in Figure 1.
The system consists of several major parts:
(1) The AT89C2051 microcontroller is used as the control core of the entire smart charging system for data processing, calculation, and input and output control.
(2) Voltage detection circuit
The built-in integral analog comparator of RC circuit and AT89C2051 one-chip computer is used, it is used for the real-time detection of the battery voltage, this circuit will convert the detected analog voltage into the digital quantity and offer to the computer to deal with at the same time.
(3) Depolarization discharge circuit
It is composed of RC discharge circuit and MOSFET electronic switch. After the state of charge of the battery is processed by the single-chip microcomputer, the depolarization pulse is timely sent through the I/O port of AT89C2051 as required. The switch is closed and the discharge circuit is closed to eliminate the polarization of the battery. Phenomenon can also eliminate the bad memory of some batteries and increase its charge acceptance rate.
(4) Charge Control Circuit
High-frequency switching power supply with adjustable output voltage within a certain range. In addition, moderate current feedback is added to make the output characteristics soft, avoiding the current impact of the charger at the instant of loading, and having a constant current effect.
(5) Status display circuit
The state display circuit is composed of different indicators. According to different working states, the SCM controls the display of the charging or charging end state.
This system software is written using the MCS-51 assembly instructions and is solidified in the on-chip program memory, which is extremely convenient to use. The flow chart of the program is shown in Figure 2.
Dp Switcher,Hdmi Dp Switch,Dp Hdmi Switch,Switch Hdmi Dp
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