CN110138337B

CN110138337B - Photovoltaic cell health assessment online detection circuit and detection method for WSN node

Info

Publication number: CN110138337B
Application number: CN201910297044.8A
Authority: CN
Inventors: 黄腾飞; 谢少伟; 干嘉诚
Original assignee: Zhejiang University of Water Resources and Electric Power
Current assignee: Zhejiang University of Water Resources and Electric Power
Priority date: 2019-04-12
Filing date: 2019-04-12
Publication date: 2020-08-04
Anticipated expiration: 2039-04-12
Also published as: CN110138337A

Abstract

The invention relates to an online detection circuit and a detection method for photovoltaic cell health assessment for a WSN node. The detection circuit is characterized in that the input end of the charging control circuit is connected with the solar cell through the first MOS tube switching circuit, the output end of the charging control circuit is connected with the cell, the cell is connected with the input end of the discharging control circuit, the output end of the discharging control circuit is connected with the load through the third MOS tube switching circuit, the constant-current load circuit is connected with the second MOS tube switching circuit and then connected with the cell in parallel, and the control ends of the charging and discharging termination signals and the three MOS tube switching circuits are respectively connected with the central processing unit. The detection method comprises the steps of firstly cutting off a discharge loop to enable the battery to enter a state of only charging and not discharging; after the battery is fully charged, a charging loop is cut off, and a constant current load circuit is connected to enable the battery to enter a state of only discharging and not charging; the central processing unit respectively records the discharging time of the new battery and the old battery, and the SOH detection of the batteries is realized. The invention has accurate detection result and is convenient for replacing the battery in time.

Description

Photovoltaic cell health assessment online detection circuit and detection method for WSN node

Technical Field

The invention relates to a battery online detection system, in particular to a photovoltaic battery health assessment online detection circuit and a detection method for a WSN node.

Background

A Wireless Sensor Network (WSN) is a wireless communication network composed of a large number of sensor nodes, and when the WSN is distributed in an outdoor environment, it is difficult to obtain energy through a power line, so a photovoltaic power supply system becomes its main power supply mode in addition to battery power supply. However, as the number of charge and discharge cycles increases, the life of the battery in the photovoltaic system will gradually decrease or even become invalid, and the battery needs to be replaced in time. Therefore, it is necessary to accurately evaluate the state of health of the battery in time. However, the existing photovoltaic system for the wireless sensor node focuses on the realization of charge-discharge control and protection functions, and the photovoltaic system is often not provided with a battery health assessment function, so that the battery is not convenient to replace and remove faults in time.

At present, the state Of health Of a battery is represented by SOH (state Of health), which is defined as follows: the ratio of the dischargeable capacity of the battery to the rated capacity of the new battery under a certain condition:

SOH＝Qnow/Qnew (1.1)

where Qnow represents the maximum capacity that the battery can deliver under the current conditions, and Qnew represents the rated capacity of a new battery. When the time Tnow and Tnew from the full-charge state constant current discharge to the end voltage are recorded under the same discharge current, SOH can also be expressed by the following formula:

SOH＝Tnow/Tnew (1.2)

methods for estimating SOH can be roughly classified into two categories. One is a method for measuring SOH not based on a model, such as a discharge test method, a cycle number folding algorithm and the like; one is a model-based SOH estimation algorithm, such as an empirical model method, a resistance-fold algorithm, an impedance analysis method, and the like.

The cycle number conversion method needs to record the charge and discharge cycle number, and the charge of the solar charging system is in an indefinite state, so that the charge and discharge cycle number cannot be accurately recorded. The resistance folding algorithm only takes the resistance as the basis for evaluating the SOH, but the change range of the resistance is small when the battery is aged, so that the method has large error, and different Map maps are required to be drawn for different batteries. Impedance analysis is the leading method at present, and can more intuitively analyze the change of the SOH according to the impedance spectrum, but the method needs special equipment. The methods are not suitable for the on-line detection of the photovoltaic system SOH for the WSN node.

The SOH detection result of the discharge test method is the most accurate and is more suitable for the battery health assessment of the photovoltaic system for the WSN node.

Disclosure of Invention

The invention mainly solves the technical problems that the existing photovoltaic system for the WSN node (namely, the wireless sensing node) cannot perform online detection on the health state of the battery and cannot evaluate the health state of the battery, so that the battery cannot be replaced in time and the fault cannot be eliminated; the photovoltaic cell health assessment online detection circuit and the detection method for the WSN node can perform online detection on the cell health state of a photovoltaic system for the WSN node, assess the cell health state, facilitate timely replacement of a cell and timely troubleshooting, and accordingly ensure normal operation of the WSN node.

