CN106992565A - A battery constant current discharge device - Google Patents

Abstract

The invention relates to a battery constant current discharge device, comprising: a resistance circuit and a control circuit; the resistance circuit includes: a PTC resistance, a resistance switch and a fan assembly; the fan assembly is suitable for controlling the discharge circuit connected to the battery The temperature of the PTC resistor; the control circuit includes: a current detection terminal, a resistance switch control terminal and a fan speed control terminal; the current detection terminal is suitable for detecting the discharge signal in the battery discharge circuit; the resistance switch control terminal adapted to output the first control signal of the resistance switch according to the discharge signal to control the on-off state of the resistance switch; the fan speed control terminal is adapted to output the second control signal of the fan assembly according to the discharge signal signal to control the speed of the fan assembly. The invention can realize constant current in the whole discharge process of the accumulator.

Description

A battery constant current discharge device

technical field

The invention relates to the field of storage battery circuits, in particular to a battery constant current discharge device.

Background technique

As we all know, after long-term operation of lead-acid batteries, active substances often fall off, electrolytes dry up, plate deformation, grid corrosion and vulcanization often occur, resulting in reduced battery capacity or even failure. Therefore, it is of great significance to check the battery capacity and prolong the service life of the lead-acid battery to conduct check discharge and activation discharge tests on the lead-acid battery at the right time. According to the maintenance requirements of the battery pack, when performing a check discharge on the battery, the battery must be discharged at a constant current according to the specified discharge rate.

At present, the common discharge devices in China are divided into the following two types:

(1) Fixed resistor discharge

As shown in Figure 1 is a schematic structural diagram of a battery fixed resistance discharge device, in which the fixed resistance discharge method uses a thermal resistor as a load, and consumes the battery electric energy in the form of heat energy to achieve the purpose of discharge. Cold and water-cooled. The principle includes controlling the discharge current by connecting different numbers of resistors R1, R2,..., Rn during discharge, and switches QF1, QF2,..., QFn are used to control the connection of resistors R1, R2,..., Rn respectively. However, this method has the following disadvantages: a) When the voltage of the battery pack decreases, the discharge current decreases correspondingly, and it is difficult to ensure constant current discharge; b) It is easily damaged, has a short service life and a large maintenance workload; c) It is greatly affected by the weather during operation , At the same time, due to the open flame, the safety is low; d) The volume is large.

(2) Constant current discharge method based on IGBT power electronics technology

As shown in Figure 2 is a schematic structural diagram of a battery constant current discharge device based on solid state relay technology. This method uses thermal resistance R1 as the load, and the load branch is connected in series with the IGBT power electronic tube G1. The control system is controlled by the IGBT drive circuit. IGBT on and off. When the IGBT tube G1 is turned on, the load R1 is connected to the main circuit; when the IGBT tube G1 is turned off, the load R1 is disconnected from the main circuit. The duty cycle of the PWM wave of the driving circuit is changed through the PWM control technology, and then the turn-on time of the IGBT is adjusted to ensure that the current of the whole system remains constant. This method has the following disadvantages: a) High-frequency harmonics will be generated at both ends of the battery during discharge, which will affect the power supply quality of the battery; Requirements; c) It needs to be connected to the mains for secondary power supply; d) At the same time, the volume of the device is relatively large.

Contents of the invention

The technical solution of the present invention provides a battery constant current discharge device, which can solve the problem in the prior art that the discharge current value cannot be kept constant during the battery discharge process.

In order to solve the above technical problems, the technical solution of the present invention provides a battery constant current discharge device, which is suitable for the battery discharge circuit, including: a resistance circuit and a control circuit;

The resistance circuit includes: a PTC resistance, a resistance switch and a fan assembly;

The resistance switch is adapted to connect the corresponding PTC resistor to the battery discharge circuit when it is closed and short-circuit the two ends of the corresponding PTC resistor when it is disconnected, and the fan assembly is suitable for controlling the The temperature of the PTC resistor;

The control circuit includes: a current detection terminal, a resistance switch control terminal and a fan speed control terminal;

The current detection terminal is suitable for detecting the discharge signal in the battery discharge circuit;

The resistance switch control terminal is adapted to output a first control signal of the resistance switch according to the discharge signal to control the on-off state of the resistance switch;

The fan speed control terminal is adapted to output a second control signal of the fan assembly according to the discharge signal to control the speed of the fan assembly.

