Quick charging method and charger for lead-acid storage battery

Abstract

The invention discloses a lead-acid storage battery rapid charging method and a charger, and relates to the technical field of battery charging, the method comprises the following steps: when the battery charging voltage is less than a second voltage, entering a variable current charging stage; entering a constant-voltage charging stage when the battery charging voltage is not smaller than the second voltage; when the constant-voltage charging stage stopping condition is met, entering a floating charging stage; when the preset charging duration of the floating charging stage is reached, the charging is ended; wherein the stopping condition of the constant-voltage charging stage is that the charging current of the constant-voltage charging stage is not greater than the lamp turning current, or the preset charging duration of the constant-voltage charging stage is reached. The charging method not only can meet the quick charging requirement of people, but also cannot influence the service life of the battery, and can reduce the heating value of the battery, thereby reducing the water loss of the battery.

Description

Technical Field

[0001] The invention relates to the technical field of battery charging, in particular to a lead-acid battery fast charging method and a charger. Background Art

[0002] Nowadays, more and more people choose electric two-wheelers for short-distance travel, and the charging method of electric two-wheelers is still the common three-stage charging, which has a slow charging rate and takes 8-12 hours to fully charge. However, as people's pace of life is getting faster and faster, the current charging method has caused trouble for fast-paced people, and more people hope to be able to charge their vehicles quickly and reduce the time required for charging.

[0003] However, most existing fast charging methods will cause the battery to heat up, thus affecting the battery life. Summary of the invention

[0004] In view of the above problems and technical requirements, the inventors have proposed a lead-acid battery fast charging method and charger, which can not only meet people's fast charging needs, but also will not affect the battery life. The technical solution of the present invention is as follows:

[0005] In a first aspect, the present application provides a method for fast charging a lead-acid battery, comprising the following steps:

[0006] When the battery charging voltage is less than the second voltage, the variable current charging stage is entered;

[0007] When the battery charging voltage is not less than the second voltage, entering the constant voltage charging stage;

[0008] When the stop conditions of the constant voltage charging stage are met, the floating charging stage begins;

[0009] When the preset charging time of the floating charging stage is reached, the charging ends;

[0010] The stopping condition of the constant voltage charging stage is that the charging current of the constant voltage charging stage is not greater than the lamp current, or the preset charging time of the constant voltage charging stage is reached.

[0011] A further technical solution is that, in the variable current charging stage, the method comprises:

[0012] Alternatingly charging the battery using a first charging current and a second charging current;

[0013] The first charging current is greater than the second charging current.

[0014] A further technical solution is to use a first charging current and a second charging current to charge the battery alternately, including:

[0015] When the internal ambient temperature of the charger is not higher than the first temperature, the first charging current and the second charging current are used to charge the battery alternately according to the respective set charging times, and the charging time of the first charging current is longer than the charging time of the second charging current, until the battery charging voltage rises to be greater than the first voltage;

[0016] When the internal ambient temperature of the charger is higher than the first temperature, the first charging current and the second charging current are switched according to the internal diode temperature of the charger to alternately charge the battery until the battery charging voltage rises to be greater than the first voltage;

[0017] The first voltage is smaller than the second voltage.

[0018] A further technical solution is to switch the first charging current and the second charging current to charge the battery alternately according to the temperature of the internal diode of the charger, including:

[0019] When the temperature of the internal diode of the charger is not higher than the second temperature, the first charging current is used to perform constant current charging on the battery;

[0020] When the temperature of the internal diode of the charger is higher than the second temperature, the second charging current is used to perform constant current charging on the battery;

[0021] The second temperature is higher than the first temperature.

[0022] A further technical solution is that, in the variable current charging stage, the method further comprises:

[0023] At the end of the alternating charging stage, the battery is charged with a third charging current at a constant current until the battery charging voltage rises to the second voltage;

[0024] The third charging current is between the first and second charging currents.

