A lithium-ion power battery pack charging and discharging active equalization method

Abstract

The application discloses a kind of lithium ion power battery pack charging and discharging active equalization methods, belong to battery charging and discharging field.First, construct voltage equalization circuit, connect battery monomer selection circuit, and complete active equalization circuit is formed by chargeable battery and monomer battery.Then voltage acquisition module is connected in parallel at the two ends of active equalization circuit, and upper limit and lower limit of equalization voltage are set.Voltage acquisition module collects the voltage of each battery monomer in real time, if the voltage of battery monomer h is higher than upper limit value or lower than lower limit value, carry out equalization charging or discharging mode, and set the direction of charging and discharging.According to the setting, battery monomer h is equalized charged or discharged.Finally, by controlling the MOS tube in active equalization circuit to generate excitation with different frequencies, constant voltage or constant current is formed, so that power battery monomer or battery is quickly and efficiently completed equalization, until charging is completed.The application can prolong the service life of lithium ion battery.

Description

TECHNICAL FIELD

[0001] The application belongs to the field of battery charging and discharging, and particularly relates to a lithium-ion power battery pack charging and discharging active balancing method. BACKGROUND

[0002] With the progress of society and the development of economy, in view of the demand for traffic convenience and ecological environment protection, popularization of electric vehicles is the general trend of future automobile development. As a device for storing energy, the power battery becomes the core and key part of the electric vehicle. The lithium-ion power battery has been widely used in electric vehicles due to its advantages of light weight, high energy density, low self-discharge rate, long cycle life, green environmental protection and no memory effect.

[0003] Due to the requirements of voltage level and power output, the electric vehicle generally uses a battery pack formed by a large number of single batteries through series and parallel connection as its power source. During use, due to the inconsistency between the single batteries, the difference caused by continuous charging and discharging cycles will accelerate the capacity attenuation of some single batteries. If the inconsistency is not eliminated by reasonable balancing means, the single batteries cannot be simultaneously charged to the rated capacity during the overall charging of the battery pack; the power of the single batteries cannot be simultaneously consumed during the overall discharging of the battery pack, resulting in waste of the energy of the battery pack. More seriously, there is a risk of overcharging of some single batteries, which reduces the use efficiency of the battery pack or even causes safety problems.

[0004] According to the different directions of the battery energy, the balancing technology can be divided into passive balancing technology and active balancing technology. The principle of the passive balancing technology is to consume the excess energy of a single battery with high voltage on the parallel resistor, so that the voltage of the battery is reduced to the same level as other batteries. This balancing method has low balancing efficiency and poor balancing effect, and will cause energy waste. At the same time, the resistor will inevitably heat up by consuming energy, which will bring new safety hazards, and a corresponding heat dissipation device must be designed, which will increase the design and manufacturing cost of the system. The active balancing technology can transfer the energy of the battery through energy storage elements or high-frequency converters, which is a true balancing and has more application value and research significance.

[0005] Most of the current active balancing technologies adopt capacitors, inductors, transformers and DC / DC converters, which cannot effectively cope with the constant current and constant voltage requirements in different stages of lithium-ion battery charging and discharging, and thus cannot effectively prolong the service life of the battery pack. SUMMARY

[0006] The present application adopts wireless power supply technology to solve the above problems, and provides a lithium ion power battery charging and discharging active balancing method.

[0007] The active balancing method has the following specific steps:

[0008] Step one, construct a voltage balancing circuit and connect a battery monomer selection circuit, and form a complete active balancing circuit with the rechargeable battery and the monomer battery.

[0009] N battery monomers are connected in series to form a power battery pack, and a relay is connected between every two battery monomers, and the battery monomer selection circuit is connected in parallel at both ends of the power battery pack and the voltage balancing circuit, and different battery monomers can be connected by controlling the on-off of the relay.

