Unmanned aerial vehicle lithium battery pack equalization parallel charging device and method, and battery maintenance method

Abstract

A kind of unmanned aerial vehicle lithium battery package equalization parallel charging device, charging method, battery maintenance method, including main controller, multiple sampling charging units, main controller is connected with multiple sampling charging units in parallel, each sampling charging unit is connected with a lithium battery in lithium battery package, sampling charging unit is used to charge lithium battery and regularly sample lithium battery voltage, main controller controls multiple lithium batteries in lithium battery package to carry out charging simultaneously by multiple parallel sampling charging units, the battery maintenance of the present application is realized by 3-5 times of charge-discharge cycle to lithium battery.The present application does not need battery management system to participate, directly charges lithium battery, can realize supervision and protection and equalization charging to lithium battery, the whole charging device structure is simple, the requirement of lithium battery is low, the weight of unmanned aerial vehicle battery caused by battery management system is reduced, the endurance of unmanned aerial vehicle can be greatly improved, so as to improve the market competitiveness of unmanned aerial vehicle.

Description

Technical Field

[0001] This invention belongs to the field of lithium battery charging technology, specifically relating to a balanced parallel charging device and method for a drone lithium battery pack. Background Technology

[0002] With the development of electronic and aerospace technologies, drone technology has developed rapidly, and its application areas have expanded from the military field to the civilian field, especially in agriculture, forestry, power, security and other civilian fields.

[0003] As drone applications become increasingly widespread, a wide variety of drone types have emerged on the market. Based on their flight principles, they can be mainly categorized into fixed-wing, helicopter, and multi-rotor drones. However, all these drones share a significant problem—limited flight time. The primary factor affecting flight time is the drone battery. Currently, drone batteries mainly use lithium batteries. To enhance battery efficiency, prevent overcharging and over-discharging, extend battery life, and monitor battery status, existing drone battery packs incorporate a battery management system. This inevitably increases the drone's weight, which in turn affects its performance. Countless manufacturers are racking their brains to improve the payload and flight time of their drones. Therefore, every inch and every gram of weight reduction is crucial to achieving longer flight times and the ability to carry more payload.

[0004] Currently, drone battery charging relies on a charger working in conjunction with the built-in battery management system of the drone's battery pack to monitor and protect the battery. Drone batteries are all lithium-ion batteries. Because lithium-ion batteries enter a dormant state after being stored for a period of time, their capacity is lower than normal. They need to be activated through normal charge and discharge cycles to restore their normal capacity. However, existing drone chargers can only charge and cannot discharge, thus failing to perform daily charge and discharge maintenance of lithium batteries.

[0005] Therefore, there is an urgent need for a charging method and device to simultaneously charge lithium batteries, monitor and protect the battery charging status, and perform daily charging and discharging maintenance of lithium batteries. This would eliminate the need for a battery management system in drone battery packs. Removing the battery management system from the drone battery pack would significantly reduce the weight of the drone, thereby greatly improving its range. Summary of the Invention

[0006] The technical problem to be solved by the present invention is to provide a drone lithium battery pack equalization parallel charging device and method that is reasonably designed, has low energy consumption, high accuracy, high efficiency, and realizes lithium battery charging and discharging maintenance.

[0007] The technical solution adopted to solve the above technical problems is: a parallel charging device for a drone lithium battery pack, including a main controller and multiple sampling charging units. Multiple sampling charging units are connected in parallel on the main controller. Each sampling charging unit is connected to a lithium battery in the lithium battery pack. The sampling charging unit is used to charge the lithium battery and sample the lithium battery voltage at regular intervals. The main controller controls multiple lithium batteries in the lithium battery pack to charge simultaneously through multiple parallel sampling charging units.