Optionally, the storage battery includes a discharge terminal and a ground terminal, the resistance switch corresponds to a plurality of PTC resistors, one end of the PTC resistor is respectively connected to the discharge terminal, and the other end is respectively connected to the corresponding resistance switch.

Optionally, one end of the PTC resistor is connected to the discharge end through a selector switch, and the control circuit further includes: a selector switch control end, the selector switch control end is adapted to output a third control signal to Control the on-off state of the selector switch.

Optionally, the selection switch is a switch tube, and the switch tube includes a first input terminal, a first output terminal and a first control terminal; the first input terminal is connected to the discharge terminal, and the first output terminal is connected to the discharge terminal. Corresponding to the connection of the PTC resistor, the first control terminal is connected to the third control signal.

Optionally, the resistance switch is a solid-state relay, and the solid-state relay includes a second input terminal, a second output terminal, and a second control terminal; the second input terminals are respectively connected to the plurality of PTC resistors, and the The second output terminal is connected to the ground, and the second control terminal is connected to the first control signal.

Optionally, the control circuit further includes: a current sensor, an error amplifier, and a PI regulator;

The current sensor includes a current sensing input end and a current sensing output end, the current sensing input end is adapted to be connected to the discharge signal in the battery discharge circuit, and the current sensing output end is adapted to be connected to the current detection end;

The error amplifier includes: a positive input terminal, a negative input terminal and an error input terminal, and the PI regulator includes: an adjustment input terminal and an adjustment output terminal; the positive input terminal is connected to a reference signal, and the negative terminal The input end is connected to the current detection end, the adjustment input end is connected to the error input end, and the adjustment output end is connected to the fan speed control end.

Optionally, the control circuit further includes: a power controller, the adjustment output terminal is connected to the fan speed control terminal through the power controller.

Optionally, the fan assembly includes: a DC fan.

Optionally, the discharge signal is a discharge current, the first control signal is a control voltage, and the second control signal is a fan power supply voltage.

Optionally, the control circuit further includes: a drive circuit, the drive circuit includes a drive output terminal, and the drive output terminal is connected to the resistance switch control terminal;

The driving circuit is connected to an external selection button, and is adapted to judge the discharge signal at the position of the external selection button to output the first control signal at the driving output terminal.

The beneficial effects of the technical solution of the present invention at least include:

The technical solution of the present invention adopts the PTC resistor as the discharge load, which has excellent constant current discharge performance and adjustable heating power; during the discharge process, when the battery voltage drops, the technical solution of the present invention detects and adjusts the resistance circuit through the control circuit Fan components and resistance switches are used to adjust and adjust the power dissipation of the PTC resistance, so that the rate of drop is consistent with the rate of voltage drop, that is, the current during the entire discharge process can be kept constant, thereby solving the problem that the current value of the discharge current cannot be guaranteed during the discharge process of the prior art battery Constant question.

The technical solution of the invention is to control the discharge current, and a solid-state relay that can control the PTC resistance to be connected to the storage battery circuit is also provided, wherein the solid-state relay can control one PTC resistance, and can also control multiple PTC resistances. When different numbers of loads need to be connected, the control circuit can control the operation of the corresponding solid-state relay, and control the connection of the PTC resistor by closing the solid-state relay.

The technical solution of the present invention is also provided with a selection switch control terminal, which is arranged on each PTC resistance load branch and connected in series with each PTC resistance load branch. The control end of the selector switch can be a DC circuit breaker to protect the branch circuit from short circuit or overload.

When the battery constant current discharge device of the technical solution of the present invention is discharging, the control circuit can control different numbers of solid state relays to work, so that the corresponding PTC resistors of the solid state relays work, and convert electric energy into heat energy to discharge the battery at a constant current. At the same time, the control circuit adjusts the fan speed to change the air volume passing through the surface of the PTC resistor. During the discharge process, the control circuit detects the current, and adjusts the discharge current roughly by adjusting the opening and closing of the solid state relay, and finely adjusts the discharge current by controlling the fan speed. The combination of the two keeps the discharge current in the battery discharge circuit constant.

The technical solution of the present invention is based on the application of PTC resistors, and indirectly adjusts the fan air volume through PID control technology to make the discharge current of the battery constant; the technical solution of the present invention also uses a solid-state relay with short-circuit protection to control the loop access of the PTC resistors, which can realize discharge Constant current and adjustment of load resistance.

