A quick charging method for a secondary battery and supercapacitor hybrid energy storage system

Abstract

The application provides a quick charging method for a secondary battery and super capacitor hybrid energy storage system. A secondary battery branch is formed by connecting a secondary battery and a milliohm resistor in series, a super capacitor is connected at both ends of the secondary battery branch, and a charging device is connected at both ends of the secondary battery branch away from the super capacitor; the charging device supplies power to the secondary battery and the super capacitor simultaneously in a constant current charging mode. The resistance value of the milliohm resistor is obtained through testing, the current passing through the secondary battery branch after connecting the resistor in series is smaller than the current passing through the super capacitor branch, the inconsistency of the charging rate of the secondary battery branch and the super capacitor branch is constructed, and the simultaneous charging of the secondary battery and the super capacitor can be realized. On the basis of the prior art, the charging speed is faster, the circuit design is simpler, and the effect is better.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of electronic technology, in particular to a kind of secondary battery and supercapacitor hybrid energy storage system fast charging method. BACKGROUND

[0002] In recent years, with the continuous development of new energy electric vehicles, single secondary battery as energy storage system cannot meet the demand more and more, supercapacitor with high power density is paid more and more attention, in order to integrate the advantages of secondary battery and supercapacitor, hybrid energy storage system composed of secondary battery and supercapacitor is widely concerned by people.At present, there are many researches on the fast charging method of secondary battery, such as pulse charging method, variable current intermittent charging method, reflex fast charging method, variable voltage intermittent charging method and so on, but there are few researches on the fast charging method of hybrid energy storage system.For example, the patent with the publication number "CN104393356A" points out that the charging sequence of lead-acid battery and supercapacitor is to charge the battery first and then charge the supercapacitor;The charging process of battery is divided into three stages, the first stage is variable average current intermittent charging based on pulse density modulation, the second stage is positive and negative pulse intermittent charging based on pulse density modulation, and the third stage is constant voltage trickle intermittent charging based on single pulse.At the beginning of the second stage of battery charging, the supercapacitor is charged, and the supercapacitor charging is divided into two stages, the first stage is to absorb the electric energy emitted by the battery during the second stage of its charging process, and the second stage is to start constant current charging of supercapacitor based on variable current during the third stage of battery charging.

[0003] In the above system, the supercapacitor is charged only at the second stage of battery charging, and only the negative pulse charging of the second stage, which cannot charge too much electric quantity, and the real charging starts only at the third stage of battery charging, so the charging time is long.Compared with pulse charging, constant current charging with the same current is undoubtedly faster.And in the three stages of the above system, there are corresponding parameter values for comparison and calculation, and the calculation process is relatively complex.Furthermore, the above system cannot realize simultaneous charging of the two, and the overall charging time is long. SUMMARY

[0004] Therefore, the technical problem to be solved by the present application is to overcome the problems in the prior art that the battery and supercapacitor in the hybrid energy storage system cannot be charged simultaneously, the charging time is long and the circuit is complex.

[0005] To solve the above technical problems, the present application provides a kind of secondary battery and supercapacitor hybrid energy storage system fast charging method, comprising:

[0006] S1: a preset resistance of milliohm level resistor is connected in series with a secondary battery to form a secondary battery branch, and a super capacitor is connected across the secondary battery branch to form a hybrid energy storage system; wherein the charging and discharging cutoff voltage and the nominal capacity of the secondary battery and the super capacitor are consistent;

[0007] S2: a charging device is connected across the secondary battery branch away from the super capacitor;

[0008] S3: the charging device supplies power to the hybrid energy storage system in a constant current charging mode, and monitors the terminal voltage of the secondary battery and the super capacitor in real time, and the terminal voltage of the secondary battery reaching the charging cutoff voltage is taken as the charging termination voltage of the hybrid energy storage system;

[0009] S4: when the charging of the hybrid energy storage system is completed, it is judged whether the terminal voltage of the super capacitor is equal to the charging cutoff voltage of the secondary battery; if not, the resistance value of the milliohm level resistor is increased or decreased, and step S3 is returned to be executed until the terminal voltage of the super capacitor is equal to the charging cutoff voltage of the secondary battery, and the current resistance value of the milliohm level resistor is taken as the target resistance value.