[0010] The voltage balancing circuit includes symmetrically arranged first and second voltage stabilizing circuits; the first voltage stabilizing circuit includes a first capacitor E, a MOS tube E, a freewheeling diode E, a resistor E, a second capacitor E, a diode E, a first coupling coil and a primary resonance network; and the second voltage stabilizing circuit includes a first capacitor F, a MOS tube F, a freewheeling diode F, a resistor F, a second capacitor F, a diode F, a second coupling coil and a secondary resonance network.

[0011] The input end of the first voltage stabilizing circuit is connected to the battery monomer selection circuit, and the output end is a first loop composed of the first capacitor E, the MOS tube E, the freewheeling diode E, the resistor E, the second capacitor E and the diode E, and the primary resonance network.

[0012] The input end of the first capacitor F of the second voltage stabilizing circuit is connected to the rechargeable battery, and the output end is a second loop composed of the first capacitor F, the MOS tube F, the freewheeling diode F, the resistor F, the second capacitor F and the diode F, and the secondary resonance network.

[0013] The first coupling coil, the second coupling coil, the primary resonance network and the secondary resonance network together form a wireless power supply module.

[0014] Step two, the voltage acquisition module is connected in parallel at both ends of the active balancing circuit, the average voltage Um of the battery monomer is calculated, and the upper limit Umax and the lower limit Umin of the balancing voltage are set.

[0015] The voltage acquisition module is connected in parallel across the power battery pack, and the average voltage Um is obtained by dividing the total voltage U of the entire power battery pack by the number N of battery monomers; the upper limit of the battery monomer equalization voltage is Umax, and Umax = Um*(1+20%); the lower limit is Umin, and Umin = Um*(1-20%).

[0016] Step three, the voltage acquisition module acquires the voltage of each battery monomer in real time, for a certain battery monomer h, judges whether the voltage of the battery monomer h is higher than the upper limit value Umax or lower than the lower limit value Umin, if yes, enters step four to perform equalization charging and discharging management on the battery monomer h; otherwise, enters step seven;

[0017] Step four, the battery monomer selection circuit selects the monomer battery h to be equalized in the charging or discharging mode, and sets the charging and discharging direction.

[0018] The relay in the battery monomer selection circuit is controlled to turn on and off the battery monomer h, and the commutating switch is controlled to commutate the voltage, so as to keep the voltage direction output by the voltage equalization circuit unchanged.

[0019] Step five, for the selected current battery monomer h, equalization charging or discharging is performed on the battery monomer h according to the set charging and discharging direction;

[0020] The charging process of the battery monomer h is as follows: the voltage of the battery monomer h is set to U0, and U0 is lower than the lower limit Umin of the average voltage of the power battery pack, then the second voltage stabilization circuit controls the MOS tube F to be cut off, and controls the conduction and cutoff time of the MOS tube F, so that the second loop generates an alternating voltage U2 in the coil of the secondary resonant network, the alternating voltage U2 is converted and loaded to the first voltage stabilization circuit, and due to the rectification effect of the diode E and the first capacitor E, the alternating voltage is converted into a direct current voltage Ud2, and the size of the voltage Ud2 is controlled by the duty cycle of the MOS tube F, when the voltage Ud2 is higher than the selected monomer battery h, then the voltage Ud2 is loaded to charge the monomer battery h.

[0021] The voltage acquisition module monitors the voltage of the selected monomer battery h in real time, and when the voltage of the monomer battery h reaches the average voltage Um, the MOS tube F is turned off, the relay is selected to be turned off, and the charging of the battery monomer h is completed.

[0022] The discharging process of the battery cell h is as follows: when the voltage of the battery cell h is U0' higher than the upper limit Umax of the battery cell equalization voltage, the first voltage stabilizing circuit controls the MOS tube E to be cut off, and controls the on-off time of the MOS tube E, so that the first loop generates an alternating voltage U1 in the primary coil. The alternating voltage U1 is converted and loaded to the second voltage stabilizing circuit, and due to the rectification of the diode F and the first capacitor F, the alternating voltage is converted into a direct current voltage Ud1, and the size of the voltage Ud1 is controlled by the duty cycle of the on-off of the MOS tube E. When the voltage Ud1 is higher than the chargeable battery D, the voltage Ud1 is loaded to the chargeable battery D, and the battery D is charged.