Description of drawings

The features, advantages and technical and industrial significance of exemplary embodiments of the invention will be described with reference to the accompanying drawings, in which like reference numerals refer to like elements, and in which:

Fig. 1 is a structural schematic diagram of a storage battery discharge device provided in the prior art;

Fig. 2 is a structural schematic diagram of another storage battery discharge device provided in the prior art;

Fig. 3-1 is the characteristic curve schematic diagram between a kind of temperature and the resistance value of the PTC resistance involved in the technical solution of the present invention;

Fig. 3-2 is the outline schematic diagram of the PTC resistor involved in the technical solution of the present invention;

Figure 3-3 is a schematic diagram of the constant current control of the battery constant current discharge device involved in the technical solution of the present invention;

Fig. 4 is a structural schematic diagram of the first battery constant current discharge device provided by the technical solution of the present invention;

Fig. 5 is a schematic structural view of the second battery constant current discharge device provided by the technical solution of the present invention;

Fig. 6 is a structural schematic diagram of a third battery constant current discharge device provided by the technical solution of the present invention;

Fig. 7 is a schematic structural diagram of a fourth battery constant current discharge device provided by the technical solution of the present invention;

Fig. 8 is a schematic structural diagram of a fifth battery constant current discharge device provided by the technical solution of the present invention;

Fig. 9 is a schematic structural diagram of the sixth battery constant current discharge device provided by the technical solution of the present invention;

Fig. 10 is a schematic structural diagram of the seventh battery constant current discharge device provided by the technical solution of the present invention;

Fig. 11 is a structural schematic diagram of an application example of a battery constant current discharge device provided by the technical solution of the present invention;

Fig. 12 is a structural schematic diagram of an application example of a control circuit in a battery constant current discharge device provided by the technical solution of the present invention.

detailed description

The traditional battery discharge device uses resistance wire as the discharge resistor. Since its resistance value is fixed, the discharge current decreases continuously with the voltage of the battery pack during the discharge process, and the current in the discharge process cannot be kept constant. The calculation of the capacity cannot be accurately reflected; during the discharge process, the resistance wire emits red light, and the safety factor is low.

PTC heating material is a new type of nonlinear resistance material. When it reaches the Curie point temperature, the resistance value increases sharply, and its temperature coefficient can reach 10-60%/℃ (positive temperature characteristic). Controlling the temperature can achieve the adjustment of the resistance (PTC effect). Figure 3-1 shows a characteristic curve of the resistance value and temperature of a PTC resistance. It can be seen that at the temperature Tmin, the minimum resistance value is Rmin, when the temperature is Tmax, its resistance value is the largest and reaches Rmin, and between the temperature Tc and Tp, its temperature basically rises in proportion.

The power dissipation of the PTC thermistor ceramic resistor is related to the ventilation volume of the radiator surface. By adjusting the ventilation volume of the radiator surface of the PTC thermistor ceramic resistor, the power dissipation of the PTC thermistor ceramic resistor and the battery voltage are kept at the same value. If the downward trend changes, the discharge current can always be kept constant, and the control of the ventilation volume can be adjusted by adjusting the speed of the DC fan, so the fan power supply that controls the fan speed can realize the constant discharge current of the battery.

The appearance of the PTC resistor used in the technical solution of the present invention is shown in Figure 3-2. Its upper end is two electrodes, which can be connected to the positive pole of direct current after short-circuiting, and the other end is a pole, which can be connected to the negative pole of direct current. The designed operating voltage can reach up to 600V (AC), and the power can reach 4.5kW.

Fig. 3-3 is a functional block diagram of the constant current discharge device for the battery constant current discharge of the technical solution of the present invention. It can be seen from the schematic block diagram that when the battery pack is discharged, the discharge current is set through the "constant current value selection knob", and the control circuit determines the discharge voltage level and discharge current by judging the position of the "constant current value selection button". The fixed discharge current reference is input to the non-inverting terminal of the error amplifier, and at the same time, the controller controls the corresponding number of corresponding solid state relay grid control electrode voltages to be set to high level and open to start discharging the battery pack. The current transformer connected in series in the discharge negative circuit of the battery pack converts the discharge current signal into a voltage signal and sends it to the inverting terminal of the error amplifier. After the difference between the current value detected by the current transformer and the constant current reference value is adjusted by PI, the voltage applied to the DC fan is controlled to change the speed of the DC fan; after the fan speed changes, the PTC thermistor ceramic resistor dissipates heat As the surface temperature of the device changes, the dissipation power of the PTC thermistor ceramic resistor also changes, and the discharge current also changes accordingly; when the discharge current is close to the set current, the output voltage of the fan power supply does not change, and the discharge current The current remains dynamically stable. The circuit breaker is used to protect the PTC resistor branch from short circuit or overload.