[0010] In an embodiment of the present application, if not, the resistance value of the milliohm level resistor is increased or decreased includes:

[0011] If the terminal voltage of the super capacitor is less than the charging cutoff voltage of the secondary battery, the resistance value of the milliohm level resistor is increased by a fixed resistance value;

[0012] If the terminal voltage of the super capacitor is greater than the charging cutoff voltage of the secondary battery, the resistance value of the milliohm level resistor is decreased by a fixed resistance value.

[0013] In an embodiment of the present application, the fixed resistance value is any one of 5mΩ, 10mΩ, 15mΩ and 20mΩ.

[0014] In an embodiment of the present application, the milliohm level resistor is composed of one or more fixed resistance value resistors or adjustable resistance combinations.

[0015] In an embodiment of the present application, the secondary battery is any one or more of a lead-acid battery, a lithium ion battery, a nickel-cadmium battery or a nickel-hydrogen battery.

[0016] In an embodiment of the present application, the secondary battery is composed of a plurality of secondary sub-batteries in series and parallel combination.

[0017] In an embodiment of the present application, the super capacitor is composed of a plurality of super sub-capacitors in series and parallel combination.

[0018] In one embodiment of the present application, the charging device is any one of a charge-discharge tester, a charger or a charging pile.

[0019] The present application also provides a secondary battery and super capacitor hybrid energy storage system, comprising:

[0020] a milliohm resistor, the resistance of the milliohm resistor being such that the end voltage of the super capacitor of the hybrid energy storage system is equal to the charging cutoff voltage of the secondary battery at the end of charging;

[0021] The secondary battery and the milliohm resistor are connected in series to form a secondary battery branch.

[0022] The super capacitor is connected across the secondary battery branch, and the super capacitor has the same charging and discharging cutoff voltage and nominal capacity as the secondary battery.

[0023] The present application also provides a new energy electric vehicle comprising the secondary battery and super capacitor hybrid energy storage system according to claim 9.

[0024] The above technical solution of the present application has the following advantages over the prior art:

[0025] The secondary battery and super capacitor hybrid energy storage system and the fast charging method according to the present application use a milliohm resistor connected in series with the secondary battery to alleviate the polarization effect of the secondary battery and reduce the influence of contact resistance voltage division, so that the current passing through the secondary battery branch is smaller than the current passing through the super capacitor branch, thereby creating the inconsistency of the charging rate of the two branches. BRIEF DESCRIPTION OF DRAWINGS

[0026] In order to make the content of the present application easier to be clearly understood, the present application will be further described in detail below according to specific embodiments of the present application and in conjunction with the accompanying drawings, in which

[0027] Figure 1 is a structural schematic diagram of the secondary battery and super capacitor hybrid energy storage system according to the present application;

[0028] Figure 2 is a structural schematic diagram of the lithium ion battery and super capacitor hybrid energy storage system in a specific embodiment of the present application. DETAILED DESCRIPTION

[0029] The present application uses a milliohm resistor connected in series with the secondary battery to alleviate the polarization effect of the secondary battery and reduce the influence of contact resistance voltage division, so as to achieve the inconsistency of the charging rate of the two branches, thereby achieving fast charging and charging as much as possible.

[0030] The application will be further described below in conjunction with the accompanying drawings and specific embodiments so that those skilled in the art can better understand the application and implement it.

[0031] Embodiment 1

[0032] Referring to Figure 1 As shown in the figure, the application is to connect a secondary battery and a milliohm resistor in series to form a secondary battery branch, and connect a super capacitor at both ends of the secondary battery branch to form a hybrid energy storage system. Since the charging process of the super capacitor does not have a voltage platform period like the secondary battery, the overall charging process presents linearity, and the charging speed is relatively fast. Therefore, in order to ensure that as much electricity as possible is charged, the charging device needs to be connected at both ends of the secondary battery branch far from the super capacitor, and the branch is shunted to charge the super capacitor. Among them, the charging and discharging cut-off voltage of the secondary battery and the capacitor is consistent with the nominal capacity.

[0033] In this embodiment, the resistance value of the milliohm resistor needs to be determined in combination with the actual situation according to the internal resistance and contact resistance of the secondary battery and the super capacitor used. First, a milliohm resistor with a preset resistance value is connected in series. During the charging process of the hybrid energy storage system, the voltage at the end of the super capacitor is monitored in real time, and the end voltage of the secondary battery reaching the charging cut-off voltage is taken as the charging termination voltage of the hybrid energy storage system.