[0025] In a second aspect, the present application also provides a charger, which internally includes a rectifier filter circuit, a DCDC conversion circuit, a detection circuit and a control module;

[0026] After the charger is connected to the mains and the vehicle respectively, the AC mains is converted into a DC voltage through a rectifier filter circuit and a DCDC conversion circuit, which is used as the battery charging voltage to charge the vehicle battery;

[0027] The detection circuit is used to detect the battery charging voltage and current information;

[0028] The control module is used to read the battery charging voltage and current information, and according to the lead-acid battery fast charging method described in the first aspect, the charger is switched into different charging stages during the charging process.

[0029] Its further technical solution is that it also includes a temperature detection circuit based on thermistors. The thermistors are placed inside the charger and at the diodes inside the charger respectively, and are used to monitor the ambient temperature and diode temperature inside the charger and transmit them to the control module.

[0030] A further technical solution is that the control module includes an MCU, a main control unit, and a feedback unit located between the MCU output and the main control unit input;

[0031] A first MOS tube is provided in the DCDC conversion circuit, wherein the drain of the first MOS tube is connected to the opposite end of the primary winding of the transformer, the gate is connected to the output of the main control unit, and the source is grounded;

[0032] The MCU is used to read the battery charging voltage, the ambient temperature inside the charger, and the diode temperature, and compare them with the built-in voltage threshold and temperature threshold. It also feeds back the information required to enter different charging stages to the main control unit through the feedback unit.

[0033] The main control unit is used to adjust the PWM duty cycle of the charger by controlling the first MOS tube according to the information transmitted by the MCU, so as to output the battery charging voltage and charging current corresponding to different charging stages.

[0034] A further technical solution is that it also includes a fan speed regulation circuit inside, and the control module is connected to the control end of the fan speed regulation circuit to adjust the fan speed according to the internal diode temperature of the charger.

[0035] Its further technical solution is that it also includes a reverse control circuit connected in series between the detection circuit and the battery BMS, and the control module is connected to the control end of the reverse control circuit to disconnect the reverse control circuit when the polarity of the charger and the battery is reversed.

[0036] The beneficial technical effects of the present invention are:

[0037] This method can switch into different charging stages during the charging process. When the vehicle is charging at low power, the charging rate in the variable current charging stage is increased by about 20%, greatly shortening the total charging time and meeting the user's fast charging needs. In addition, at the alternating charging end in the variable current charging stage, derating charging is performed to reduce battery heating and water loss, thereby extending the battery life. The internal circuit of the charger integrated with this method is easy to implement and has a reasonable layout, which can meet the user's fast charging needs under low cost conditions. BRIEF DESCRIPTION OF THE DRAWINGS

[0038] Figure 1 It is a schematic diagram of the lead-acid battery fast charging method provided in the present application entering different charging stages.

[0039] Figure 2This is an overall flow chart of the lead-acid battery fast charging method provided in this application.

[0040] Figure 3 It is a schematic diagram of the battery charging voltage and charging current changing with time under charging mode 1 provided in the present application.

[0041] Figure 4 It is a schematic diagram of the battery charging voltage and charging current changing with time under charging mode 2 provided in the present application.

[0042] Figure 5 It is a schematic diagram of the internal circuit of the charger provided in this application. DETAILED DESCRIPTION

[0043] The specific implementation of the present invention will be further described below in conjunction with the accompanying drawings.

[0044] Please refer to Figure 1 As shown, an embodiment of the present application provides a method for fast charging a lead-acid battery, which specifically includes the following steps:

[0045] Step 1: When the battery charging voltage is less than the second voltage, the variable current charging stage is entered. In the variable current charging stage, the battery is charged alternately with the first charging current and the second charging current, and the first charging current is greater than the second charging current; the second voltage is usually between 14.3V and 15.1V.

[0046] Step 2: When the battery charging voltage is not less than the second voltage, the constant voltage charging stage is entered. In the constant voltage charging stage, since the voltage difference between the battery voltage and the battery charging voltage gradually decreases during the charging process, the charging current in this stage also decreases continuously.

