3.7v 3000mah 18650 battery

　　Intelligent rechargeable 3.7v 3000mah 18650 battery management mechanism

　　Lithium-ion 3.7v 3000mah 18650 battery is a new type of secondary 3.7v 3000mah 18650 battery developed in the 1990s. Because lithium-ion batteries have a series of advantages such as high energy density and long cycle life, they have quickly been widely used in portable electronic devices and have also been favored by lithium 3.7v 3000mah 18650 battery manufacturers.

　　Lithium-ion batteries are mainly composed of positive active materials, flammable organic electrolytes and carbon negative electrodes. Therefore, the safety of lithium-ion batteries is mainly caused by the chemical reactions between these components.

　　During use, according to the structural characteristics of the lithium 3.7v 3000mah 18650 battery, the maximum charge termination voltage should be lower than 4.2V, and it must not be overcharged, otherwise too much lithium ions from the positive electrode will be taken away, causing danger. Its charging and discharging requirements are relatively high, and a special constant current and constant voltage charger should generally be used for charging. Usually, after constant current charging reaches the set value, it switches to constant voltage charging. When constant voltage charging reaches below 0.1A, charging should be stopped.

　　The discharge of lithium batteries is due to the internal structure. During discharge, all lithium ions cannot move to the positive electrode. Some lithium ions must be retained at the negative electrode to ensure that lithium ions can be inserted into the channel smoothly during the next charge. Otherwise, the 3.7v 3000mah 18650 battery life will be shortened, so the discharge end voltage needs to be strictly controlled during discharge.

　　Therefore, designing a high-precision lithium-ion charging management system is crucial for lithium-ion 3.7v 3000mah 18650 battery applications. The intelligent lithium 3.7v 3000mah 18650 battery charging system introduced in this article is a high-end technical solution specially designed for lithium batteries. This system is suitable for real-time monitoring of lithium-ion/nickel metal hydride/lead-acid 3.7v 3000mah 18650 battery cells and entire groups, 3.7v 3000mah 18650 battery balancing, charge and discharge voltage, temperature monitoring, etc. It adopts intelligent technologies such as voltage balancing control and over-temperature protection, and is a powerful , Power 3.7v 3000mah 18650 battery charging management system with complete technical indicators.

　　2 System composition and design

　　The charging system is mainly composed of n (expandable) charging modules and upper PC computer monitoring software. Supports charging process programming, and can set working steps according to various working conditions such as constant current charging and constant voltage charging. In addition to hardware overvoltage and overcurrent protection, it also allows users to define overvoltage, overcurrent and other parameters for each channel. It has the functions of data collection, storage, communication and analysis, and has the function of power-down protection without losing data. In addition, a lithium 3.7v 3000mah 18650 battery management system is also configured, which is mainly composed of a charger, a main control unit, a data acquisition unit and a human-machine interface. The hardware block diagram is shown in Figure 1.

　　Figure 1 Block diagram of intelligent lithium 3.7v 3000mah 18650 battery charging system

　　3 Design of constant current and constant voltage source

　　The constant current and constant voltage source uses a switching power supply as the main circuit, which consists of an input electromagnetic interference filter (EMI), a rectifier filter circuit, a power conversion circuit, a pWM controller circuit, and an output rectifier filter circuit. Auxiliary circuits include input over-under voltage protection circuit, output over-under voltage protection circuit, output over-current protection circuit, output short-circuit protection circuit, etc.

　　The circuit block diagram of the switching power supply is shown in Figure 2.

　　Figure 2 Block diagram of switching power supply circuit

　　The lightning protection unit uses a varistor for protection. When there is a lightning strike, the high voltage generated is introduced into the power supply through the power grid. When the voltage at both ends of the varistor exceeds its working voltage, its resistance decreases, causing high-voltage energy to be consumed on the varistor.

　　The input filter circuit uses a double π filter network composed of inductors and capacitors to suppress electromagnetic noise and clutter signals from the input power supply, while also preventing high-frequency clutter generated by the power supply itself from interfering with the power grid.

　　The power conversion circuit uses the most widely used insulated gate field effect transistor MOSFET, which uses the acoustic and electrical effects on the semiconductor surface to work. Since its gate is in a non-conductive state, it can greatly increase the input resistance. MOS tubes use the gate-source voltage to change the amount of charge induced on the semiconductor surface, thereby controlling the drain current.

　　The main circuit adopts forward mode, and the control chip adopts UC3842 in current working mode. The circuit is shown in Figure 3. R4, C3, R5, R6, C4, D1, and D2 form a buffer and are connected in parallel with the switch MOS tube to reduce the voltage stress of the switch tube, reduce EMI, and prevent secondary breakdown. When the switch Q1 is turned off, the primary coil of the transformer is prone to generate peak voltages and peak currents. The combination of these components can absorb the peak voltages and currents well. The current peak signal measured from R3 participates in the duty cycle control of the current working cycle and is therefore the current limit of the current working cycle. When the voltage on R5 reaches 1V, UC3842 stops working and switch Q1 is turned off immediately. The junction capacitances CGS and CGD in R1 and Q1 together form an RC network. The charging and discharging of the capacitor directly affects the switching speed of the switching tube. If R1 is too small, it will easily cause oscillation and electromagnetic interference will be great; if R1 is too large, it will reduce the switching speed of the switch tube.