In order to better clearly express the technical solution of the present invention, the present invention will be further described below in conjunction with the accompanying drawings.

A battery constant current discharge device 1 shown in FIG. 4 is suitable for a battery discharge circuit and includes: a resistance circuit 10 and a control circuit 11 .

The resistor circuit 10 shown mainly includes a PTC resistor 100, a resistor switch 101 and a fan assembly 102 in the battery discharge circuit; the above devices constitute the discharge part of the battery discharge circuit.

Specifically, the resistance switch is adapted to connect the corresponding PTC resistor to the battery discharge circuit when it is closed, and short-circuit the two ends of the corresponding PTC resistor when it is turned off. In one example, the resistance switch is suitable for controlling a PTC resistance, and its control terminal is suitable for receiving a first control signal, and is opened and closed according to the first control information. If the resistance switch is closed, the corresponding connected PTC The resistance is connected to the battery discharge circuit, and the PTC resistance is used as the discharge load at this time; if the resistance switch is turned off, the corresponding PTC resistance is short-circuited, and the corresponding PTC resistance does not become a discharge load, but is short-circuited by the discharge circuit . In another example, the resistance switch is adapted to control a plurality of PTC resistances, and the plurality of PTC resistances controlled by each resistance switch are connected in parallel to the control loop, and the control terminal of the resistance switch is adapted to receive the first control signal, And disconnect and close according to the first control information, if the resistance switch is closed, the correspondingly connected PTC resistance is connected to the battery discharge circuit in parallel, and at this time the parallel PTC resistance is used as a discharge load; if the resistance switch is disconnected , then the corresponding parallel PTC resistors are short-circuited. At this time, the corresponding parallel-connected PTC resistors do not become discharge loads, but are short-circuited by the discharge circuit.

More specifically, the fan assembly is suitable for controlling the temperature of the PTC resistor connected to the battery discharge circuit. According to the technical principle of the technical solution of the present invention, the PTC resistor of the technical solution of the present invention is made of non-linear resistance material, and its specific resistance value can increase sharply with the increase of resistance temperature, and its temperature coefficient can reach 10-60 %/°C (positive temperature characteristic). The technical scheme of the invention can control the resistance value of the load connected to the discharge circuit by controlling the surface temperature of the PTC resistance. The technical scheme of the present invention utilizes the above-mentioned fan assembly to adjust the ventilation rate on the surface of the PTC resistor radiator, thereby keeping the power dissipation of the PTC resistor and the voltage of the storage battery changing according to the same downward trend, and achieving the purpose of maintaining a constant discharge current.

In one example, the air outlet of the fan assembly 102 is set facing the PTC resistor 100, the speed of the fan assembly 102 can be modulated according to the position of the air outlet and the required air volume, and the specific fan speed is determined by the second control signal control. In another example, there may be multiple fan assemblies 102, and one or more of the air outlets at different angles are set relative to the shown PTC resistor 100, and then according to the different positions of the air outlets of the fan assembly, the calculated The amount of air required, and the speed design of each fan, that is, the required speed of each fan is different, but the fan speed can be controlled by the second control signal.

Continuing to refer to FIG. 4 , the shown control circuit 11 mainly includes: a current detection terminal 111 , a resistance switch control terminal 112 and a fan speed control terminal 113 . Wherein, the current detection terminal 111 is suitable for detecting the discharge signal in the battery discharge circuit; the current detection terminal 111 can copy the discharge current in the battery discharge circuit through a structure such as a current mirror, and can also obtain the discharge signal through equal pressure point detection. The discharge voltage in the loop is used to detect the discharge signal.

More specifically, the resistance switch control terminal 112 is adapted to output a first control signal of the resistance switch according to the discharge signal to control the on-off state of the resistance switch. The set of first control signals may be a set of voltage or current signals each controlling the control terminal of the resistive switch 101 . In one example, the input of the discharge signal and the output of the first control signal are in a closed-loop control relationship, and the output of the first control signal can be regulated according to the control relationship between the load resistance of the PTC resistor and the discharge signal. There is a proportional relationship between the discharge signal and the resistance load in the battery discharge circuit, and the set of the first control signal is a set of control signals that control the opening and closing states of the resistance switch. value set, calculate the magnitude of the discharge signal corresponding to the resistance value in the corresponding resistance value set, and deduce the corresponding relationship between the signal value of the first control signal in the first control signal set and the discharge signal that can be generated. When the difference or the ratio of the difference between the actually detected discharge signal and the discharge signal corresponding to a certain first control signal is within a predetermined accuracy range, the resistance switch control terminal 112 outputs the first control signal. The above calculation process is realized in the control circuit 11 .