[0008] The sampling and charging unit includes a constant current source, a constant current source switch, a voltage sampling circuit, a load switch, and a discharge load. The constant current source is connected to the lithium battery and is used to charge the lithium battery. The constant current source switch is connected to the constant current source and the main controller and is used to control the constant current source to turn on or off. The voltage sampling circuit is connected to the main controller and is used to sample the lithium battery voltage at regular intervals. The discharge load is connected in parallel to the output terminal of the constant current source and is used to discharge the constant current source during voltage sampling or to discharge the lithium battery in battery maintenance mode. The load switch is connected to the discharge load and the main controller and is used to control the discharge load to turn on or off. The main controller controls the constant current source to turn on or off through the constant current source switch, controls the discharge load to turn on or off through the load switch, and samples the lithium battery voltage at regular intervals through the voltage sampling circuit.

[0009] As a preferred technical solution, the main controller is also connected to a touch screen, which is used to display the status parameters of the lithium battery in real time during the charging process and to set the operating mode of the lithium battery. The operating mode includes stop charging, start charging, and battery maintenance mode. The battery maintenance mode is to perform 3 to 5 charge-discharge cycles on the lithium battery.

[0010] As a preferred technical solution, the power of the discharge load is ≤0.1W.

[0011] The present invention also provides a charging method for a drone lithium battery pack equalization parallel charging device, comprising the following steps:

[0012] S1. Set the charging time T1 and sampling time T2 for each lithium battery.

[0013] First, power on the charging device, turn off all constant current sources, and sequentially sample the voltage of multiple lithium batteries through a multi-channel voltage sampling circuit. Based on the current voltage V0 of a single lithium battery sampled, set the charging time T1 and sampling time T2 for each lithium battery, with T2 being a fixed value.

[0014] S2. Turn on all constant current sources to charge. After charging a single lithium battery for time T1, the voltage sampling circuit starts sampling the lithium battery. At the same time, turn off the constant current source connected to the lithium battery, turn on the discharge load switch corresponding to the lithium battery, and discharge the output capacitor of the constant current source for time T3. T3 is a fixed value and T3 < T2. After the discharge is completed, turn off the discharge load switch. After sampling, if the sampled battery voltage is ≥ the battery full charge voltage, the lithium battery is fully charged and the constant current source is turned off. If the sampled battery voltage is < the battery full charge voltage, repeat this step until the lithium battery is fully charged.

[0015] S3. Once all lithium batteries are fully charged, turn off all constant current sources. Battery charging is complete.

[0016] As a preferred technical solution, the relationship between the charging time T1 and the current voltage V0 is as follows:

[0017]

[0018] In the formula, V m T1 represents the battery's full charge voltage, V0 represents the current voltage, C represents the lithium battery capacity, and I represents the constant charging current.

[0019] A charging method for a parallel charging device for a drone lithium battery pack, wherein the battery is fully charged with a voltage of 4.2V.

[0020] This invention also provides a battery maintenance method for a drone lithium battery pack equalization parallel charging device, characterized by comprising the following steps:

[0021] A1. Maintenance of a single lithium battery

[0022] a. Discharging a single lithium battery

[0023] The voltage of a single lithium battery is sampled in real time by a voltage sampling circuit. If the sampled voltage value of the single lithium battery is greater than the set minimum voltage value, the discharge load switch corresponding to the single lithium battery is turned on to discharge the single lithium battery until the sampled voltage value of the single lithium battery is equal to the set minimum voltage value. Then the discharge load switch corresponding to the single lithium battery is turned off, and the discharge of the single lithium battery is completed.

[0024] b. Charge a single lithium battery.

[0025] The constant current source of the single lithium battery is turned off, and the voltage of the single lithium battery is sampled by the voltage sampling circuit. Based on the current voltage V0 of the sampled single lithium battery, the charging time T1 and the sampling time T2 are set for the single lithium battery, and T2 is a fixed value.

[0026] The constant current source of the single lithium battery is turned on for charging. After charging the single lithium battery for time T1, the voltage sampling circuit starts sampling the single lithium battery. At the same time, the constant current source connected to the single lithium battery is turned off, and the discharge load switch corresponding to the single lithium battery is turned on to discharge the output capacitor of the constant current source. The discharge time is T3, which is a fixed value and T3 < T2. After the discharge is completed, the discharge load switch is turned off. After the sampling is completed, if the sampled battery voltage is ≥ the set maintenance voltage value, the voltage of the single lithium battery reaches the set maintenance voltage value, and the constant current source is turned off. If the sampled battery voltage is < the set maintenance voltage value, this step is repeated until the voltage of the single lithium battery reaches the set maintenance voltage value.