　　Z1 usually limits the GS voltage of the MOS tube below 18V, thereby protecting the MOS tube. The gate controlled voltage of Q1 is a saw-shaped wave. When the duty cycle is larger, the conduction time of Q1 is longer, and the energy stored in the transformer is more; when Q1 is turned off, the transformer passes through D1, D2, R5 , R4, and C3 release energy, and at the same time achieve the purpose of magnetic field reset, preparing the transformer for the next storage and transmission of energy. The IC constantly adjusts the duty cycle of the ⑥ pin saw-shaped wave according to the output voltage and current, thereby stabilizing the output current and voltage of the entire machine. C4 and R6 are spike voltage absorption circuits. The secondary side of T1 is a forward rectifier circuit.

　　Figure 3 Constant current and constant voltage source main circuit circuit diagram

　　4 Design of feedback loop

　　The feedback loop of the constant voltage type is composed of an op amp and an optocoupler as shown in Figure 4. When the output U0 rises, after being divided by the sampling resistors R7, R8, R10, and VR1, the U1③ pin voltage rises. When it exceeds the U1② pin reference voltage, the U1① pin outputs a high level, causing Q1 to conduct, and the optocoupler OT1 emits light. The diode emits light, the phototransistor is turned on, and the potential of UC3842 pin ① becomes low accordingly, thus changing the output duty cycle of pin U1 ⑥ and reducing U0. When the output U0 decreases, the U1③ pin voltage decreases. When it is lower than the U1② pin reference voltage, the U1① pin outputs a low level, Q1 does not conduct, the optocoupler OT1 light-emitting diode does not emit light, the phototransistor does not conduct, and the UC3842① pin potential rises. High, thereby changing the U1⑥ pin output duty cycle to increase and U0 to decrease. Repeatedly, the output voltage remains stable. Adjusting VR1 can change the output voltage value.

　　The constant current type is similar to the figure above. Just switch the ③ pin of the op amp to the current feedback through a relay.

　　Figure 4 Feedback loop schematic diagram

　　5 PC software design

　　Lithium 3.7v 3000mah 18650 battery charging software mainly consists of two independent software, namely charging control and charging data processing and analysis software. The charging control software is mainly responsible for monitoring and controlling the entire charging process of lithium batteries, and generating 3.7v 3000mah 18650 battery charging data files and recording charging data; the charging data processing and analysis software mainly realizes the functions of visual display, data processing and data analysis of charging data, and at the same time, according to the user It is required to provide the function of 3.7v 3000mah 18650 battery matching [5].

　　The two main system software, charging control and charging data processing and analysis software, are composed of respective functional modules. Among them, the charging control software includes functional modules such as charging process programming, security protection, process event logs, power-down protection recovery and data backup management, while the charging data processing and analysis software includes data processing, graphics processing, dynamic curves, data export and 3.7v 3000mah 18650 battery configuration. Group and other functional modules.

　　Charging process programming is the channel automatic charging process programming, which is the core part of channel charging. The charging process can be composed of many working steps, and different working modes and working parameters can be defined in each working step, such as constant current charging, constant voltage charging, etc. Of course, the charging step also includes parameters such as end conditions.

　　Security protection is a protective measure based on security needs. For a reasonable and normal charging process, these protection measures usually have no effect; however, since most charging processes take a long time, some unpredictable things may occur during this period (such as power outages, etc.), and users also Unreasonable main parameters may be set due to negligence or other reasons (such as unreasonable end conditions), or there may even be problems with the 3.7v 3000mah 18650 battery being tested.

　　Therefore it is necessary to set security protection parameters. During charging, once the "safety protection" conditions are met, charging will be stopped safely. After eliminating abnormal factors, users can still use the "continue start" function to resume charging.

　　During the 3.7v 3000mah 18650 battery charging process, if there is a power outage or power outage in the power supply system at any time, this charging system can protect on-site data to ensure that on-site data is not lost. After re-powering on, the charging system has a self-recovery function and can recover from the last time it was lost. Seamlessly connects to the power source and continues the charging process.

　　The data processing function module mainly implements the following functions:

　　1) Various viewing operations of data: including display/hide of data items, setting the display cycle range, folding and unfolding of each cycle, folding and unfolding of each process, etc.;

　　2) Copy data to WINDOWS clipboard: Mainly used to export specified data entries of an already opened data file to tool software such as EXCEL or WORD, or save as text format (.TXT);

　　3) View work information: View the channel information corresponding to the charging data and the set charging process and other information;

　　4) View charging events: View unexpected events that occur during channel charging (such as power outage, safety stop, etc.) or user's forced operations (such as forced jump, user stop);

　　5) Data printing and print preview: output data through the printer.

　　6 experiments

　　Connect the lines and power supply according to Figure 1, and conduct system experiments on power supply 1# and power supply 2#. First start the management system, start the charging and discharging device, and send charging instructions through the host computer. The tester records the actual charging current (voltage). Table 1 is the test data record form of 1# power supply and 2# power supply.

　　7 Conclusion

　　Through test verification, the charging and discharging device has reached the expected indicators, the 3.7v 3000mah 18650 battery management system is working normally and can meet the established functional requirements.

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