Battery discharge control method and device

Abstract

The present invention relates to the field of battery recycling. In order to achieve rapid and safe discharge of batteries, a battery discharge control method is provided, including: 1. Setting a cut-off voltage, a cut-off current and a continuous discharge time; 2. When the voltage of the discharged battery is higher than a first voltage value, a first current control value is used for constant current discharge; when the voltage of the discharged battery is lower than the first voltage value but higher than a second voltage value, a constant resistance mode is used for discharge; when the voltage and current of the discharged battery both drop to or below the discharge cut-off condition, a third current control value is used for constant current discharge, and the discharge lasts for a discharge time Te to end the discharge. The battery discharge device includes: a control unit and a power unit, the control unit is connected to the discharge battery through the power unit, and the power unit includes an error comparator, an amplifier, a current sampling element and a MOS tube. The above method can achieve rapid and safe discharge of the battery.

Description

Technical Field

[0001] The present invention relates to the field of battery recycling, and in particular to a battery discharge control method and device. Background Art

[0002] The recycling and reuse of power lithium batteries requires discharge equipment to release residual energy and release as much electricity as possible to ensure that they will not catch fire or even explode during subsequent crushing or disassembly.

[0003] To adapt to large-scale production, it is hoped that the discharge process of lithium batteries will be both fast and safe. However, if the discharge current cannot be well controlled, the lithium battery may heat up, bulge, leak electrolyte, or even catch fire during the discharge process. Especially after the battery voltage drops to the platform voltage, high current discharge will cause the battery temperature to rise sharply, creating a safety hazard.

[0004] At present, the deep discharge of power lithium batteries generally uses power resistors as loads, and the control of discharge current is achieved by changing the number of parallel power resistors through large current switching elements. The current regulation in this way is discontinuous, and the current decreases as the battery voltage decreases during the discharge process, and constant current discharge cannot be achieved. Some technologies use chopping control switching elements to discharge in series with load resistors, and achieve the purpose of adjusting the effective value of the current by changing the duty cycle of the discharge current. However, since the load resistor cannot be changed continuously and sampling is difficult due to the intermittent actual discharge current, it is difficult to control the discharge current, and it is difficult to achieve continuous adjustment of the discharge current and large current constant current discharge in a wide voltage range. Some other discharge devices use junction devices such as IGBT as current control elements to construct a discharge circuit, but due to the inherent conduction junction voltage drop of junction devices, the battery can only be discharged to a residual voltage of about 2V, and deep discharge with a residual battery voltage below 0.5V or even below 0.3V cannot be achieved. Summary of the invention

[0005] In order to achieve rapid and safe discharge of a battery, the present application provides a battery discharge control method and device.

[0006] The technical solution adopted by the present invention to solve the above problems is:

[0007] A battery discharge control method, comprising:

[0008] Step 1: Set the discharge cut-off conditions, including the cut-off voltage U e , cut-off current I e And the continuous discharge time T e ;

[0009] Step 2: Detect the voltage and current of the battery to be discharged, adjust the discharge current control value, and discharge the battery in three stages using different control values:

[0010] The first discharge stage: when the voltage of the battery being discharged is higher than the first voltage value U1, the first current control value is used to perform constant current discharge on the battery being discharged;

[0011] The second discharge stage: when the voltage of the battery being discharged is lower than the first voltage value U1 but higher than the second voltage value U2, the battery being discharged is discharged in a constant resistance manner;

[0012] The third discharge stage: when the voltage and current of the discharged battery both drop to the discharge cut-off condition or below, the third current control value is used to perform constant current discharge on the discharged battery for the discharge time Te, and the discharge is terminated; the third current control value is less than the first current control value.

[0013] Furthermore, the first current control value=discharge current reference, and the discharge current reference=battery current rate×battery capacity.

[0014] Further, the third current control value=continuous discharge current ratio×discharge current reference, wherein the continuous discharge current ratio is a proportional value less than 100%.

[0015] Furthermore, the equivalent resistance value R used in the second stage = the first voltage value U1 / the current detection value I at the time of U1 f2 .

[0016] A battery discharge device comprises: a control unit and at least one power unit, wherein the control unit is connected to a discharge battery through the power unit, the power unit comprises an error comparator, an amplifier, a current sampling element and a MOS tube, the drain of the MOS tube is connected to a positive electrode of the discharge battery, the source of the MOS tube is connected to a negative electrode of the discharge battery through the current sampling element, the input end of the amplifier is connected to the source of the MOS tube, the output end of the amplifier is respectively connected to the control unit and the second input end of the error comparator, the first input end of the error comparator is connected to the control unit, and the output end of the error comparator is connected to the gate of the MOS tube.

[0017] Furthermore, the control unit includes a controller, a first analog-to-digital converter, a second analog-to-digital converter and a digital-to-analog converter, the controller is connected to the positive electrode of the discharge battery through the first analog-to-digital converter, the second analog-to-digital converter is connected to the output end of the amplifier, and the digital-to-analog converter is connected to the error comparator.