[0027] c. Repeat steps a and b 3 to 5 times to complete the maintenance of this single lithium battery;

[0028] A2. Maintenance of multiple lithium batteries within a lithium battery pack.

[0029] Perform step A1 simultaneously on multiple lithium batteries in the lithium battery pack until the voltage of all individual lithium batteries in the lithium battery pack is equal to the set maintenance voltage value. Then the maintenance of the lithium battery pack is complete.

[0030] As a preferred technical solution, the minimum voltage value is 2.95V to 3.05V; the maintenance voltage value is 3.8V to 3.9V.

[0031] The beneficial effects of this invention are as follows:

[0032] (1) This invention monitors the voltage status of the lithium battery at regular intervals through the voltage sampling circuit in the sampling charging unit and outputs it to the controller. The controller controls the constant current source to turn on or off according to the real-time voltage of the lithium battery. During the voltage sampling process, the constant current source is in the off state to ensure the accuracy of the sampling results, thereby achieving fast, accurate and balanced charging of the lithium battery. Compared with traditional drone lithium battery charging, it does not require the participation of the battery management system and can directly charge the lithium battery to achieve lithium battery supervision and protection. The entire charging device has a simple structure, low requirements for lithium batteries, reduces the weight of the drone battery caused by the battery management system, and can greatly improve the drone's endurance, thereby improving the drone's market competitiveness.

[0033] (2) This invention uses multiple sampling charging units to charge multiple lithium batteries in parallel, so as to turn off any battery that has reached a fully charged state at any time during the charging process without affecting the charging of other lithium batteries, thereby achieving the purpose of precise and balanced charging. Constant current source charging is used, the cable impedance has little impact, and the energy consumption is low.

[0034] (3) A discharge load is connected in parallel to the output terminal of the constant current source of the present invention. It is used to discharge the output capacitor of the constant current source during the sampling process to improve the sampling accuracy. It is also used to discharge the lithium battery in the maintenance mode to realize the daily maintenance of the lithium battery.

[0035] (4) Each sampling charging unit of the present invention is connected to a lithium battery in the lithium battery pack, which can realize the advantages of high working efficiency when other lithium batteries are being charged. Attached Figure Description

[0036] Figure 1 This is a schematic diagram of the structure of the drone lithium battery pack equalization parallel charging device in Embodiment 1 of the present invention.

[0037] Figure 2 This is a schematic diagram of the structure of the drone lithium battery pack equalization parallel charging device in Embodiment 2 of the present invention. Detailed Implementation

[0038] The present invention will be further described in detail below with reference to the accompanying drawings and embodiments, but the present invention is not limited to the following embodiments.

[0039] Example 1

[0040] This embodiment uses a lithium battery pack with 24 lithium batteries connected in series for charging as an example.

[0041] exist Figure 1 In this embodiment, the drone lithium battery pack equalization parallel charging device includes a main controller, sampling charging units, and a touch screen. The main controller has twenty-four sampling charging units connected in parallel. Each sampling charging unit is connected to one lithium battery in the lithium battery pack. The sampling charging units are used to charge the lithium batteries and periodically sample the lithium battery voltage. The main controller controls the twenty-four lithium batteries to charge simultaneously through the twenty-four parallel sampling charging units. The touch screen is connected to the main controller and is used to display the status parameters of the lithium batteries in real time during the charging process and to set the operating mode of the lithium batteries. The operating modes include stop charging, start charging, and battery maintenance mode. The battery maintenance mode involves performing 3 to 5 charge-discharge cycles on the lithium batteries to improve their service life.