Similarly, the fan speed control terminal 113 is also adapted to output a second control signal of the fan assembly according to the discharge signal to control the speed of the fan assembly. On the premise that the fan assembly is a fan, the second control signal is a current or voltage signal for controlling the rotation speed of the fan. On the premise that the fan assembly is a plurality of fans, the set of second control signals is a set of current or voltage signals for controlling the rotation speed of the fans.

In one example, the input of the discharge signal and the output of the second control signal are also a closed-loop control relationship, and the surface temperature of the PTC resistor can be adjusted by controlling the fan speed to control the fan air volume according to the change characteristic function of the PTC resistor load resistance and temperature , so as to adjust the output of the second control signal based on the control relationship between the discharge signal and the fan speed.

According to different application scenarios, the manufacturer and change characteristic function of the PTC resistor are different, but the characteristic function is predetermined and does not belong to the solution scope limited by this embodiment. By counting the surface temperature of the PTC resistor under a specific current under different air volumes of the fan, the specific load resistance in the circuit can be obtained by controlling the air volume of the fan, so as to keep the discharge current in the circuit constant. The control circuit 11 can deduce the corresponding relationship between the signal value of the second control signal and the signal difference between the discharge signal and the specific current. When the actually detected discharge signal is the corresponding discharge signal, the control circuit 11 compares the discharge signal output the second control signal to adjust the air volume of the fan. The above calculation process is realized in the control circuit 11 .

More preferably, the fan in the fan assembly uses a DC fan. A preferred selection method of the corresponding signal source is that the discharge signal is a discharge current, the first control signal is a control voltage, and the second control signal is a power supply voltage of a fan fan. The selection method of the above signal source can be This simplifies the circuit and makes it easier to compare and output signals.

The PTC resistor in this embodiment may be a PTC thermistor ceramic resistor. The power dissipation of the PTC thermistor ceramic resistor is related to the ventilation volume of the radiator surface. By adjusting the ventilation volume of the radiator surface of the PTC thermistor ceramic resistor, the power dissipation of the PTC thermistor ceramic resistor and the battery voltage are kept at the same value. If the downward trend changes, the discharge current can always be kept constant, and the control of the ventilation volume can be adjusted by adjusting the speed of the DC fan. The control circuit can actually use the second control signal as a control through the output of the second control signal. The fan power supply of the fan speed, thereby realizing the constant discharge current of the battery.

It should be noted that, for a modification example of this embodiment, reference may be made to FIG. 5 , in which a battery constant current discharge device 2 is shown, including: a resistance circuit 20, a detection circuit 21, a first control circuit 22 and a first control circuit 22. Two control circuits 23 . The function and structure of the shown resistance circuit 20 are consistent with the resistance circuit 10 in FIG. Speed control end 231. The detection circuit 21 realizes the output of the discharge signal at the current detection terminal 211, the first control circuit 22 realizes the output of the first control signal at the resistance switch control terminal 221, and the second control circuit 23 realizes the output of the discharge signal at the fan speed The control terminal 231 outputs the second control signal, and the detection circuit 21, the first control circuit 22 and the second control circuit 23 respectively undertake the function of the control circuit 11 detecting the discharge signal in this embodiment, and generate the first discharge signal based on the discharge signal. The function of controlling the signal and the function of generating the second signal based on the discharge signal. The implementation of the technical solution of the present invention includes such a structural arrangement.

In another variation of this embodiment, the resistance switch corresponds to a plurality of PTC resistance settings. Referring to Fig. 6, a battery constant current discharge device 3 has multiple PTC resistors, including PTC resistors 1001, 1002, ..., 100n (n is a natural number greater than 2), and there are multiple resistor switches, including : resistance switches 1011, 1012, . . . , 101m (m is a natural number greater than 2), FIG. 6 is based on FIG. 4 . The storage battery involved includes a discharge terminal and a terminal to ground, and the resistance switch corresponds to a plurality of PTC resistances. One resistance switch corresponds to three PTC resistances. In other examples, it can be set as required: one resistance switch corresponds to two PTC resistances. PTC resistors, one resistor switch corresponds to four PTC resistors, etc. One end of the PTC resistor is respectively connected to the discharge end, and the other end is respectively connected to a corresponding resistance switch.