[0023] Step six, by controlling the MOS tube in the active equalization circuit to generate excitation with different frequencies, a constant voltage or constant current is formed, so that the power battery cell or the storage battery can quickly and efficiently complete equalization.

[0024] 1) Constant current output mode:

[0025] The output current is: Irrespective of the load, constant voltage output can be achieved.

[0026] ω0 is the working frequency of the S-S resonance topology structure, L1 is the first coupling coil, C1 is the resonance capacitor of the primary resonance network, L2 is the second coupling coil, C2 is the resonance capacitor of the secondary resonance network, M is the mutual inductance between the first coupling coil and the second coupling coil, and V1 is the input voltage of the first coupling coil.

[0027] 2) Constant voltage output mode:

[0028] The output voltage of the first coupling coil is:

[0029] The output voltage of the second coupling coil is:

[0030] When the working frequency is respectively: Irrespective of the load, constant voltage output can be achieved.

[0031] I1 is the input current of the first coupling coil, I2 is the output current of the second coupling coil, R L is the load resistance, and k is the coupling coefficient of the two coupling coils.

[0032] Step seven, judging whether the current battery cell is charged or not, if yes, ending; otherwise, selecting the next battery cell and returning to step two.

[0033] The advantages of the present application are:

[0034] 1) A lithium-ion power battery pack charging and discharging active balancing method, which realizes non-contact energy transmission by using a wireless power supply system, and realizes constant current and constant voltage mode switching work of the battery by controlling the frequency of the driving switch, thereby prolonging the service life of the lithium-ion battery.

[0035] 2) A lithium-ion power battery pack charging and discharging active balancing method, which is fast and efficient in the active balancing process and can effectively manage the charging and discharging state of the battery. BRIEF DESCRIPTION OF DRAWINGS

[0036] Figure 1 is a flowchart of the lithium-ion power battery charging and discharging active balancing method of the present application;

[0037] Figure 2 is a structure diagram of the active balancing circuit formed by constructing the voltage balancing circuit of the present application;

[0038] Figure 3 is an equivalent circuit diagram of the active balancing circuit of the present application when charging the battery monomer;

[0039] Figure 4 is an equivalent circuit diagram of the active balancing circuit of the present application when discharging the battery monomer;

[0040] Figure 5 is an equivalent circuit diagram of the resonant topology network in the wireless power supply module of the present application;

[0041] A-voltage acquisition module; B-battery monomer selection circuit; C-voltage balancing circuit; D-rechargeable battery; E-first voltage stabilizing circuit; F-second voltage stabilizing circuit; G-wireless power supply module; H-battery monomer; I-commutating switch;

[0042] 1-first capacitor E; 2-MOS tube E; 3-free-wheeling diode E; 4-resistor E; 5-second capacitor E; 6-diode E; 7-first capacitor F; 8-MOS tube F; 9-free-wheeling diode F; 10-resistor F; 11-second capacitor F; 12-diode F; 13-first coupling coil; 14-second coupling coil; 15-primary resonant network; 16-secondary resonant network; DETAILED DESCRIPTION

[0043] The present application will be described in detail below with reference to the accompanying drawings.

[0044] The present application provides a lithium-ion power battery pack charging and discharging active balancing method, as shown in Figure 1 the specific steps are as follows:

[0045] Step one, construct a voltage balancing circuit, and connect a battery monomer selection circuit, a rechargeable battery and a battery monomer to form a complete active balancing circuit;

[0046] As Figure 2 shown, the equalization circuit includes a voltage acquisition module A, a battery cell selection circuit B, a voltage equalization circuit C, a rechargeable battery D and a cell H.