The technical problem of the invention is mainly solved by the following technical scheme: the invention relates to a photovoltaic cell health assessment online detection circuit for WSN nodes, which comprises a central processing unit, a charging control circuit, a discharging control circuit, a constant current load circuit, a first MOS tube switch circuit, a second MOS tube switch circuit and a third MOS tube switch circuit, wherein the input end of the charging control circuit is connected with a Solar cell Solar through the first MOS tube switch circuit, the output end of the charging control circuit is connected with a Battery Battery, the Battery Battery is also connected with the input end of the discharging control circuit, the output end of the discharging control circuit is connected with a load through the third MOS tube switch circuit, a series circuit formed by connecting the constant current load circuit and the second MOS tube switch circuit is connected with the Battery Battery in parallel, the control ends of the first MOS tube switch circuit, the second MOS tube switch circuit and the third MOS tube switch circuit, the charging termination signal output by the charging control circuit and the discharging termination signal output by the discharging control circuit are respectively connected with the central processing unit. The central processing unit can be a singlechip specially arranged for the detection circuit; when the port line of the MCU of the WSN node has redundancy and can work in a low-power-consumption power-down mode, the MCU of the WSN node can also be used together to save cost. When the single chip microcomputer is adopted, the single chip microcomputer needs to be communicated with an MCU in the WSN node. The Battery is a rechargeable Battery, namely a Battery needing evaluation detection, and supplies power to the WSN node. In the invention, the central processing unit controls the on/off of the three MOS tube switch circuits, and the charging termination signal output by the charging control circuit and the discharging termination signal output by the discharging control circuit are respectively transmitted to the central processing unit. During SOH detection, a discharge loop is cut off firstly through three MOS tube switching circuits, so that a battery enters a state of only charging and not discharging; after the battery is fully charged, the charging loop is cut off, and the constant current load circuit is switched on, so that the battery enters a state of only discharging and not charging. The method comprises the steps that the central processing unit records the discharging time from the beginning to the end of discharging of the battery, the WSN system sends the measured discharging time of the battery to the remote monitoring system, and the measured discharging time of the battery is compared with the discharging time of a new battery under the same discharging current, so that the SOH detection of the battery in the photovoltaic system for the WSN node is realized. The detection circuit is convenient to control, high in reliability and accurate in SOH detection result of the battery, is more suitable for evaluating the battery health state of the photovoltaic system for the WSN node, is convenient for replacing the battery in time and removing faults in time, and accordingly ensures the normal operation of the WSN node.

Preferably, the charging control circuit comprises a charging control chip U11, and the charging control chip U11 adopts a CN3063 charging control chip; the first MOS tube switching circuit comprises an MOS tube Q11 and an MOS tube Q12; the positive pole of the Solar cell Solar is connected with the source electrode of the MOS tube Q11, the drain electrode of the MOS tube Q11 is connected with the 4 feet of the charging control chip U11, the 4 feet of the charging control chip U11 are grounded through a capacitor C11, a resistor R11 is connected between the source electrode and the grid electrode of the MOS tube Q11, the grid electrode of the MOS tube Q11 is connected with the drain electrode of the MOS tube Q12, the source electrode of the MOS tube Q12 is connected with the negative pole of the Solar cell Solar and grounded, the grid electrode of the MOS tube Q12 is connected with a control signal K1 output by the central processing unit, the pin 1 of the charging control chip U11, the 3 pins are all grounded, the 2 pin of the charging control chip U11 is grounded through a resistor R12, the 5 pin and the 8 pin of the charging control chip U11 are connected, the 5 pin of the charging control chip U11 is grounded through a capacitor C12 and is connected with the positive electrode of a Battery, the negative electrode of the Battery is grounded, and the 6 pin of the charging control chip U11 outputs a charging termination signal C _ END to be connected with the central processing unit. The technical scheme adopts the CN3063 lithium battery solar charging control chip, and other charging control chips can be adopted as long as a charging termination signal (rising or falling edge) can be provided. MOS pipe Q11, MOS pipe Q12 and resistance R11 constitute first MOS pipe switch circuit, control the break-make of charging circuit. The MOS tube Q11 adopts a P-channel MOS tube, and the MOS tube Q12 adopts an N-channel MOS tube. The gate of the MOS transistor Q12 is the control terminal of the first MOS transistor switch circuit, and is connected to the control signal K1 output by the central processing unit. The charge termination signal C _ END is provided by pin 6 of the charge control chip U11 and is output as an open drain.