[0047] Step 3: When the constant voltage charging stage stop condition is met, enter the floating charging stage (i.e. trickle charging). The constant voltage charging stage stop condition is that the charging current in the constant voltage charging stage is reduced to no more than the lamp current, or reaches the preset charging time of the constant voltage charging stage.

[0048] Step 4: When the preset charging time of the floating charge stage is reached, the charging is completed.

[0049] In step 1, the battery is charged alternately using a first charging current and a second charging current. Figure 2 Specifically shown is: a thermistor NTC1 for intelligent temperature sensing is placed inside the charger. After the charger is powered on and connected to the vehicle battery, NTC1 collects the internal ambient temperature of the charger. When the internal ambient temperature of the charger is not higher than a first temperature (such as 40°C), charging mode 1 is entered, otherwise charging mode 2 is entered.

[0050] Among them, the charging voltage and charging current in charging mode 1 change as follows: Figure 3 As shown, in this mode, the first charging current and the second charging current charge the battery alternately according to their respective set charging durations, and the charging duration of the first charging current is greater than the charging duration of the second charging current, until the battery charging voltage rises to a value greater than the first voltage. This stage is the alternating charging stage S1-1. Specifically, the MCU can be used to time the first charging current for timed charging. When the charging duration of the first charging current reaches the set time (such as 50 minutes), the second charging current is used for timed charging. When the charging duration of the second charging current reaches the set time (such as 5 minutes), it is switched back to the first charging current for timed charging. This switching is performed until the battery charging voltage rises to a value greater than the first voltage. The first voltage is usually 13.9V-14.1V and is less than the second voltage.

[0051] Among them, the charging voltage and charging current changes in charging mode 2 are as follows: Figure 4 As shown, a thermistor NTC2 for intelligent temperature sensing is arranged at the internal diode position of the charger. After the charger is powered on and connected to the vehicle battery, NTC1 collects the internal ambient temperature of the charger, and NTC2 collects the internal diode temperature of the charger. When the internal ambient temperature of the charger is higher than the first temperature, in this mode, the first charging current and the second charging current are switched according to the internal diode temperature of the charger to alternately charge the battery until the battery charging voltage rises to greater than the first voltage. This stage is the alternating charging stage S1-1. Specifically, when the internal diode temperature of the charger is not higher than the second temperature (such as 120°C), the first charging current is used to charge the battery with a constant current. Thereafter, the diode temperature continues to rise. When NTC2 feedbacks that the internal diode temperature of the charger is higher than the second temperature, the second charging current is used to charge the battery with a constant current, which can reduce the diode temperature rise. The first and second charging currents are switched in this way until the battery charging voltage rises to greater than the first voltage.

[0052] In this embodiment, the first charging current of the two charging modes is set to N times (preferably 2 times) the second charging current, so that when switching to the second charging current, the temperature rise of power devices such as MOS and diodes inside the charger during the charging stage using the first charging current can be reduced; in addition, charging with the second charging current can also ensure that the battery is charged with more capacity, avoiding the battery being charged with the first charging current all the time, converting electrical energy into heat energy, and causing energy loss.

[0053] Since the charging time and current value of the first charging current are greater than those of the second charging current, the first charging current has been switched to at the end of S1-1 of charging mode 1 or 2. At this time, the current has not decreased, resulting in a sharp rise in the internal temperature of the battery during the constant voltage charging stage, which is prone to battery bulging. To avoid battery bulging, the present application uses a third charging current to perform constant current charging on the battery during the variable current charging stage, that is, at the end of S1-1 of the two charging modes, when it is detected that the battery charging voltage is greater than the first voltage, until the battery charging voltage rises to the second voltage. This stage is the transition stage S1-2, as shown in FIG. Figure 3 , Figure 4 The third charging current is between the first and second charging currents, which can reduce the hydrogen evolution reaction of the negative plate of the battery, improve the charging efficiency, reduce the heat generation of the battery, and extend the battery life.