[0018] Furthermore, the current sampling element is specifically a resistor or a Hall element.

[0019] In order to facilitate heat dissipation, a heat sink is also included, and the heat sink is connected to the power unit.

[0020] In order to facilitate parameter setting, a human-machine interface is also included, and the human-machine interface is connected to the control unit.

[0021] Compared with the prior art, the present invention has the following beneficial effects: MOSFET is used as a discharge current control element and also as a power dissipation element, so that the discharge current is continuously adjustable, and a large current switching switch element with contacts is not required, so that deep discharge with a residual voltage of the battery lower than 0.3V can be achieved, and the adjustment of the discharge current is achieved by closed-loop control by a hardware circuit, with fast response and small error, and the discharge process is easy to be automatically controlled based on software, and various control modes such as constant current and constant resistance are implemented to achieve safe and fast automatic deep discharge of power lithium batteries. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 The flowchart of the battery discharge control method is as follows;

[0023] Figure 2 It is a schematic diagram of the battery discharge device structure;

[0024] Figure numerals: 200, host computer, 201, control unit, 202, power unit, 203, discharge battery, 211, controller, 212, first analog-to-digital converter, 213, digital-to-analog converter, 214, second analog-to-digital converter, 221, error comparator, 222, amplifier, 223, MOS tube, 224, current sampling element. DETAILED DESCRIPTION

[0025] In order to make the purpose, technical solution and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with the embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention.

[0026] like Figure 1 As shown, the battery discharge control method includes:

[0027] Step 1: Set the discharge cut-off conditions, including the cut-off voltage U e , cut-off current I e And the continuous discharge time T e ;

[0028] Step 2: Detect the voltage and current of the battery to be discharged, adjust the discharge current control value, and discharge the battery in three stages using different control values:

[0029] The first discharge stage: when the voltage of the battery being discharged is higher than the first voltage value U1, the first current control value is used to perform constant current discharge on the battery being discharged;

[0030] The second discharge stage: when the voltage of the battery being discharged is lower than the first voltage value U1 but higher than the second voltage value U2, the battery being discharged is discharged in a constant resistance manner;

[0031] The third discharge stage: when the voltage and current of the discharged battery both drop to the discharge cut-off condition or below, the third current control value is used to perform constant current discharge on the discharged battery for the discharge time Te, and the discharge is terminated; the third current control value is less than the first current control value.

[0032] In this embodiment, the first current control value = discharge current reference, the discharge current reference = battery current rate × battery capacity, the battery current rate and battery capacity can be set together when setting the discharge cut-off condition in step 1. The third current control value I c3 = continuous discharge current rate m × discharge current reference I b , where the continuous discharge current ratio m is a proportional value less than 100%. The equivalent resistance value R used in the second stage = the first voltage value U1 / the current detection value I at the time of U1 f2 , that is, the second current control value I c2 =Battery voltage detection value U f2 The values ​​of the first voltage value U1, the second voltage value U2 and the continuous discharge current rate m can be selected according to different types of batteries and are not limited here.

[0033] In the discharge control method of the present invention, in the first discharge stage, the internal resistance of the discharged battery is relatively small, and a larger current is used for constant current discharge, which can release more battery residual energy in a shorter time without causing the battery temperature to rise too high. In the second discharge stage when the internal resistance of the battery rises rapidly, constant resistance discharge is used, which effectively limits the current, making the current smaller and smaller, thereby preventing the battery temperature from continuing to rise rapidly, thereby improving safety. In the third discharge stage, the battery has little residual energy left, and a more appropriate current is used for constant current discharge, which can release the battery's residual energy faster, achieve deep discharge, and avoid battery electrolyte leakage as much as possible. The above three-stage control method can achieve the effect of quickly and safely releasing the residual energy of the lithium battery.

[0034] like Figure 2As shown, the battery discharge device includes: a control unit 201 and at least one power unit 202. When actually used, the discharge battery 203 is connected to the battery discharge device. At this time, the control unit 201 is connected to the discharge battery 203 through the power unit 202. The power unit 202 includes an error comparator 221, an amplifier 222, a current sampling element 224 and a MOS tube 223. The drain of the MOS tube 223 is connected to the positive electrode of the discharge battery 203, the source of the MOS tube 223 is connected to the negative electrode of the discharge battery 203 through the current sampling element 224, the input end of the amplifier 222 is connected to the source of the MOS tube 223, the output end of the amplifier 222 is respectively connected to the control unit 201 and the second input end of the error comparator 221, the first input end of the error comparator 221 is connected to the control unit 201, and the output end of the error comparator 221 is connected to the gate of the MOS tube 223.