Preferably, the discharge control circuit comprises a discharge control chip U21, and the discharge control chip U21 adopts a CN302 discharge control chip; the third MOS tube switching circuit comprises a diode D22 and a MOS tube Q21; the 1 pin of the discharge control chip U21 is connected with the anode of the Battery by a resistor R21 and the 6 pin of the discharge control chip U21 by a resistor R22, the 6 pin of the discharge control chip U21 is connected with the cathode of the Battery by a resistor R23, the 2 pin of the discharge control chip U21 is grounded, the 4 pin of the discharge control chip U21 is grounded by a capacitor C21 and is connected with the source of the MOS tube Q21, the 4 pin of the discharge control chip U21 is also connected with the anode of the Battery, the drain of the MOS tube Q21 is connected with the load, the gate of the MOS tube Q21 is connected with the cathode of the diode D21 and the cathode of the diode D22, the anode of the diode D21 is connected with the 3 pin of the discharge control chip U21, the anode of the diode D22 is connected with the control signal K3 output by the central processing unit, and the gate of the MOS tube Q5 is grounded by a resistor R24 and the discharge control chip U21 and is connected with the central processing unit END 21. In the technical scheme, the CN302 discharge control chip is adopted, and other discharge control chips can be adopted as long as a discharge termination signal (rising or falling edge) can be provided. The MOS tube Q21 is a P-channel MOS tube and is used for on-off control of the load loop. The MOS tube Q21, the resistor R24, the diode D21 and the diode D22 form a third MOS tube switching circuit, the MOS tube Q21 is controlled by the discharge control chip U21 on one hand, and when the discharge reaches a termination voltage value, the MOS tube Q21 is cut off; on the other hand, the MOS transistor Q21 is controlled by the control signal K3 and is used for cutting off the load circuit when the battery health assessment online detection state is operated. Diode D21 and diode D22 are used to isolate the two control signals. The discharge END signal D _ END is provided by pin 5 of the discharge control chip U21 and is output as an open drain.

Preferably, the constant current load circuit comprises a triode Q31, a resistor R31 and a resistor R32, and the second MOS transistor switch circuit comprises a MOS transistor Q32; an emitter of the triode Q31 is connected with the positive electrode of the Battery Battery through a resistor R31, a collector of the triode Q31 is connected with the drain electrode of the MOS tube Q32 through a resistor R32, a base of the triode Q31 is connected with the positive electrode of the voltage regulator tube D31, a negative electrode of the voltage regulator tube D31 is connected with the positive electrode of the Battery Battery, the base of the triode Q31 is connected with the drain electrode of the MOS tube Q32 through a resistor R33, the source of the MOS tube Q32 is grounded, and a grid of the MOS tube Q32 is connected with a control signal K2 output by the central processing unit. The constant current load circuit can be selected according to the detection accuracy requirement of the SOH. The constant current load circuit of the technical scheme has relatively low precision (mainly linearity), and when the battery voltage is changed from 4.2V to 2.8V, and the constant current value Ib is a certain value within 1mA to 100mA, the linearity is within 3 percent. The technical scheme is a simple circuit form of the constant current load circuit, and the circuit is directly powered by a battery to be tested. The transistor Q31 is a constant current regulating transistor, and operates in the amplifying region, wherein the current I1 of the resistor R31 is kept substantially constant, and the constant current value of the circuit can be changed by changing the resistance of the resistor R31. The voltage regulator tube D31 can select a reference tube with low working current, such as a REF1004-1.2V reference tube, the minimum working current of the voltage regulator tube D31 is 10uA, the current of the voltage regulator tube D31 loop is reduced as much as possible by adjusting a resistor R33, the discharge current Tb of the battery is basically equal to the current I1, and the constant current characteristic is achieved. The resistor R32 is the load of the constant current circuit, and the resistance value of the resistor R32 is reasonably selected, so that the power consumption of the triode Q31 can be reduced. The MOS transistor Q32 forms a second MOS transistor switching circuit, and the MOS transistor Q32 is an N-channel MOS transistor, and a gate of the N-channel MOS transistor is controlled by a control signal K2 to control the constant current load circuit to be turned off or turned on.