In an application example of this embodiment, the resistance switch is a solid state relay, and the solid state relay includes a second input terminal, a second output terminal and a second control terminal; the second input terminal is connected to the multiple A PTC resistance is connected, the second output terminal is connected to ground, and the second control terminal is connected to the first control signal; in the case of multiple resistance switches, the first control signal can be a parallel signal , each of which is suitable for controlling the control terminal of a resistive switch.

In another variation of this embodiment, as shown in Figure 7, a battery constant current discharge device 4, Figure 7 is based on Figure 6, wherein one end of the PTC resistors 1001, 1002, ..., 100n are respectively selected Switches 131, 132, ..., 13n are connected to the discharge end of the storage battery, and the control circuit 11 further includes: a selection switch control terminal 114, and the selection switch control terminal 114 is adapted to output a third control signal when the storage battery is discharging. Control the on-off state of the selector switch. Specifically, the selection switch can be a switch tube, and the switch tube includes a first input terminal, a first output terminal and a first control terminal; the first input terminal is connected to the discharge terminal, and the first output terminal is connected to the discharge terminal. Corresponding to the connection of the PTC resistor, the first control terminal is connected to the third control signal. In the technical solution of the present invention, the selection switch control terminal is arranged on each PTC resistance load branch and connected in series with each PTC resistance load branch. The control end of the selector switch can be a DC circuit breaker to protect the branch circuit from short circuit or overload. In the discharging state, the third control signal keeps the selection switch in the closed state.

In another variation of this embodiment, as shown in FIG. 8, a battery constant current discharge device 5 provides a specific implementation of the control circuit. FIG. 8 is based on FIG. 4, including: The resistance circuit 10 and the control circuit 11', wherein: the control circuit 11' includes: besides: the current detection terminal 111, the resistance switch control terminal 112 and the fan speed control terminal 113, it also includes: the current sensor 50, the error amplifier 51 and the PI adjustment Device 52.

The current sensor 50 includes: a current sensing input end 501 and a current sensing output end 502, the current sensing input end 501 is suitable for connecting to the discharge signal in the storage battery discharge circuit, and the current sensing output end 502 is suitable for connecting The current detection terminal 111.

The error amplifier 51 includes: a positive input terminal 511 , a negative input terminal 512 and an error output terminal 513 . The PI regulator 52 includes: an adjustment input 521 and an adjustment output 522; the positive input 511 is connected to a reference signal, the negative input 512 is connected to the current detection end 111, and the adjustment input The terminal 521 is connected to the error output terminal 513 , and the adjustment output terminal 522 is connected to the fan speed control terminal 113 .

In this example, the reference signal can be the specific current, that is, the current used for the aforementioned difference comparison with the discharge signal. Described PI regulator 52 is a kind of linear controller, and it forms control deviation according to described specific current and the discharge current that actual current sensor 50 detects output, and the proportion (P) and integral (I) of deviation constitute control by linear combination The control quantity is used to set the generation of the second control signal in the control circuit, so as to control the speed of the fan. The linear combination constitutes the control quantity by inputting the characteristic function between the indicated temperature and the resistance value of the PTC resistor and the current difference obtained by the control deviation, and evaluating the second control signal to be output. Due to the characteristic function between the indicated temperature and the resistance value of the known PTC resistance, the linear combination of the described PI regulator 52 can be set, if the requirement of the characteristic function is linear, the PTC resistance in Fig. 3 can be adopted A segment of the characteristic function that is linear in the characteristic curve function.

In another variation of this embodiment, as shown in FIG. 9, a battery constant current discharge device 6 provides another specific implementation of the control circuit. FIG. 9 is based on FIG. 8, wherein , the control circuit 11" also includes: a power controller 60, the adjustment output end 522 is connected to the fan speed control end 113 through the power controller 60, and the power controller 60 can adjust the output control amount of the output end 522 After power conversion, a voltage value that meets the fan control requirements is obtained, thereby smoothly controlling the fan assembly.

In another variation of this embodiment, as shown in FIG. 10, a battery constant current discharge device 7, FIG. ¹⁰ provides another specific implementation scheme of the control circuit 113 based on FIG. 4, The control circuit ¹¹³ further includes: a driving circuit 70 , the driving circuit 70 includes a driving output terminal 71 , and the driving output terminal 71 is connected to the resistance switch control terminal 112 . The driving circuit 71 is connected to an external selection button, and is adapted to determine the discharge signal at the position of the external selection button to output a driving control signal for controlling the resistance switch control terminal at the driving output terminal 71 . In fact, the battery constant current discharge device 7 shown in FIG. 10 provides a means for modulating the opening and closing of the resistance switch according to an external control signal.