[0047] N-section cell H in series to form a power battery pack; every two cells are connected between a relay; the voltage acquisition module A is connected in parallel across the power battery pack, controlled by the battery management system, responsible for real-time acquisition of the voltage of each cell.

[0048] The battery cell selection circuit B is composed of a series of relays and a reversing switch I, the relays are controlled by the battery management system to turn on and off, the reversing switch I is controlled by the battery management system to reverse, by controlling the on-off of the relays, the battery cell to be equalized is selected;

[0049] The voltage equalization circuit C and the rechargeable battery D are used for voltage equalization management of the selected battery cell.

[0050] The voltage equalization circuit C includes a first voltage stabilizing circuit E and a second voltage stabilizing circuit F arranged symmetrically;

[0051] The first voltage stabilizing circuit E includes a first capacitor E1, a MOS tube E2, a freewheeling diode E3, a resistor E4, a second capacitor E5, a diode E6, a first coupling coil 13 and a primary resonance network 15; the second voltage stabilizing circuit includes a first capacitor F7, a MOS tube F8, a freewheeling diode F9, a resistor F10, a second capacitor F11, a diode F12, a second coupling coil 14 and a secondary resonance network 16;

[0052] The input end of the first voltage stabilizing circuit E is connected to the battery cell selection circuit B, and the output end is the primary loop of the wireless power supply system; the input end of the second voltage stabilizing circuit F is connected to the rechargeable battery D, and the output end is the secondary loop of the wireless power supply system. When the equalization circuit is applied to a car, the rechargeable battery D is preferably a 24V DC battery.

[0053] The specific connection is as follows:

[0054] The first capacitor E1 of the first voltage stabilizing circuit is connected in parallel across the output of the battery cell selection circuit B; the resistor E4 and the second capacitor E5 are connected in parallel, then connected in series with the freewheeling diode E3, connected in parallel across the primary resonance network 15 and the first capacitor E1, and the circuit of the resistor E4 and the second capacitor E5 connected in parallel and then connected in series with the freewheeling diode E3 is connected between the parallel circuit of the first capacitor E1 and the parallel circuit composed of the MOS tube E2 and the diode E6. The first capacitor E1, the MOS tube E2, the freewheeling diode E3, the resistor E4, the second capacitor E5 and the diode E6, together with the primary resonance network 15, form a first loop; the first coupling coil 13 is connected in parallel across the primary resonance network 15.

[0055] The first coupling coil 13 is paired with the second coupling coil 14 of the second voltage stabilizing circuit, and the second coupling coil 14 has a secondary resonance network 16 connected in parallel across the two ends of the second coupling coil 14; meanwhile, a circuit composed of a MOS tube F8 and a diode F12 connected in series is connected in parallel across the two ends of a first capacitor F7 of the second voltage stabilizing circuit; a rechargeable storage battery D is also connected in parallel across the two ends of the first capacitor F7. The first capacitor F7, the MOS tube F8, the freewheeling diode F9, the resistor F10, the second capacitor F11 and the diode F12 together with the secondary resonance network 16 form a second loop;

[0056] The paired first coupling coil 13 and the second coupling coil 14 and the parallel-connected primary resonance network 15 and the secondary resonance network 16 together form a wireless power supply module G.

[0057] Step two, the voltage collection module is connected in parallel across the two ends of the active balancing circuit, the average voltage Um of the battery monomer is calculated, and the upper limit Umax and the lower limit Umin of the balancing voltage are set.

[0058] The voltage collection module is connected in parallel across the two ends of the power battery pack, and the voltage of the battery monomer is collected in real time, and the collected voltage data is sent to the battery management system. The battery management system uses the total voltage U of the entire power battery pack to divide the number N of the battery monomers to obtain the average voltage Um of the battery monomers; the upper limit of the battery monomer balancing voltage is Umax, Umax=Um*(1+20%); and the lower limit is Umin, Umin=Um*(1-20%).