[0054] In step 2 to step 4, the battery charging voltage in the constant voltage charging stage S2 is usually constant between 14.3V and 15.1V, and the charging current in this stage is the fourth charging current and gradually decreases, such as Figure 3 , Figure 4 When the fourth charging current decreases to not more than the lamp current, or the charging time of S2 reaches 2.5h-3h, it enters the floating charging stage S3. The battery charging voltage of S3 is usually constant to 13.8V. The charging current of this stage is the fifth charging current, which is less than the fourth charging current and also gradually decreases, as shown in FIG. Figure 3 , Figure 4 When the charging time of S3 reaches 2.5h-3h, the charging is finished, and a small current floating charge is performed at this stage to ensure that the battery is fully charged.

[0055] In this embodiment, the first charging current is set to 8A, and the second charging current is set to 4A; the third charging current is the average of the first and second charging currents, which is 6A; the lamp current is 15% of the third charging current. Among them, the ratio of the charging time of the first charging current under charging mode 1 to the charging time of the second charging current can be adjusted according to the internal clock of the MCU, and the charging time of the first charging current under charging mode 2 and the charging time of the second charging current are determined according to the temperature of the diode collected by the internal heat dissipation of the charger. In summary, for lead-acid batteries with long charging time and fast charging under low voltage conditions, the method provided in the S1 stage of this application is used to speed up charging by about 20%, and the total charging time is shortened, which can meet the user's fast charging needs.

[0056] Based on the same inventive concept, another embodiment of the present application provides a charger, such as Figure 5As shown, it includes a rectifier filter circuit, a DCDC conversion circuit, a detection circuit, a temperature detection circuit, a fan speed control circuit, a reverse control circuit and a control module. The control module is connected to the control end of the fan speed control circuit and the reverse control circuit. After the charger AC is connected to the mains and the DC is connected to the vehicle, the charger starts to work. The AC mains is converted into a DC voltage through the rectifier filter circuit and the DCDC conversion circuit, and is used as the battery charging voltage through the battery BMS to charge the vehicle battery. The detection circuit is used to detect the battery charging voltage and current information. The battery BMS transmits the collected voltage and current information to the control module. The control module simultaneously reads the battery charging voltage and current information transmitted by the detection circuit, and according to the lead-acid battery fast charging method introduced above, the charger switches to different charging stages during the charging process to achieve fast charging of the lead-acid battery.

[0057] Among them, the temperature detection circuit includes an ambient temperature detection circuit and a diode temperature detection circuit, both of which are based on thermistor circuit structures. NTC1 is placed inside the charger, and the two resistors R10 and NTC1 divide the voltage to calculate the voltage at the TEMP point. NTC2 is placed at the internal diode of the charger, and the resistors R8, NTC2 and R9 divide the voltage to calculate the voltage at the TEMP_D point. The control module obtains the current temperature of NTC1 through the output voltage at the TEMP point, which is the internal ambient temperature of the charger; similarly, the current temperature of NTC2 is obtained through the output voltage at the TEMP_D point, which is the internal diode temperature of the charger.

[0058] Among them, the control module includes an MCU, a main control unit, and a feedback unit located between the MCU output and the main control unit input. The feedback unit is implemented based on an optocoupler and is used to isolate and transmit information. After the charger is powered on, the AC is converted into DC, and the VCC DC voltage is obtained through the auxiliary windings 6 and 8 of the transformer T1. The VCC DC voltage is converted into a 5V voltage that can be used for the MCU through the LDO circuit, and the MCU starts to work. The MCU reads the battery charging voltage, the ambient temperature inside the charger, and the diode temperature, and compares and calculates with the built-in voltage threshold and temperature threshold, and feeds back the information required to enter different charging stages to the main control unit through the feedback unit. A first MOS tube Q1 is provided in the DCDC conversion circuit, and the drain of Q1 is connected to the opposite end of the primary winding of the transformer T1, the gate is connected to the output of the main control unit, and the source is grounded. The main control unit is used to adjust the PWM duty cycle of the charger by controlling Q1 according to the information transmitted by the MCU, thereby outputting the battery charging voltage and charging current corresponding to different charging stages.