Preferably, the constant current load circuit comprises an operational amplifier U41, and the second MOS transistor switch circuit comprises an MOS transistor Q42; the non-inverting input end of the operational amplifier U41 is connected with the positive electrode of the Battery Battery through a resistor R42 and a resistor R41, and is connected with the drain electrode of the MOS tube Q42 through a resistor R43, the connection point of the resistor R42 and the resistor R41 is connected with the negative electrode of the voltage regulator tube D41, the positive electrode of the voltage regulator tube D41 is connected with the drain electrode of the MOS tube Q42, the inverting input end of the operational amplifier U41 is connected with the emitter electrode of the triode Q41, the collector electrode of the triode Q41 is connected with the positive electrode of the Battery Battery, the output end of the operational amplifier U41 is connected with the base electrode of the triode Q41 through a resistor R44, the emitter electrode of the triode Q41 is connected with the drain electrode of the MOS tube Q42 through a resistor RN, the source electrode of the MOS tube Q42 is grounded, and the grid electrode of the MOS tube Q. The constant current load circuit in the technical scheme has relatively high precision of the constant current value, the linearity can be within 0.5%, and if the constant current value Ib is a certain value within 10mA to 100mA, the linearity is higher. The technical scheme is a circuit form based on operational amplifier of the constant current load circuit. The voltage regulator tube D41 is a reference voltage regulator tube, the resistor R41 is a current-limiting resistor, the resistor R42 and the resistor R43 are voltage dividing resistors of reference voltage, the resistor RN is a current sampling resistor, the resistor R44 is a base resistor of the triode Q41, and the operational amplifier and the reference voltage regulator tube are directly powered by a tested battery. When the voltage of the battery changes, the CE terminal voltage of the triode Q41 is changed through the feedback of the resistor RN and the adjustment of the operational amplifier and the triode Q41, the same in-phase and reverse-phase input terminal voltages of the operational amplifier are ensured, namely the voltages at two ends of the resistor RN are unchanged. When the resistance RN is a constant value, the discharge battery Ib remains unchanged, and has a constant current characteristic. The constant current value of the circuit can be changed by changing the resistance value of the resistor RN. The voltage stabilizing tube D41 can select a REF1004-1.2V reference tube or a reference tube with lower reference voltage, and is provided after voltage division, so that the voltage drop on the resistor RN is reduced, the operational amplifier and the triode Q41 have more space for adjusting voltage, the constant current value can be kept unchanged when the voltage of the battery is lower, and the working voltage range of the constant current load circuit is expanded. The MOS transistor Q42 forms a second MOS transistor switching circuit, and the MOS transistor Q42 is an N-channel MOS transistor, and a gate of the N-channel MOS transistor is controlled by a control signal K2 to control the constant current load circuit to be turned off or turned on. The operational amplifier U41 needs to use low power consumption, wide voltage range (can be directly powered by the battery to be tested), and low bias current. If HT9274 micro-power consumption operational amplifier is adopted, the working voltage range is 1.6V-5.5V, the working current is 5uA, and the bias current is 1 PA. Because the battery is used for supplying power, the working current of the circuit influences the detection accuracy of the SOH, and the values of the resistor R41, the resistor R42 and the resistor R43 are as large as possible, so that the working current of the circuit is reduced, and the detection accuracy of the SOH is improved.

The two constant current load circuits are directly powered by the battery to be tested, the constant current load circuits can work normally within the voltage range of the battery discharge test, the power consumption of the constant current load circuit device is low, and the measurement accuracy of the SOH is improved.

Preferably, the central processing unit adopts an MCU of a WSN node, the online detection circuit includes an interface JP71, the control terminals of the first MOS transistor switch circuit, the second MOS transistor switch circuit, and the third MOS transistor switch circuit, the charging termination signal output by the charging control circuit, the discharging termination signal output by the discharging control circuit, and the positive electrode and the negative electrode of the Battery are respectively connected to pins of the interface JP71, and the interface JP71 is further connected to the MCU of the WSN node. When the port line of the MCU of the WSN node has redundancy and can work in a low-power-consumption power-down mode, the MCU of the WSN node can be used as a central processing unit of the detection circuit, so that the cost is saved. The tested battery supplies power to the MCU of the WSN node through an interface JP71, control signals of the three MOS tube switching circuits can be controlled by a common I/O port of the MCU, and a charging termination signal and a discharging termination signal can be controlled by an external interrupt I/O port of the MCU. If the internal power-down awakening timer of the MCU is available, timing the discharge time of the battery by using the internal power-down awakening timer of the MCU; if the MCU does not have an internal power-down awakening timer or the internal power-down awakening timer of the MCU has insufficient precision and is unavailable, an additional real-time clock circuit is used for timing the discharge time of the battery, and the real-time clock circuit is connected with the MCU of the WSN node through an interface JP 71.