[0035] The control unit 201 is used to store the parameters required for device control set by the user, run the discharge control program, detect the actual discharge current and voltage, and send a discharge current control signal. The error comparator compares the discharge current control signal from the control unit with the current sampling signal from the current sampling element amplified by the amplifier, outputs a control signal to the gate of the MOS tube, adjusts the discharge current until the error is zero, so that the actual discharge current is equal to the control value, and the closed-loop control of the discharge current is realized by the hardware circuit. During the discharge process, the MOS tube acts as a variable resistor, and the residual energy of the battery is converted into heat dissipation through the equivalent resistance of the MOS tube.

[0036] MOS tube is used as the discharge current control element and also as the power dissipation element, so that the discharge current can be continuously adjusted. No large current switching element with contacts is required, and deep discharge with a residual voltage of less than 0.3V can be achieved. The discharge current is regulated by closed-loop control of the hardware circuit, with fast response and small error. The discharge process is easy to be automatically controlled based on software, and various control methods such as constant current and constant resistance can be implemented.

[0037] Specifically, the control unit 201 includes a controller 211, a first analog-to-digital converter 212, a second analog-to-digital converter 214 and a digital-to-analog converter 213. The controller 211 is connected to the positive electrode of the discharge battery 203 through the first analog-to-digital converter 212, the second analog-to-digital converter 214 is connected to the output end of the amplifier 222, and the digital-to-analog converter 214 is connected to the error comparator 221.

[0038] The current sampling element may be a resistor, a Hall element or other elements with similar functions.

[0039] In order to facilitate the heat dissipation of the power unit, a radiator may be provided, and a fan may be configured to perform forced air cooling on the radiator.

[0040] Furthermore, a human-machine interface is included, and the human-machine interface is connected to the control unit. The parameters such as the capacity of the discharged battery, the current rate, the discharge cut-off voltage and cut-off current, the continuous discharge time, etc. required for the device control can be set through the human-machine interface, and the device status can also be displayed, such as connecting to a computer through the human-machine interface.

[0041] When a large discharge current is required, multiple power units connected in parallel can be used to discharge one battery at the same time, or multiple power units can be used to discharge multiple batteries at the same time.

Claims

1. A battery discharge control method, characterized in that: include: Step 1: Set the discharge cut-off conditions, including the cut-off voltage U e , cut-off current I e And the continuous discharge time T e ; Step 2: Detect the voltage and current of the battery to be discharged, adjust the discharge current control value, and discharge the battery in three stages using different control values: The first discharge stage: when the voltage of the battery being discharged is higher than the first voltage value U1, the first current control value is used to perform constant current discharge on the battery being discharged; The second discharging stage: when the voltage of the battery being discharged is lower than the first voltage value U1 but higher than the second voltage value U2, the battery being discharged is discharged in a constant resistance manner; The third discharge stage: when the voltage and current of the discharged battery both drop to the discharge cut-off condition or below, the third current control value is used to perform constant current discharge on the discharged battery for the discharge time Te, and the discharge is terminated; the third current control value is less than the first current control value.

2. The battery discharge control method according to claim 1, characterized in that: The first current control value=discharge current reference, and the discharge current reference=battery current rate×battery capacity.

3. The battery discharge control method according to claim 2, characterized in that: The third current control value=continuous discharge current ratio×discharge current reference, wherein the continuous discharge current ratio is a proportional value less than 100%.

4. The battery discharge control method according to any one of claims 1 to 3, characterized in that: The equivalent resistance value R used in the second stage = the first voltage value U1 / the current detection value I at the time of U1 f2 .

5. A battery discharge device, characterized in that include: A control unit and at least one power unit, wherein the control unit is connected to the discharge battery through the power unit, and the power unit comprises an error comparator, an amplifier, a current sampling element and a MOS tube, wherein the drain of the MOS tube is connected to the positive electrode of the discharge battery, the source of the MOS tube is connected to the negative electrode of the discharge battery through the current sampling element, the input end of the amplifier is connected to the source of the MOS tube, the output end of the amplifier is respectively connected to the control unit and the second input end of the error comparator, the first input end of the error comparator is connected to the control unit, and the output end of the error comparator is connected to the gate of the MOS tube.

6. The battery discharge device according to claim 5, characterized in that: The control unit includes a controller, a first analog-to-digital converter, a second analog-to-digital converter and a digital-to-analog converter. The controller is connected to the positive electrode of the discharge battery through the first analog-to-digital converter, the second analog-to-digital converter is connected to the output end of the amplifier, and the digital-to-analog converter is connected to the error comparator.

7. The battery discharge device according to claim 5, characterized in that: The current sampling element is specifically a resistor or a Hall element.

8. The battery discharge device according to claim 5, characterized in that: A heat sink is also included, and the heat sink is connected to the power unit.

9. The battery discharge device according to any one of claims 5 to 8, characterized in that: It also includes a human-machine interface, which is connected to the control unit.

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