[0042] The sampling and charging unit includes a constant current source, a constant current source switch, a voltage sampling circuit, a load switch, and a discharge load. The constant current source is connected to the lithium battery for charging. The constant current source switch is connected to both the constant current source and the main controller to control the constant current source's on / off state. The voltage sampling circuit is connected to the main controller to periodically sample the lithium battery voltage. The discharge load is connected in parallel to the output of the constant current source to discharge the constant current source's output capacitor during voltage sampling or to discharge the lithium battery in battery maintenance mode, enabling daily maintenance of the lithium battery. The discharge load's power is ≤0.1W to prevent incomplete charging. The load switch is connected to both the discharge load and the main controller to control the discharge load's on / off state. The main controller controls the constant current source's on / off state via the constant current source switch, controls the discharge load's on / off state via the load switch, and periodically samples the lithium battery voltage via the voltage sampling circuit.

[0043] The charging method of the drone lithium battery pack equalization parallel charging device in this embodiment includes the following steps:

[0044] S1. Set the charging time T1 and sampling time T2 for each lithium battery.

[0045] First, power on the charging device. The main controller controls all constant current source switches to turn off all constant current sources. The voltage of the twenty-four lithium batteries is sampled sequentially through the twenty-four voltage sampling circuits. Based on the current voltage V0 of the sampled individual lithium battery, the charging time T1 and sampling time T2 are set for each lithium battery, with T2 being 3s.

[0046] The relationship between charging time T1 and current voltage V0 is as follows:

[0047]

[0048] In the formula, V m To fully charge the battery, V m =4.2V, T1 is the charging battery compartment, V0 is the current voltage value, C is the total capacity of the lithium battery, I is the constant charging current, I = 8A;

[0049] S2. The main controller controls all constant current source switches to turn on all constant current sources for charging. After charging a single lithium battery for time T1, the voltage sampling circuit samples the lithium battery. At the same time, the main controller controls the constant current source switches to turn off the constant current source connected to the lithium battery and turns on the discharge load switch corresponding to the lithium battery to discharge the output capacitor of the constant current source. The discharge time is T3, which is 0.5s. After the discharge is completed, the main controller controls the load switch to turn off the discharge load. After sampling, if the sampled battery voltage is ≥ the full charge voltage of 4.2V, the lithium battery is fully charged. The main controller controls the constant current source switches to turn off the constant current source connected to the lithium battery. If the sampled battery voltage is < the full charge voltage of 4.2V, this step is repeated until the lithium battery is fully charged.

[0050] S3. Once all twenty-four lithium batteries are fully charged, turn off all constant current sources. The lithium battery pack charging is now complete.

[0051] Table 1 below shows the voltage data of the twenty-four lithium batteries in the lithium battery pack before charging and after equalization charging in this embodiment.

[0052] Table 1. Comparison of voltage values ​​of the twenty-four lithium batteries in the lithium battery pack before charging and after equalization charging.

[0053]

[0054] As shown in Table 1, the voltage data of the twenty-four lithium batteries in the lithium battery pack of this embodiment before charging shows that the voltages of the twenty-four lithium batteries have significant differences, with the highest voltage being 3.738V and the lowest being 3.707V. The voltage data of the twenty-four lithium batteries in the lithium battery pack of this embodiment after equalization charging by the present invention shows that the voltage values ​​of the twenty-four lithium batteries are basically equal to 4.2V, with an error range of 0 to 0.002V, indicating that the charging equalization effect of the present invention is good.

[0055] The battery maintenance method of the drone lithium battery pack equalization parallel charging device in this embodiment includes the following steps:

[0056] A1. Maintenance of a single lithium battery

[0057] a. Discharging a single lithium battery

[0058] The voltage of a single lithium battery is sampled in real time by a voltage sampling circuit. If the sampled voltage value of the single lithium battery is greater than the set minimum voltage value of 3V, it can also be 2.95V or 3.05V. Then the discharge load switch corresponding to the single lithium battery is turned on, and the discharge load discharges the single lithium battery until the sampled voltage value of the single lithium battery is equal to the set minimum voltage value. Then the discharge load switch corresponding to the single lithium battery is turned off, and the discharge of the single lithium battery is completed.

[0059] b. Charging a single lithium battery.