Preferably, the central processing unit comprises a singlechip U71, and the singlechip U71 adopts an STC8C1K12 singlechip; the 8 pins of the single chip microcomputer U71 are connected with the positive electrode of the Battery and are grounded through a capacitor C71, the 10 pin of the single chip microcomputer U71 is grounded, the control ends of the first MOS tube switch circuit, the second MOS tube switch circuit and the third MOS tube switch circuit and the charging termination signal output by the charging control circuit and the discharging termination signal output by the discharging control circuit are respectively connected with the 17 pins, 18 pins, 19 pins, 13 pins and 14 pins of the single chip microcomputer U71, the 11 pins and 12 pins of the single chip microcomputer U71 are respectively connected with the 3 pins and 2 pins of an interface JP72, the 3 pins and 2 pins of the interface JP72 are used as a program downloading interface of the single chip microcomputer U71 and are connected with a downloader, the 1 pin of the interface JP72 is connected with the positive electrode of the Battery, and the 4 pins of the interface JP72 are grounded; serial port communication or RS485 communication is adopted between the single chip microcomputer U1 and the WSN node; when serial port communication is adopted, the pin 3 and the pin 2 of the interface JP72 are used as communication interfaces of the single chip microcomputer U71 and the WSN node and are connected with the serial port of the WSN node; when RS485 communication is adopted, the WSN node is provided with an RS485 interfaceThe detection circuit comprises an RS485 communication interface circuit, the RS485 communication interface circuit comprises an RS485 interface chip U62, and the RS485 interface chip U62 adopts an XR33032 chip; the 3 pin and the 2 pin of the interface JP72 are respectively connected with the 1 pin and the 4 pin of the RS485 interface chip U62, the 2 pin and the 3 pin of the RS485 interface chip U62 are respectively connected with the 15 pin and the 16 pin of the singlechip U71, the 5 pin of the RS485 interface chip U62 is grounded, a resistor R63 is connected between the 5 pin and the 6 pin of the RS485 interface chip U62, a resistor R62 is connected between the 6 pin and the 7 pin of the RS485 interface chip U62, a resistor R61 is connected between the 7 pin and the 8 pin of the RS485 interface chip U62, the 8 pin of the RS485 interface chip U62 is connected with the anode of the Battery Battery and grounded through a capacitor C62, the 6 pin of the RS485 interface chip U62 outputs a signal A of RS485 through the resistor R65, the 7 pin of the RS485 interface chip U62 outputs a signal B of the RS485 through the resistor R64, a lightning protection transient S suppression signal A and TVT suppression diode 62 are respectively connected between the signal B63 and TVT suppression diode 63, the signal A and the signal B are respectively connected with a pin 1 and a pin 2 of the RS485 interface JP62, and the RS485 interface JP62 is connected with the RS485 interface of the WSN node through an RS485 signal line. The technical scheme is specially provided with a singlechip as a central processing unit of the detection circuit. The single chip microcomputer selects the single chip microcomputer with low power consumption, low voltage and wide working voltage range (can be directly supplied by a tested battery), and has a low power consumption power-down mode, a power-down awakening timer and an external interrupt port which can be triggered by a rising edge or a falling edge. Preferably selecting an STCSC1K12 singlechip, wherein the working voltage is 1.7V-5.5V; the power consumption of the power-down mode can be reduced to be below 0.1uA, and a 32K power-down awakening timer is arranged; an external interrupt port which can be triggered by INTO and INT1 rising edges and falling edges; having a structure of²The interface C can directly drive the real-time clock chip; the system is provided with an internal high-precision clock, an internal reset and watchdog circuit, and peripheral circuits of the single chip microcomputer can be simplified; has strong anti-electromagnetic interference capability. In the technical scheme, the singlechip is directly supplied with power by the battery to be detected, and an internal clock and a reset circuit of the singlechip are adopted. The interface JP72 is a program downloading interface of the single chip microcomputer, and is also a communication interface between the single chip microcomputer and the MCU of the WSN node. If the internal power-down awakening timer of the singlechip is available, the timer is usedThe method comprises the steps of utilizing an internal power-down awakening timer of a single chip microcomputer to time the discharge time of a battery, utilizing an external real-time clock circuit to time the discharge time of the battery if the single chip microcomputer does not have the internal power-down awakening timer or the internal power-down awakening timer is not enough and cannot be used, and utilizing an SDA signal and an SC L signal of the real-time clock circuit to be respectively connected with a pin 7 and a pin 9 of the single chip microcomputer.