[0034] After the charging of the hybrid energy storage system is completed, it is judged whether the voltage at the end of the super capacitor is equal to the charging cut-off voltage of the secondary battery. If the voltage at the end of the super capacitor is less than the charging cut-off voltage of the secondary battery, the resistance value of the milliohm resistor is increased, and then tested again until the voltage at the end of the super capacitor is equal to the charging cut-off voltage of the secondary battery. If the voltage at the end of the super capacitor is greater than the charging cut-off voltage of the secondary battery, the resistance value of the milliohm resistor is decreased, and then tested again until the voltage at the end of the super capacitor is equal to the charging cut-off voltage of the secondary battery. The current resistance value of the milliohm resistor is set as the target resistance value.

[0035] In this embodiment, the resistance value of the fixed resistor can be increased or decreased by 5mΩ, 10mΩ, 15mΩ, 20mΩ, etc. It is not suitable to be too large, so as to prevent the damage of the super capacitor caused by the excessive voltage at the end of the super capacitor.

[0036] In this embodiment, since the constant current charging with the same current is faster than the pulse charging in the prior art, the charging device in the application supplies power to the hybrid energy storage system in the form of constant current charging, and monitors the voltage at the end of the super capacitor in real time. Because the overall charging curve of the super capacitor presents linearity and does not have a voltage platform period, in order to protect the super capacitor from overcharging and charge as much electricity as possible, the end voltage of the secondary battery reaching the charging cut-off voltage is taken as the charging termination voltage of the hybrid energy storage system.

[0037] In this embodiment, the milliohm level resistor can be composed of one or more fixed resistors, which can save costs in mass production, or it can be composed of one or more adjustable resistors, which can be directly adjusted when debugging the resistance value without reconnecting the resistor.

[0038] In this embodiment, the secondary battery is a lead-acid battery, a lithium-ion battery, a nickel-cadmium battery, or a nickel-metal hydride battery. One or more secondary batteries can be selected according to actual needs.

[0039] In this embodiment, the secondary battery can be composed of a single secondary battery or multiple secondary sub-batteries connected in series and parallel, which can be selected according to actual needs.

[0040] In this embodiment, the supercapacitor can be composed of a single supercapacitor or multiple supercapacitors connected in series and parallel, which can be selected according to actual needs.

[0041] Example 2

[0042] Reference Figure 2 This invention determines the target resistance value by continuously testing a preset resistance value. This method is applicable to all secondary batteries. Taking lithium-ion batteries as an example, this invention will specifically illustrate its advantages.

[0043] In this embodiment, for lithium-ion batteries and supercapacitors of the same capacity, the ohmic internal resistance of the lithium-ion battery is approximately three times that of the supercapacitor. Furthermore, the polarization effect of the lithium-ion battery is more pronounced during charging, resulting in a higher terminal voltage. Consequently, the contact resistance of the branch containing the supercapacitor is higher, while the contact resistance of the lithium-ion battery branch is lower. When the charging current is high, the voltage drop across the contact resistance is significant, leading to a lower terminal voltage for the supercapacitor. Therefore, to mitigate the polarization effect of the lithium-ion battery and reduce the impact of the voltage drop across the contact resistance, this invention achieves this by connecting a milliohm-level resistor in series with the lithium-ion battery branch.

[0044] In this embodiment, a lithium-ion battery is connected in series with a milliohm resistor to form a lithium-ion battery branch. A supercapacitor is connected to both ends of the lithium-ion battery branch. Since the supercapacitor does not have a voltage plateau period like the lithium-ion battery during charging, its charging process is linear and the charging speed is fast. Therefore, in order to ensure that as much power as possible can be charged, the charging clip of the charge-discharge tester is clamped to both ends of the lithium-ion battery branch, and the supercapacitor is charged by shunting the current through the branch.