[0060] The constant current source of the single lithium battery is turned off, and the voltage of the single lithium battery is sampled by the voltage sampling circuit. Based on the current voltage V0 of the sampled single lithium battery, V0 = 3V, or it can be 2.95V or 3.05V, the charging time T1 and sampling time T2 are set for the single lithium battery, and T2 is 3s.

[0061] The relationship between charging time T1 and current voltage V0 is as follows:

[0062]

[0063] In the formula, V m To fully charge the battery, V m =4.2V, T1 is the charging battery compartment, V0 is the current voltage value, C is the total capacity of the lithium battery, I is the constant charging current, I = 8A;

[0064] The constant current source of the single lithium battery is turned on for charging. After charging for a time T1, the voltage sampling circuit starts sampling the voltage of the single lithium battery. At the same time, the constant current source connected to the single lithium battery is turned off, and the discharge load switch corresponding to the single lithium battery is turned on to discharge the output capacitor of the constant current source. The discharge time is T3, which is 0.5s. After the discharge is completed, the discharge load switch is turned off. After sampling, if the sampled battery voltage is ≥ the set maintenance voltage value of 3.85V, the single lithium battery is fully charged, and the constant current source is turned off. If the sampled battery voltage is < the set maintenance voltage value of 3.85V, this step is repeated until the lithium battery voltage is equal to the maintenance voltage value of 3.85V. The maintenance voltage value can also be 3.8V or 3.9V.

[0065] c. Repeat steps a and b 3 to 5 times to complete the maintenance of this single lithium battery;

[0066] A2. Maintenance of multiple lithium batteries within a lithium battery pack.

[0067] Perform step A1 simultaneously on multiple lithium batteries in the lithium battery pack until the voltage of all individual lithium batteries in the lithium battery pack is equal to the set maintenance voltage value. Then the maintenance of the lithium battery pack is complete.

[0068] The present invention features a parallel charging method, with each lithium battery corresponding to a sampling charging unit. This allows for the maintenance of other lithium batteries within the same lithium battery pack while one lithium battery is being charged, resulting in high working efficiency.

[0069] Example 2

[0070] The following example illustrates the charging process using a lithium battery pack containing seven lithium batteries connected in series.

[0071] exist Figure 2 In this embodiment, the drone lithium battery pack equalization parallel charging device includes a main controller, sampling charging units, and a touch screen. Seven sampling charging units are connected in parallel to the main controller. Each sampling charging unit is connected to one lithium battery in the lithium battery pack. The sampling charging units are used to charge the lithium batteries and periodically sample the lithium battery voltage. The main controller controls the seven lithium batteries to charge simultaneously through the seven parallel sampling charging units. The touch screen is connected to the main controller and is used to display the status parameters of the lithium batteries in real time during the charging process and to set the operating mode of the lithium batteries. The operating modes include stop charging, start charging, and battery maintenance mode. The battery maintenance mode involves performing 3 to 5 charge-discharge cycles on the lithium batteries to improve their service life.

[0072] The sampling and charging unit includes a constant current source, a constant current source switch, a voltage sampling circuit, a load switch, and a discharge load. The constant current source is connected to the lithium battery for charging. The constant current source switch is connected to both the constant current source and the main controller to control the constant current source's on / off state. The voltage sampling circuit is connected to the main controller to periodically sample the lithium battery voltage. The discharge load is connected in parallel to the output of the constant current source to discharge the constant current source's output capacitor during voltage sampling or to discharge the lithium battery in battery maintenance mode, enabling daily maintenance of the lithium battery. The discharge load's power is ≤0.1W to prevent incomplete charging. The load switch is connected to both the discharge load and the main controller to control the discharge load's on / off state. The main controller controls the constant current source's on / off state via the constant current source switch, controls the discharge load's on / off state via the load switch, and periodically samples the lithium battery voltage via the voltage sampling circuit.

[0073] The charging method of the drone lithium battery pack equalization parallel charging device in this embodiment includes the following steps:

[0074] S1. Set the charging time T1 and sampling time T2 for each lithium battery.