[0059] In combination with the lead-acid battery fast charging method introduced above, it can be known that the MCU internal calculation compares the current temperature of NTC1 with the first temperature (such as 40°C). When the internal ambient temperature of the charger is not higher than the first temperature, the MCU starts charging mode 1. In this mode, the MCU times the first and second charging currents according to the internal clock circuit, and feeds back the charging current information and timing information to the main control unit through the feedback unit; the main control unit adjusts the PWM wave through Q1 to output the first charging current. When the charging time of the first charging current has reached the set charging time, it starts to adjust the PWM wave and output the second charging current, thereby shortening the S1-1 charging time and achieving fast charging.

[0060] When the ambient temperature inside the charger is higher than the first temperature, the MCU starts charging mode 2, in which the MCU further compares the current temperature of NTC2 with the second temperature (such as 120°C). When the temperature of the internal diode of the charger is not higher than the second temperature, the first charging current information is fed back to the main control unit through the feedback unit, and the main control unit adjusts the PWM wave through Q1 to output the first charging current; when NTC2 feedbacks that the temperature of the internal diode of the charger is higher than the second temperature, the second charging current information is fed back to the main control unit through the feedback unit, and the main control unit adjusts the PWM wave through Q1 to output the second charging current. At the same time, the MCU controls the fan speed control circuit according to the temperature of the internal diode of the charger to adjust the speed of the internal fan of the charger, so as to achieve rapid cooling of the diode, thereby shortening the S1-1 charging time and achieving fast charging.

[0061] like Figure 5 As shown, one end of the fan in the fan speed control circuit is connected to the power supply VCC through a resistor R5, and the other end is respectively connected to the anode of the diode D5 and the drain of the third MOS tube Q3, the cathode of D5 is connected to the power supply VCC, and the gate of Q3 is connected to the MCU through a resistor R6 as the control end of the fan speed control circuit, and the source of Q3 is grounded. The principle of this circuit is to adjust the duty cycle by MCU and feedback to the fan speed control circuit to realize fan speed control, and the larger the duty cycle, the higher the average voltage output by the fan speed control circuit, and the faster the fan speed. Specifically, the MCU obtains the current temperature of NTC2 through the diode detection current. When the temperature of NTC2 is higher than the second temperature, the MCU adjusts the duty cycle to 100%, D5 is not turned on, the output voltage at both ends of the fan is VCC, and the fan rotates at full speed; when the temperature of NTC2 is not higher than the second temperature, the MCU adjusts the duty cycle to 90%, D5 is turned on, the output voltage at both ends of the fan is 0.9VCC, and the fan rotates at 0.9 times the full speed.

[0062] The reverse connection control circuit includes a diode D4 and a second MOS tube Q2, wherein the anode of D4 is connected to the detection circuit, the cathode of D4 is connected to the drain of Q2, the source of Q2 is connected to the battery BMS, and the gate of Q2 is connected to the MCU as the control end of the reverse connection control circuit. By connecting D4 and Q2 in series between the detection circuit and the battery BMS, the connection between the charger and the battery can be disconnected when the polarity of the charger and the battery is reversed by utilizing the unidirectional conductivity of the diode and the on and off characteristics of the MOS tube. Specifically, if the polarity of the charger DC terminal and the battery is correctly connected, feedback is given to the MCU to control Q2 to close and conduct, then D4 is turned on, and a path is formed between the charger and the battery; if the polarity of the charger DC terminal and the battery is reversed, feedback is given to the MCU that the battery voltage is high, and Q2 is controlled to form an open circuit, then D4 is also not turned on, and the charger and the battery are disconnected, thereby protecting the charger and the battery.

[0063] The above is only a preferred embodiment of the present application, and the present invention is not limited to the above embodiments. It is understood that other improvements and changes directly derived or associated by those skilled in the art without departing from the spirit and concept of the present invention should be considered to be included in the protection scope of the present invention.