[0045] In this embodiment, a milliohm-level resistor is connected in series in the lithium-ion battery branch. Resistors with different resistance values ​​can be connected in series for testing. During the test, the terminal voltages of the lithium-ion battery and the supercapacitor are monitored in real time. Without the resistor connected in series, the terminal voltage of the supercapacitor is always lower than that of the lithium-ion battery. After the resistor is connected in series, the terminal voltage of the supercapacitor continuously increases, which also means that the amount of charge is continuously increasing. Therefore, the resistance value corresponding to the supercapacitor terminal voltage being equal to the lithium-ion battery terminal voltage is taken as the optimal resistance value.

[0046] In this embodiment, the hybrid energy storage system is charged using a charge-discharge tester in a constant-current charging mode. During the charging process, the terminal voltages of the lithium-ion battery and the supercapacitor are monitored in real time to ensure that the supercapacitor's terminal voltage does not exceed the protection voltage. Because the supercapacitor's charging curve is generally linear and does not have a voltage plateau period, in order to ensure that the battery is not overcharged and to charge as much energy as possible, the charging termination signal of the hybrid energy storage system is used when the lithium-ion battery's terminal voltage reaches the charging cutoff voltage.

[0047] Example 3

[0048] In this embodiment, to achieve rapid charging of the hybrid energy storage system, it is necessary to increase the charging rate. At a high charging rate, a milliohm-level resistor is connected in series in the lithium-ion battery branch to maximize the current in the supercapacitor branch and minimize the current in the lithium-ion battery branch, while maintaining a constant total current. This alleviates the issue of artificially high terminal voltage caused by lithium-ion battery polarization, achieving rapid charging of the hybrid energy storage system while ensuring maximum charge input. Because constant current charging is faster, this invention employs a constant current charging method to achieve rapid charging.

[0049] In this embodiment, lithium-ion batteries and supercapacitors with nominal capacities of 4Ah and actual capacities of 3.97Ah and 4.35Ah, respectively, were tested. At room temperature of 25°C, the already discharged lithium-ion batteries and supercapacitors were first connected in parallel to form a hybrid energy storage system. Then, a 50mΩ resistor was connected in series in the lithium-ion battery branch. The charging clip of the charge / discharge tester was then clamped onto the lithium-ion battery branch, and the test was performed using a constant current charging method of 22A. To highlight the advantages of this invention, the test results were compared with those under the same operating conditions without a series resistor and with pulse charging (50% duty cycle, 10s period), which is currently popular in the fast charging field. The results are as follows:

[0050] With a 50mΩ resistor connected in series in the lithium-ion battery branch, the charging time is 0.346 hours, the total charged capacity is 7.608 Ah, and the overcapacity charging termination voltage is 4.22V. Without the resistor connected in series, the charging time is 0.233 hours, the total charged capacity is 5.125 Ah, and the overcapacity charging termination voltage is 3.671V. With pulse charging at a 50% duty cycle, the charging time is 0.523 hours, the total charged capacity is 5.829 Ah, and the overcapacity charging termination voltage is 3.829V. It can be seen that compared with constant current charging without the resistor connected in series, the charging time is only extended by 6.77 minutes when a 50mΩ resistor is connected in series, but the total charged capacity increases by 48.4%, reaching 91.4% of the actual capacity of the hybrid energy storage system. Compared with pulse charging at a 50% duty cycle, the charging time is shortened by 10.62 minutes, and the total charged capacity increases by 30.5%.

[0051] The comparison shows that connecting a resistor in series in the lithium-ion battery branch is superior to pulse charging in both shortening charging time and increasing the amount of charge. Compared with constant current charging without a resistor in series, the total amount of charge is significantly increased. This method is particularly advantageous when charging at high rates, making it suitable for fast charging scenarios, especially when charging at high rates.

[0052] This invention also provides a hybrid energy storage system combining a secondary battery and a supercapacitor, comprising:

[0053] A milliohm-level resistor is a resistor whose resistance value ensures that the voltage at the supercapacitor terminal of the hybrid energy storage system equals the charging cut-off voltage of the secondary battery at the end of charging. It is used to alleviate the polarization effect of the secondary battery and reduce the impact of contact resistance voltage division.

[0054] A secondary battery is connected in series with a milliohm-level resistor to form a secondary battery branch; a secondary battery can be composed of a single secondary sub-cell or multiple secondary sub-cells connected in series and parallel.

[0055] A supercapacitor is connected to both ends of a secondary battery branch. A supercapacitor can consist of a single supercapacitor or multiple supercapacitors connected in series and parallel. The supercapacitor has the same charge / discharge cutoff voltage and nominal capacity as the secondary battery.