Preferably, the photovoltaic cell health assessment online detection circuit for the WSN node comprises a real-time clock circuit, and the real-time clock circuit is connected with the central processing unit. If the internal power-down awakening timer of the central processing unit is available, timing the discharge time of the battery by using the internal power-down awakening timer of the central processing unit; if the central processing unit does not have the internal power-down awakening timer or the internal power-down awakening timer is not accurate enough and is not available, the discharge time of the battery needs to be timed by adding a real-time clock circuit.

The detection method of the photovoltaic cell health assessment online detection circuit for the WSN node comprises the following steps: when the central processing unit receives an SOH detection command issued by a high layer (such as a remote monitoring system), the central processing unit outputs a control signal K3, the third MOS tube switching circuit is turned off, a load loop is cut off, the Battery is in a state of being only charged and not discharged, and the central processing unit is in a low-power-consumption power-down state (the working current can be generally less than 1 uA); once the Battery is fully charged, the charging control circuit sends a charging termination signal C _ END to the central processing unit to wake up the central processing unit in a low-power-consumption power-down state, the central processing unit outputs a control signal K1 to turn off the first MOS tube switching circuit and cut off a charging loop, and simultaneously the central processing unit outputs a control signal K2 to turn on the second MOS tube switching circuit and access the constant-current load circuit to perform a discharging test, and the central processing unit utilizes an internal power-down wake-up timer or an external real-time clock circuit to perform timing and enters the low-power-consumption power-down state; when the battery discharges to the END voltage, the discharge control circuit sends a discharge END signal D _ END to the central processing unit to awaken the central processing unit in the low-power-consumption power-down state, and the central processing unit records the discharge time Tnow of the battery; when a new battery is just used, the discharge time Tnew can be tested once according to the process under the same condition; according to the formula 1.2, the SOH parameter of the battery can be obtained; after the discharge detection test is finished, the central processing unit respectively sends out a control signal K1, a control signal K2 and a control signal K3, the second MOS tube switch circuit is turned off, the first MOS tube switch circuit and the third MOS tube switch circuit are turned on, and the Battery enters a normal charge-discharge state. Because the discharge time Tnew of the new battery is the same as the test condition of the discharge time Tnow of the current battery, the error caused by the precision of the constant current load circuit can be offset, so that the SOH measurement precision is improved. When a simple constant current load circuit is adopted, the improvement of the SOH measurement precision is particularly obvious.

Preferably, the timing method of the discharge time of the battery includes the following two methods:

firstly, the discharge time of the battery is timed by the internal power-off wake-up timer of the central processing unit, and the following detections are respectively carried out on a new battery and a current battery: starting Battery discharge, waking up a primary central processing unit after timing time of power-down wake-up overflows each time, counting the timing overflow time by +1, entering a power-down state, and circulating the steps; when the discharging termination signal output by the discharging control circuit wakes up the central processing unit in the power-down state for the last time, reading the timing value of the internal power-down wake-up timer at the moment, and adding the counted timing overflow total time to obtain the discharging time of the battery; detecting the new battery to obtain the discharge time Tnew of the new battery; detecting the current battery to obtain the discharge time Tnow of the current battery; the state of health SOH of the current battery is Tnow/Tnew;

secondly, when the central processing unit has no internal power-down wake-up timer, or the internal power-down wake-up timer of the central processing unit has low precision, the discharging time of the battery is timed by a real-time clock circuit additionally arranged on the central processing unit, and the following detections are respectively carried out on a new battery and a current battery: timing by using the real-time clock circuit, reading the time of the primary real-time clock circuit when Battery Battery discharge starts, and reading the time of the primary real-time clock circuit again when discharge ends, wherein the secondary time difference is the discharge time of the Battery; detecting the new battery to obtain the discharge time Tnew of the new battery; detecting the current battery to obtain the discharge time Tnow of the current battery; the state of health SOH of the current battery is Tnow/Tnew.

The discharge time Tnew of the new battery and the discharge time Tnow of the current battery obtained by the central processing unit are respectively transmitted to a remote monitoring system by the WSN node, and the state of health (SOH) of the current battery is obtained by the remote monitoring system through calculation.