Claims

1. A method for fast charging a lead-acid battery, characterized in that: The method comprises: When the battery charging voltage is less than the second voltage, the variable current charging stage is entered; When the battery charging voltage is not less than the second voltage, entering the constant voltage charging stage; When the stop conditions of the constant voltage charging stage are met, the floating charging stage begins; When the preset charging time of the floating charging stage is reached, the charging ends; The stopping condition of the constant voltage charging stage is that the charging current of the constant voltage charging stage is not greater than the lamp current, or the preset charging time of the constant voltage charging stage is reached.

2. The lead-acid battery fast charging method according to claim 1, characterized in that: In the variable current charging stage, the method includes: Alternatingly charging the battery using a first charging current and a second charging current; Wherein, the first charging current is greater than the second charging current.

3. The lead-acid battery fast charging method according to claim 2, characterized in that: The method of alternately charging the battery using the first charging current and the second charging current comprises: When the internal ambient temperature of the charger is not higher than a first temperature, the first charging current and the second charging current charge the battery alternately according to respective set charging times, and the charging time of the first charging current is longer than the charging time of the second charging current, until the charging voltage of the battery rises to be greater than the first voltage; When the internal ambient temperature of the charger is higher than a first temperature, switching the first charging current and the second charging current according to the internal diode temperature of the charger to alternately charge the battery until the battery charging voltage rises to be greater than the first voltage; Wherein, the first voltage is smaller than the second voltage.

4. The lead-acid battery fast charging method according to claim 3, characterized in that: The method of switching the first charging current and the second charging current to alternately charge the battery according to the temperature of the internal diode of the charger comprises: When the temperature of the internal diode of the charger is not higher than the second temperature, using the first charging current to perform constant current charging on the battery; When the temperature of the internal diode of the charger is higher than the second temperature, the second charging current is used to perform constant current charging on the battery; Wherein, the second temperature is higher than the first temperature.

5. The lead-acid battery fast charging method according to claim 2, characterized in that: In the variable current charging stage, the method further includes: At the end of the alternating charging stage, the battery is charged with a third charging current at a constant current until the charging voltage of the battery rises to the second voltage; Wherein, the third charging current is between the first and second charging currents.

6. A charger, characterized in that: The internal components include rectification and filtering circuit, DCDC conversion circuit, detection circuit and control module; After the charger is connected to the mains and the vehicle respectively, the AC mains is converted into a DC voltage through the rectification and filtering circuit and the DCDC conversion circuit, which is used as a battery charging voltage to charge the battery of the vehicle; The detection circuit is used to detect battery charging voltage and current information; The control module is used to read the battery charging voltage and current information, and according to the lead-acid battery fast charging method according to any one of claims 1-5, enables the charger to switch into different charging stages during the charging process.

7. The charger according to claim 6, characterized in that: The interior also includes a temperature detection circuit based on thermistors, which are placed inside the charger and at the diodes inside the charger respectively, for monitoring the ambient temperature and diode temperature inside the charger, and transmitting them to the control module.

8. The charger according to claim 7, characterized in that: The control module includes an MCU, a main control unit, and a feedback unit located between the MCU output and the main control unit input; The DCDC conversion circuit is provided with a first MOS tube, the drain of the first MOS tube is connected to the opposite end of the primary winding of the transformer, the gate is connected to the output of the main control unit, and the source is grounded; The MCU is used to read the battery charging voltage, the ambient temperature inside the charger and the diode temperature, perform comparison operations with the built-in voltage threshold and temperature threshold, and feed back the information required for entering different charging stages to the main control unit through the feedback unit; The main control unit is used to adjust the PWM duty cycle of the charger by controlling the first MOS tube according to the information transmitted by the MCU, so as to output the battery charging voltage and charging current corresponding to different charging stages.

9. The charger according to claim 7, characterized in that: The interior also includes a fan speed regulation circuit, and the control module is connected to the control end of the fan speed regulation circuit and is used to adjust the fan speed according to the internal diode temperature of the charger.

10. The charger according to claim 6, characterized in that: The interior also includes a reverse connection control circuit connected in series between the detection circuit and the battery BMS. The control module is connected to the control end of the reverse connection control circuit and is used to disconnect the reverse connection control circuit when the polarity of the charger and the battery is reversed.

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