[0056] The hybrid energy storage system of secondary battery and supercapacitor provided by this invention can be applied to fields such as new energy electric vehicles and rail power recovery.

[0057] Obviously, the above embodiments are merely illustrative examples for clear explanation and are not intended to limit the implementation. Those skilled in the art will recognize that other variations or modifications can be made based on the above description. It is neither necessary nor possible to exhaustively list all possible implementations here. However, obvious variations or modifications derived therefrom are still within the scope of protection of this invention.

Claims

1. A fast charging method for a hybrid energy storage system combining a secondary battery and a supercapacitor, characterized in that, include: S1: Connect a milliohm-level resistor with a preset resistance value in series with a secondary battery to form a secondary battery branch, and connect a supercapacitor to both ends of the secondary battery branch to form a hybrid energy storage system; wherein, the charging and discharging cutoff voltage and nominal capacity of the secondary battery and the supercapacitor are the same. S2: Connect the charging device to both ends of the secondary battery branch that is away from the supercapacitor; S3: The charging device supplies power to the hybrid energy storage system in a constant current charging mode, and monitors the terminal voltages of the secondary battery and the supercapacitor in real time. The charging termination voltage of the hybrid energy storage system is taken when the terminal voltage of the secondary battery reaches the charging cutoff voltage. S4: When the hybrid energy storage system finishes charging, determine whether the voltage at the supercapacitor terminal is equal to the charging cutoff voltage of the secondary battery; if not, increase or decrease the resistance value of the milliohm resistor, return to step S3, until the voltage at the supercapacitor terminal is equal to the charging cutoff voltage of the secondary battery, and set the current resistance value of the milliohm resistor as the target resistance value. If the value is not equal to the value of the milliohm resistor, increasing or decreasing the value of the milliohm resistor includes: If the terminal voltage of the supercapacitor is less than the charging cut-off voltage of the secondary battery, then the resistance value of the milliohm resistor is increased to a fixed value. If the terminal voltage of the supercapacitor is greater than the charging cut-off voltage of the secondary battery, the resistance value of the milliohm resistor is reduced to a fixed value. The fixed resistance value is any one of 5mΩ, 10mΩ, 15mΩ, and 20mΩ.

2. The fast charging method for a hybrid energy storage system combining a secondary battery and a supercapacitor as described in claim 1, characterized in that: The milliohm-level resistor is composed of one or more fixed-value resistors or adjustable resistors.

3. The fast charging method for a hybrid energy storage system combining a secondary battery and a supercapacitor as described in claim 1, characterized in that: The secondary battery is any one or more of lead-acid batteries, lithium-ion batteries, nickel-cadmium batteries, or nickel-metal hydride batteries.

4. The fast charging method for a hybrid energy storage system combining a secondary battery and a supercapacitor as described in claim 1, characterized in that: The secondary battery is composed of multiple secondary sub-batteries connected in series and parallel.

5. The fast charging method for a hybrid energy storage system combining a secondary battery and a supercapacitor as described in claim 1, characterized in that: The supercapacitor is composed of multiple supercapacitors connected in series and parallel.

6. The fast charging method for a hybrid energy storage system combining a secondary battery and a supercapacitor as described in claim 1, characterized in that: The charging equipment can be any one of a charge / discharge tester, a charger, or a charging pile.

7. A hybrid energy storage system combining a secondary battery and a supercapacitor, characterized in that, The system is charged using the fast charging method for a hybrid energy storage system of a secondary battery and a supercapacitor as described in any one of claims 1-6, wherein the hybrid energy storage system of the secondary battery and the supercapacitor comprises: A milliohm-level resistor, wherein the resistance value of the milliohm-level resistor is such that the voltage at the terminal of the supercapacitor in the hybrid energy storage system is equal to the charging cut-off voltage of the secondary battery at the end of charging. The secondary battery is connected in series with the milliohm resistor to form a secondary battery branch; The supercapacitor is connected to both ends of the secondary battery branch, and the supercapacitor has the same charge / discharge cutoff voltage and nominal capacity as the secondary battery.

8. A new energy electric vehicle, characterized in that, This includes the hybrid energy storage system of secondary battery and supercapacitor as described in claim 7.

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