[0059] Step three, the voltage collection module collects the voltage of each battery monomer in real time, judges whether the voltage of a certain battery monomer h is higher than the upper limit value Umax or lower than the lower limit value Umin, if yes, enters step four to perform balancing charge and discharge management on the battery monomer h; otherwise, enters step seven;

[0060] Step four, the battery monomer selection circuit selects the monomer battery h to be balanced in the charging or discharging mode, and sets the charging and discharging direction.

[0061] The battery management system controls the on-off of the relay in the battery monomer selection circuit B to select the battery monomer h with voltage higher than the limit value Umax or lower than the limit value Umin, and controls the commutation switch E to commutate the voltage, so as to keep the direction of the voltage output by the voltage balancing circuit C unchanged.

[0062] Step five, for the selected current battery monomer h, the battery monomer h is balanced in the charging or discharging direction according to the set charging and discharging direction;

[0063] AsFigure 3 As shown, the battery monomer h charging process, specifically: set the voltage of the battery monomer h is U0, and U0 is lower than the average voltage of the lower limit of the power battery pack Umin, the battery management system control MOS tube F8 of the second voltage stabilizing circuit is cut off, and the on and off time of MOS tube F8 is controlled, so that the second loop generates alternating voltage U2 in the coil of the secondary resonant network 16, the alternating voltage U2 is converted and loaded to the first voltage stabilizing circuit, and due to the rectification effect of diode E6 and first capacitor E1, the alternating voltage is converted into direct current voltage Ud2, and the duty cycle control voltage Ud2 is controlled by the on-off of MOS tube F8, when the voltage Ud2 is higher than the selected monomer battery h, then Ud2 voltage is loaded to charge the monomer battery h.

[0064] The charging current of the monomer battery h can also be controlled by the duty cycle of the on-off of the MOS tube. The voltage acquisition module A monitors the voltage of the selected monomer battery h in real time, and when the voltage of the monomer battery h reaches the average voltage Um, the MOS tube F8 is turned off, and the relay in the battery monomer selection circuit B is turned off, and the charging of the battery monomer h is completed.

[0065] The discharging process of the battery monomer h is shown as follows: Figure 4 When the voltage of the battery monomer h is U0' higher than the upper limit of the battery monomer balancing voltage Umax, the first voltage stabilizing circuit controls the MOS tube E2 to be cut off, and the on and off time of the MOS tube E2 is controlled, so that the first loop generates alternating voltage U1 in the primary coil. The alternating voltage U1 is converted and loaded to the second voltage stabilizing circuit, and due to the rectification effect of diode F12 and capacitor F7, the alternating voltage is converted into direct current voltage Ud1, and the size of the voltage Ud1 is controlled by the duty cycle of the on-off of the MOS tube E2. When the voltage Ud1 is higher than the rechargeable battery D, then the voltage Ud1 is loaded to the rechargeable battery D, and the rechargeable battery D is charged.

[0066] The charging current of the rechargeable battery D can also be controlled by the duty cycle of the on-off of the MOS tube, and the voltage of the selected monomer battery h is monitored by the voltage acquisition module A in real time, and when the voltage of the monomer battery h reaches the average voltage Um, the relay is turned off, and the discharging of the battery monomer h is completed.

[0067] Step six, by controlling the MOS tube in the active balancing circuit to generate excitation with different frequencies, form a constant voltage or constant current, so that the power battery monomer or the rechargeable battery can complete the balancing quickly and efficiently.

[0068] To realize the function of voltage balance, the wireless power supply module needs to have completely consistent primary and secondary resonant networks, and the high-frequency conversion link uses MOS tubes to ensure the system's bidirectional controllability and the symmetry of the topology. Therefore, the resonant topology network that can be selected includes SS, PP, LCC-LCC, LCL-LCL, etc. The SS resonant topology network is preferred as the resonant topology module in the system.