The invention has the beneficial effects that: through three MOS tube switch circuits, when SOH is detected, a discharging loop is cut off firstly, so that a battery enters a state of only charging and not discharging; after the battery is fully charged, the charging loop is cut off, and the constant current load circuit is switched on, so that the battery enters a state of only discharging and not charging. The method comprises the steps that the central processing unit records the discharging time from the beginning to the end of discharging of the battery, the WSN system sends the measured discharging time of the battery to the remote monitoring system, and the measured discharging time of the battery is compared with the discharging time of a new battery under the same discharging current, so that the SOH detection of the battery in the photovoltaic system for the WSN node is realized. The detection circuit is convenient to control, high in reliability and accurate in SOH detection result of the battery, is more suitable for evaluating the battery health state of the photovoltaic system for the WSN node, is convenient for replacing the battery in time and removing faults in time, and accordingly ensures the normal operation of the WSN node.

Drawings

Fig. 1 is a block diagram of a circuit schematic connection structure of the present invention.

Fig. 2 is a schematic circuit diagram of the charge control circuit and the first MOS transistor switch circuit according to the present invention.

Fig. 3 is a schematic circuit diagram of a discharge control circuit and a third MOS transistor switch circuit according to the present invention.

Fig. 4 is a schematic circuit diagram of a constant current load circuit and a second MOS transistor switch circuit according to the present invention.

Fig. 5 is another circuit schematic diagram of the constant current load circuit and the second MOS transistor switching circuit of the present invention.

Fig. 6 is a schematic circuit diagram of the interface JP71 according to the invention.

Fig. 7 is a circuit schematic diagram of the single chip microcomputer U71 in the invention.

Fig. 8 is a circuit schematic diagram of an RS485 communication interface circuit in the present invention.

Fig. 9 is a circuit schematic of the real time clock circuit of the present invention.

In the figure, 1, a central processing unit, 2, a charging control circuit, 3, a discharging control circuit, 4, a constant current load circuit, 5, a first MOS tube switch circuit, 6, a second MOS tube switch circuit, 7, a third MOS tube switch circuit and 8, a load.

Detailed Description

The technical scheme of the invention is further specifically described by the following embodiments and the accompanying drawings.

Example 1: the photovoltaic cell health assessment online detection circuit for the WSN node in the embodiment includes, as shown in fig. 1, a central processing unit 1, a charge control circuit 2, a discharge control circuit 3, a constant current load circuit 4, a first MOS transistor switch circuit 5, a second MOS transistor switch circuit 6, and a third MOS transistor switch circuit 7, where an input end of the charge control circuit is connected to a Solar cell Solar through the first MOS transistor switch circuit, an output end of the charge control circuit is connected to a Battery, the Battery is connected to an input end of the discharge control circuit, an output end of the discharge control circuit is connected to a load 8 through the third MOS transistor switch circuit, a series circuit formed by connecting the constant current load circuit and the second MOS transistor switch circuit is connected in parallel to the Battery, a charge termination signal output by the first MOS transistor switch circuit, the second MOS transistor switch circuit, a control end of the third MOS transistor switch circuit, and the charge control circuit, The discharge control circuit outputs discharge termination signals respectively connected with the central processing unit.

In this embodiment, the central processing unit adopts an MCU of a WSN node, and the online detection circuit is connected to the MCU of the WSN node through an interface JP 71. As shown in fig. 6, pins 1 and 9 of the interface JP71 are respectively connected to the positive electrode and the negative electrode of the Battery and supply power to the WSN node by means of a connection cable or a printed circuit board, pins 2, 3 and 4 of the interface JP71 are respectively connected to a control signal K1, a control signal K2 and a control signal K3 output by the MCU of the WSN node by means of a connection cable or a printed circuit board, and pins 5 and 6 of the interface JP71 respectively transmit a charging termination signal C _ END and a discharging termination signal D _ END to the MCU of the WSN node by means of a connection cable or a printed circuit board.

As shown in fig. 2, the charging control circuit includes a charging control chip U11, the charging control chip U11 adopts CN3063 charging control chip; the first MOS tube switching circuit comprises a MOS tube Q11 and a MOS tube Q12; the positive pole of the Solar cell Solar is connected with the source electrode of an MOS tube Q11, the drain electrode of the MOS tube Q11 is connected with the 4 pin of a charging control chip U11, the 4 pin of the charging control chip U11 is grounded through a capacitor C11, a resistor R11 is connected between the source electrode and the grid electrode of the MOS tube Q11, the grid electrode of the MOS tube Q11 is connected with the drain electrode of the MOS tube Q12, the source electrode of the MOS tube Q12 is connected with the negative pole of the Solar cell Solar and is grounded, the grid electrode of the MOS tube Q12 is connected with the 2 pin of an interface JP71, the 1 pin and the 3 pin of the charging control chip U11 are grounded, the 2 pin of the charging control chip U11 is grounded through a resistor R12, the 5 pin and the 8 pin of the charging control chip U11 are connected, the 5 pin of the charging control chip U11 is grounded through a capacitor C12 and is connected with the positive pole of the Battery Battery, the negative pole of the Battery Battery is grounded, and the output signal JP 11 is connected with the interface JP 5 _ C.