[0075] First, power on the charging device. The main controller controls the constant current source switch to turn off all constant current sources. The voltage of the seven lithium batteries is sampled sequentially through the seven-channel voltage sampling circuit. Based on the current voltage V0 of the sampled individual lithium battery, the charging time T1 and sampling time T2 are set for each lithium battery, with T2 being 3s.

[0076] The relationship between charging time T1 and current voltage V0 is as follows:

[0077]

[0078] In the formula, V m To fully charge the battery, Vm =4.2V, T1 is the charging battery compartment, V0 is the current voltage value, C is the total capacity of the lithium battery, I is the constant charging current, I = 8A;

[0079] S2. The main controller controls all constant current source switches to turn on all constant current sources for charging. After charging a single lithium battery for time T1, the voltage sampling circuit samples the lithium battery. At the same time, the main controller controls the constant current source switches to turn off the constant current source connected to the lithium battery and turns on the discharge load switch corresponding to the lithium battery to discharge the output capacitor of the constant current source. The discharge time is T3, which is 2 seconds. After the discharge is completed, the main controller controls the load switch to turn off the discharge load. After sampling time T2, if the sampled battery voltage is ≥ the full charge voltage of 4.2V, the lithium battery is fully charged. The main controller controls the constant current source switches to turn off the constant current source connected to the lithium battery. If the sampled battery voltage is < the full charge voltage of 4.2V, this step is repeated until the lithium battery is fully charged.

[0080] S3. Once all seven lithium batteries are fully charged, turn off all constant current sources. The lithium battery pack charging is now complete.

[0081] Table 2 below shows the voltage data of the seven lithium batteries in the lithium battery pack before charging and after equalization charging in this embodiment.

[0082] Table 2. Comparison of voltage values ​​of the seven lithium batteries in the lithium battery pack before charging and after equalization charging.

[0083]

[0084] As shown in Table 2, the voltage data of the seven lithium batteries in the lithium battery pack of this embodiment before charging shows that the voltages of the seven lithium batteries have significant differences, with the highest voltage being 3.724V and the lowest voltage being 3.701V. The voltage data of the seven lithium batteries in the lithium battery pack of this embodiment after equalization charging by the present invention shows that the voltage values ​​of the seven lithium batteries are basically equal to 4.2V, with an error range of 0 to 0.002V, indicating that the charging equalization effect of the present invention is good.

[0085] The battery maintenance method of the drone lithium battery pack equalization parallel charging device in this embodiment is the same as that in Embodiment 1.

Claims

1. A parallel charging device for equalizing lithium battery packs of unmanned aerial vehicles (UAVs), characterized in that, It includes a main controller and multiple sampling and charging units. The multiple sampling and charging units are connected in parallel to the main controller. Each sampling and charging unit is connected to one lithium battery in the lithium battery pack. The sampling and charging unit is used to charge the lithium battery and sample the voltage of the lithium battery at regular intervals. The main controller controls multiple lithium batteries in the lithium battery pack to charge simultaneously through multiple parallel-connected sampling and charging units; The sampling and charging unit includes a constant current source, a constant current source switch, a voltage sampling circuit, a load switch, and a discharge load; The constant current source is connected to the lithium battery and is used to charge the lithium battery; The constant current source switch is connected to the constant current source and the main controller and is used to control the opening or closing of the constant current source; The voltage sampling circuit is connected to the main controller and is used to sample the voltage of the lithium battery at regular intervals; The discharge load is connected in parallel to the output end of the constant current source and is used to discharge the constant current source during the voltage sampling process or discharge the lithium battery in the battery maintenance mode; The load switch is connected to the discharge load and the main controller and is used to control the opening or closing of the discharge load; The main controller controls the opening or closing of the constant current source through the constant current source switch, controls the opening or closing of the discharge load through the load switch, and samples the voltage of the lithium battery at regular intervals through the voltage sampling circuit; The charging method of the charging device includes the following steps: S1. Set the charging time T1 and sampling time T2 for each lithium battery. First, power on the charging device, turn off all constant current sources, and sample the voltages of multiple lithium batteries in sequence through the multi-channel voltage sampling circuit. Set the charging time T1 and sampling time T2 for each lithium battery according to the currently sampled voltage V0 of a single lithium battery. T2 is a fixed value; The relationship between the charging time T and the current voltage V0 is as follows: In the formula, V m The battery is fully charged at voltage, T1 is the charging time, V0 is the current voltage, C is the lithium battery capacity, and I is the constant charging current. S2. Turn on all constant current sources to charge. After a single lithium battery is charged for T1 time, the voltage sampling circuit starts to sample the voltage of this lithium battery. At the same time, turn off the constant current source connected to this lithium battery, turn on the discharge load switch corresponding to this lithium battery, and discharge the output capacitor of the constant current source. The discharge time is T3, and T3 is a fixed value, and T3 < T2. After the discharge ends, turn off the discharge load switch. After the sampling ends, if the sampled battery voltage ≥ the battery full voltage value, this lithium battery is full, turn off the constant current source. If the sampled battery voltage < the battery full voltage value, repeat this step until this lithium battery is full; S3. When multiple lithium batteries are fully charged, turn off all constant current sources, and the battery charging ends.