[0069] Taking the SS resonant topology network as an example, the principle of realizing the constant current and constant voltage output function of the wireless power supply module is described, and the circuit principle diagram is as shown in Figure 5

[0070] 1) Constant current output mode:

[0071] When the working frequency of the system is: The output current of the first coupling coil is: which is independent of the load and can realize constant voltage output.

[0072] L1 is the first coupling coil, C1 is the resonant capacitor of the primary resonant network, L2 is the second coupling coil, C2 is the resonant capacitor of the secondary resonant network, M is the mutual inductance between the first coupling coil and the second coupling coil, and V1 is the input voltage of the first coupling coil.

[0073] 2) Constant voltage output mode:

[0074] When the working frequency is: The output voltage of the first coupling coil is:

[0075] The output voltage of the second coupling coil is: which is independent of the load and can realize constant voltage output.

[0076] I1 is the input current of the first coupling coil, I2 is the output current of the second coupling coil, R L is the load resistance, and k is the coupling coefficient of the two coupling coils.

[0077] By adjusting the frequency of the drive signal of the MOS tube, the constant current or constant voltage output of the wireless power supply system can be realized.

[0078] Step seven, judge whether the current battery monomer is fully charged, if yes, end; otherwise, select the next battery monomer and return to step two.

[0079] ​The application first judges the input and output direction of the battery monomer, then judges the constant current or constant voltage working mode, controls the MOS tube to generate excitation with different frequencies, generates the required induced voltage at the first or second voltage stabilizing circuit end, and realizes voltage stabilization, so that the power battery monomer or storage battery can quickly and efficiently complete equalization.

[0080] The input and output direction of the battery monomer is judged according to whether the whole power battery is in charging or discharging mode.

[0081] The constant current and constant voltage mode is judged according to the preset constant current and constant voltage coefficient, which is generally given by the battery manufacturer or vehicle-mounted BMS, and the realization of the constant current and constant voltage mode is determined according to the switching frequency of the circuit MOS.