According to the battery constant current discharge device 7 shown in FIG. 10 , the external selection button can be a "constant current value selection knob". When the battery pack is being discharged, the discharge current is set through the "constant current value selection knob", and the control circuit determines the discharge voltage level and discharge current by judging the position of the "constant current value selection button", sets the discharge current reference, and inputs to the non-inverting terminal of the error amplifier, and at the same time set the gate voltage of the corresponding solid state relay to a high level, and start to discharge the battery pack. The current transformer connected in series in the discharge negative circuit of the battery pack converts the discharge current signal into a voltage signal and sends it to the inverting terminal of the error amplifier. After the difference between the current value detected by the current transformer and the constant current reference value is adjusted by the PI controller, the voltage applied to the DC fan is controlled to change the speed of the DC fan; after the fan speed changes, the PTC thermal sensor The temperature on the surface of the ceramic resistor heat sink changes accordingly, the dissipation power of the PTC thermistor ceramic resistor also changes accordingly, and the discharge current also changes accordingly; when the discharge current is similar to the set current, the output voltage of the fan power supply does not change. At this time, the discharge current remains dynamic and stable.

Fig. 11 is the main circuit diagram of an application example of the battery pack constant current discharge device of the technical solution of the present invention, consisting of quick connectors, main circuit breakers (QF01, QF02), branch DC circuit breakers (QF1-1, QF1-2, QF1 -3, ..., QF26-1, QF26-2, QF26-3), PTC thermistor ceramic resistors (RT1-1, RT1-2, RT1-3, ..., RT26-1, RT26-2, RT26-3) And solid state relays (Q1, ..., Q13, Q4, ..., Q26) and other parts. Among them, the positive and negative cables of the battery pack are connected to the main positive and negative bus bars through quick connectors and main circuit breakers, and the main positive and negative bus bars are divided into left and right bus bars. The battery pack constant current discharge device is designed with 78 PTC thermistor ceramic resistors, which are divided into two rows, 39 in each row, installed on both sides of the discharge device respectively; the rated power of each PTC thermistor ceramic resistor is 4500W (wind speed is 4m /s). In order to control the discharge current, a solid state relay is set for every three PTC thermistor ceramic resistors. When different quantities of loads need to be connected, the corresponding solid state relay will work. Each load branch is connected in series with a DC circuit breaker to protect the branch from short circuit or overload. When discharging, the control circuit controls different numbers of solid-state relays to work, and the corresponding solid-state relays are turned on to connect the PTC thermistor ceramic resistors of their branches to the positive and negative busbars. At this time, the PTC thermistor ceramic resistors work and will Electrical energy is converted into heat energy. At the same time, the control circuit adjusts the wind speed of the DC fan to change the air volume passing through the surface of the PTC thermistor ceramic resistor. The solid state relay is used for rough adjustment, and the fan is used for fine adjustment. The combination of the two keeps the current of the main circuit constant.

Combining with an application structure of the control circuit in Figure 12, the control circuit is composed of a circuit breaker QF08, a fan power supply U1, a control power supply U2, a human-machine interface HMI, and a control unit MCU. Among them, the fan power supply U1 is used to generate 48V DC to provide power for the DC fan, and its input can be an external AC 220V power frequency power, or the DC power of the battery pack. The control power supply U2 is a DC/DC module, which converts the DC power provided by the battery pack into 24V DC power for the man-machine interface and the control unit to work. The control unit MCU is used to control the opening and closing of the solid state relay. In addition, it also detects the discharge current and voltage, controls the speed of the DC fan by detecting the current, and determines whether the discharge of the battery pack reaches the set value by detecting the voltage. The man-machine interface is a touch screen, through which the discharge parameters of the battery can be selected, and the discharge termination time, discharge termination voltage and discharge capacity can be set.

In this application example, a total of 32 DC adjustable-speed axial flow fans are installed in the constant current discharge device of the battery pack. Looking inside from the upper cover of the constant current discharge device of the battery pack, it can be seen that the 32 DC fans are installed equally. All DC fans are installed on the fan mounting plate on both sides inside the discharge device of the battery pack constant current discharge device.

The function of the DC fan is to keep the temperature on the surface of the PTC thermistor ceramic resistor stable at a certain point; during the discharge process, by adjusting the voltage value of the DC fan power supply, changing the speed of the DC fan, and adjusting the temperature on the surface of the PTC thermistor ceramic resistor radiator Ventilation volume, thereby changing the heating power of the PTC thermistor ceramic resistor, and stabilizing the discharge current.