2. The drone lithium battery pack equalization parallel charging device according to claim 1, characterized in that, A touch screen is also connected to the main controller and is used to display the status parameters of the lithium battery in real time during the charging process and set the operation mode of the lithium battery. The operation mode includes stop charging, start charging, and battery maintenance mode. The battery maintenance mode is to perform 3 to 5 charge and discharge cycles on the lithium battery.

3. The drone lithium battery pack equalization parallel charging device according to claim 1, characterized in that, The power of the discharge load ≤ 0.1W.

4. The drone lithium battery pack equalization parallel charging device according to claim 1, characterized in that, The battery full voltage value is 4.2V.

5. A battery maintenance method for the equalization parallel charging device for a UAV lithium battery pack according to claim 2, characterized in that, It includes the following steps: A1. Maintain a single lithium battery a. Discharge a single lithium battery The voltage of a single lithium battery is sampled in real time by a voltage sampling circuit. If the sampled voltage value of the single lithium battery is greater than the set minimum voltage value, the discharge load switch corresponding to the single lithium battery is turned on, and the discharge load discharges the single lithium battery until the sampled voltage value of the single lithium battery is equal to the set minimum voltage value. Then the discharge load switch corresponding to the single lithium battery is turned off, and the discharge of the single lithium battery is completed. b. Charge a single lithium battery The constant current source of the single lithium battery is turned off, and the voltage of the single lithium battery is sampled by the voltage sampling circuit. Based on the current voltage V0 of the sampled single lithium battery, the charging time T1 and the sampling time T2 are set for the single lithium battery, and T2 is a fixed value. The constant current source of the single lithium battery is turned on for charging. After charging the single lithium battery for time T1, the voltage sampling circuit starts sampling the single lithium battery. At the same time, the constant current source connected to the single lithium battery is turned off, and the discharge load switch corresponding to the single lithium battery is turned on to discharge the output capacitor of the constant current source. The discharge time is T3, which is a fixed value and T3 < T2. After the discharge is completed, the discharge load switch is turned off. After the sampling is completed, if the sampled battery voltage is ≥ the set maintenance voltage value, the voltage of the single lithium battery reaches the set maintenance voltage value, and the constant current source is turned off. If the sampled battery voltage is < the set maintenance voltage value, this step is repeated until the voltage of the single lithium battery reaches the set maintenance voltage value. c. Repeat steps a and b 3 to 5 times to complete the maintenance of this single lithium battery; A2. Maintenance of multiple lithium batteries within a lithium battery pack Perform step A1 simultaneously on multiple lithium batteries in the lithium battery pack until the voltage of all individual lithium batteries in the lithium battery pack is equal to the set maintenance voltage value. Then the maintenance of the lithium battery pack is complete.

6. The battery maintenance method of the charging device according to claim 5, characterized in that, The minimum voltage value is 2.95V to 3.05V; the maintenance voltage value is 3.8V to 3.9V.

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