Claims

1. A method for active balancing of charge and discharge of lithium-ion power battery pack, characterized in that, The specific steps are as follows: Step one, construct the voltage equalization circuit, and connect the battery monomer selection circuit, the rechargeable battery and the battery monomer form a complete active equalization circuit; N battery monomers are connected in series to form a power battery pack, a relay is connected between every two battery monomers, the battery monomer selection circuit is connected in parallel between the power battery pack and the voltage equalization circuit, and different battery monomers are connected by controlling the on-off of the relay; The voltage equalization circuit includes symmetrically arranged first and second voltage stabilizing circuits; the first voltage stabilizing circuit includes: a first capacitor E, a MOS tube E, a freewheeling diode E, a resistor E, a second capacitor E, a diode E, a first coupling coil and a primary resonance network; the second voltage stabilizing circuit includes: a first capacitor F, a MOS tube F, a freewheeling diode F, a resistor F, a second capacitor F, a diode F, a second coupling coil and a secondary resonance network; The input end of the first voltage stabilizing circuit is connected with the battery monomer selection circuit, and the output end is a first loop composed of the first capacitor E, the MOS tube E, the freewheeling diode E, the resistor E, the second capacitor E and the diode E, and the primary resonance network; the first coupling coil is connected in parallel between the two ends of the primary resonance network; The input end of the first capacitor F of the second voltage stabilizing circuit is connected with the rechargeable battery, and the output end is a second loop composed of the first capacitor F, the MOS tube F, the freewheeling diode F, the resistor F, the second capacitor F and the diode F, and the secondary resonance network; The first coupling coil, the second coupling coil, the primary resonance network and the secondary resonance network together form a wireless power supply module; Step two, the voltage collection module is connected in parallel between the two ends of the active equalization circuit, the average voltage Um of the battery monomers is calculated, and the upper limit Umax and the lower limit Umin of the equalization voltage are set; The voltage collection module is connected in parallel between the two ends of the power battery pack, the total voltage U of the entire power battery pack is used to obtain the average voltage Um by dividing the number N of the battery monomers; the upper limit of the battery monomer equalization voltage is Umax, Umax=Um*(1+20%); and the lower limit is Umin, Umin=Um*(1-20%); Step three, the voltage collection module collects the voltage of each battery monomer in real time, for a certain battery monomer h, it is judged whether the voltage of the battery monomer h is higher than the upper limit value Umax or lower than the lower limit value Umin, if yes, step four is entered to perform equalization charging and discharging management on the battery monomer h; otherwise, step seven is entered; Step four, the battery monomer selection circuit selects the monomer battery h to be equalized charged or discharged, and sets the charging and discharging direction; The relay in the battery monomer selection circuit is controlled to turn on and off the battery monomer h, and the commutating switch is controlled to commutate the voltage, so that the direction of the voltage output by the voltage equalization circuit is kept unchanged; Step five, for the selected current battery monomer h, equalization charging or discharging is performed on the battery monomer h according to the set charging and discharging direction; Step six, different excitations are generated by controlling the MOS tube in the active equalization circuit to form constant voltage or constant current, so that the power battery monomer or the rechargeable battery can quickly and efficiently complete equalization; 1) Constant current output mode: The output current is: The constant current output can be realized regardless of the load. ω0 is the operating frequency of the S-S resonant topology, L1 is the first coupling coil, C1 is the resonant capacitor of the primary resonant network, L2 is the second coupling coil, C2 is the resonant capacitor of the secondary resonant network, M is the mutual inductance between the first coupling coil and the second coupling coil, V1 is the input voltage of the first coupling coil; 2) Constant voltage output mode: The output voltage of the first coupling coil is: The output voltage of the second coupling coil is: When the working frequency is respectively: The constant voltage output can be realized regardless of the load. I1 is the input current of the first coupling coil, I2 is the output current of the second coupling coil, and k is the coupling coefficient of the two coupling coils; Step seven, judge whether the current battery monomer is charged, if yes, end; Otherwise, reselect the next battery monomer and return to step two.

2. The active charge-discharge equalization method for lithium-ion power battery pack according to claim 1, characterized in that, The step five is to charge the battery monomer h. The voltage of the battery monomer h is set as U0, and U0 is lower than the lower limit Umin of the average voltage of the power battery pack, then the second voltage stabilizing circuit controls the MOS tube F to be cut off, and controls the on-off time of the MOS tube F, so that the second loop generates an alternating voltage U2 in the coil of the secondary resonant network, the alternating voltage U2 is converted and loaded to the first voltage stabilizing circuit, due to the rectification effect of the diode E and the first capacitor E, the alternating voltage is converted into a direct current voltage Ud2, and the size of the voltage Ud2 is controlled by the duty cycle of the MOS tube F, when the voltage Ud2 is higher than the selected monomer battery h, then the voltage Ud2 is loaded to charge the monomer battery h; The voltage collection module monitors the voltage of the selected monomer battery h in real time, when the voltage of the monomer battery h reaches the average voltage Um, the MOS tube F is disconnected, the relay is selected to be disconnected, and the charging of the battery monomer h is completed. The discharging process of the battery monomer h is: when the voltage of the battery monomer h is U0' higher than the upper limit Umax of the battery monomer equalization voltage, the first voltage stabilizing circuit controls the MOS tube E to be cut off, and controls the on-off time of the MOS tube E, so that the first loop generates an alternating voltage U1 in the primary coil; The alternating voltage U1 is converted and loaded to the second voltage stabilizing circuit, due to the rectification effect of the diode F and the first capacitor F, the alternating voltage is converted into a direct current voltage Ud1, and the size of the voltage Ud1 is controlled by the duty cycle of the MOS tube E; When the voltage Ud1 is higher than the chargeable storage battery D, then the voltage Ud1 is loaded to the chargeable storage battery D, and the storage battery D is charged.

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