The DC solid state relay is used to control the PTC thermistor ceramic resistor to connect to the main circuit. It is a non-contact switch installed between the PTC thermistor ceramic resistor and the fan. Each battery pack constant current discharge device is equipped with 26 DC solid state relays, and the DC solid state relays are divided into 10 groups, which are controlled by the drive interface of the controller. The DC solid-state relay is designed with a short-circuit protection circuit inside. When the PTC thermistor ceramic resistor has a short-circuit fault, the DC solid-state relay can be turned off instantaneously before the branch circuit breaker is protected to prevent the breakdown of the solid-state relay.

Specific embodiments of the present invention have been described above. It should be understood that the present invention is not limited to the specific embodiments described above, and those skilled in the art may make various changes or modifications within the scope of the claims, which do not affect the essence of the present invention.

Claims (10)

1. A storage battery constant current discharge device, suitable for storage battery discharge circuit, is characterized in that, comprising: resistance circuit and control circuit; The resistance circuit includes: a PTC resistance, a resistance switch and a fan assembly; The resistance switch is adapted to connect the corresponding PTC resistor to the battery discharge circuit when it is closed and short-circuit the two ends of the corresponding PTC resistor when it is disconnected, and the fan assembly is suitable for controlling the The temperature of the PTC resistor; The control circuit includes: a current detection terminal, a resistance switch control terminal and a fan speed control terminal; The current detection terminal is suitable for detecting the discharge signal in the battery discharge circuit; The resistance switch control terminal is adapted to output a first control signal of the resistance switch according to the discharge signal to control the on-off state of the resistance switch; The fan speed control terminal is adapted to output a second control signal of the fan assembly according to the discharge signal to control the speed of the fan assembly. 2. The storage battery constant current discharge device according to claim 1, wherein the storage battery includes a discharge terminal and a ground terminal, the resistance switch corresponds to a plurality of PTC resistances, and one end of the PTC resistance is respectively connected to the The discharge ends are connected, and the other ends are respectively connected to corresponding resistance switches. 3. The storage battery constant current discharge device according to claim 2, wherein one end of the PTC resistor is connected to the discharge end through a selector switch, and the control circuit further comprises: a selector switch control end, the selector switch The switch control terminal is adapted to output a third control signal to control the on-off state of the selector switch when the storage battery is discharged. 4. The battery constant current discharge device according to claim 3, wherein the selector switch is a switch tube, and the switch tube includes a first input terminal, a first output terminal and a first control terminal; An input terminal is connected to the discharge terminal, a first output terminal is connected to a corresponding PTC resistor, and a first control terminal is connected to the third control signal. 5. The battery constant current discharge device according to claim 2, wherein the resistance switch is a solid state relay, and the solid state relay includes a second input terminal, a second output terminal and a second control terminal; the first The two input terminals are respectively connected to the plurality of PTC resistors, the second output terminal is connected to the ground, and the second control terminal is connected to the first control signal. 6. The storage battery constant current discharge device according to claim 1, wherein the control circuit further comprises: a current sensor, an error amplifier and a PI regulator; The current sensor includes a current sensing input end and a current sensing output end, the current sensing input end is adapted to be connected to the discharge signal in the battery discharge circuit, and the current sensing output end is adapted to be connected to the current detection end; The error amplifier includes: a positive input terminal, a negative input terminal and an error input terminal, and the PI regulator includes: an adjustment input terminal and an adjustment output terminal; the positive input terminal is connected to a reference signal, and the negative terminal The input end is connected to the current detection end, the adjustment input end is connected to the error input end, and the adjustment output end is connected to the fan speed control end. 7 . The battery constant current discharge device according to claim 6 , wherein the control circuit further comprises: a power controller, and the adjustment output terminal is connected to the fan speed control terminal through the power controller. 8. The battery constant current discharge device according to claim 1, 6 or 7, wherein the fan assembly comprises: a DC fan. 9. The battery constant current discharge device according to claim 1, wherein the discharge signal is a discharge current, the first control signal is a control voltage, and the second control signal is a power supply voltage of a fan. 10. The battery constant current discharge device according to claim 1, characterized in that, the control circuit further comprises: a drive circuit, the drive circuit includes a drive output terminal, the drive output terminal is connected to the resistance switch control end; The driving circuit is connected to an external selection button, and is adapted to judge the discharge signal at the position of the external selection button to output the first control signal at the driving output terminal.