As shown in fig. 3, the discharge control circuit includes a discharge control chip U21, the discharge control chip U21 adopts a CN302 discharge control chip; the third MOS tube switching circuit comprises a diode D22 and a MOS tube Q21; a pin 1 of the discharge control chip U21 is connected with the positive electrode of the Battery via a resistor R21 and a pin 6 of the discharge control chip U21 via a resistor R22, a pin 6 of the discharge control chip U21 is connected with the negative electrode of the Battery via a resistor R23, a pin 2 of the discharge control chip U21 is grounded, a pin 4 of the discharge control chip U21 is grounded via a capacitor C21 and is connected with the source of the MOS transistor Q21, a pin 4 of the discharge control chip U21 is also connected with the positive electrode of the Battery, the drain of the MOS transistor Q21 is connected with the load, the gate of the MOS transistor Q21 is connected with the negative electrode of the diode D21 and the diode D22, the positive electrode of the diode D21 is connected with the pin 3 of the discharge control chip U21, the positive electrode of the diode D22 is connected with the pin 4 of the interface JJP71, the gate of the MOS transistor Q21 is grounded via a resistor R24, and the discharge control chip U21 has its discharge control pin 3 terminating signal output and the pin en 9.

As shown in fig. 4, the constant current load circuit includes a transistor Q31, a resistor R31 and a resistor R32, and the second MOS transistor switch circuit includes a MOS transistor Q32; an emitter of the triode Q31 is connected with the positive electrode of the Battery Battery through a resistor R31, a collector of the triode Q31 is connected with the drain electrode of the MOS tube Q32 through a resistor R32, a base of the triode Q31 is connected with the positive electrode of the voltage regulator tube D31, a negative electrode of the voltage regulator tube D31 is connected with the positive electrode of the Battery Battery, the base of the triode Q31 is connected with the drain electrode of the MOS tube Q32 through a resistor R33, the source of the MOS tube Q32 is grounded, and the gate of the MOS tube Q32 is connected with the 3 pin of the interface JJP 71.

The detection method of the photovoltaic cell health assessment online detection circuit for the WSN node comprises the following steps: when the MCU of the WSN node receives an SOH detection command sent by a high layer (such as a remote monitoring system), the MCU of the WSN node outputs a control signal K3, an MOS tube Q21 is turned off, a load loop is cut off, a Battery enters a state of being only charged and not discharged, and the MCU of the WSN node enters a low-power-consumption power-down state (the working current can be generally less than 1 uA). Once the battery is fully charged, the charging control circuit sends a charging termination signal C _ END to wake up the MCU of the WSN node in the low-power-consumption power-down state, the MCU of the WSN node outputs a control signal K1 again, the MOS tube Q11 is turned off, the charging loop is cut off, meanwhile, the MCU of the WSN node outputs a control signal K2 again, the MOS tube Q32 is turned on, the constant-current load circuit is connected, a discharging test is carried out, and the MCU of the WSN node can enter the low-power-consumption power-down state again after a timer is started. When the battery discharges to the END voltage, the discharge control circuit sends a discharge END signal D _ END, the MCU of the WSN node in the low-power-consumption power-down state is awakened again, and the MCU of the WSN node records the discharge time Tnow. According to the formula 1.2, the SOH parameter of the battery can be obtained by comparing the time with the discharge time Tnew under the same condition of a new battery. After the discharging test is finished, the MCU of the WSN node outputs a control signal K1, a control signal K2 and a control signal K3, the MOS tube Q32 is turned off, the MOS tube Q11 and the MOS tube Q21 are turned on, and the Battery to be detected can enter a normal charging and discharging state;

the timing method for the discharge time of the battery comprises the following steps: the discharge time of the battery is timed by an internal power-down awakening timer of the MCU of the WSN node, and the following detections are respectively carried out on the new battery and the current battery: starting Battery discharge, waking up the MCU once after the timed time of power-down wake-up overflows each time, counting the timed overflow time by +1, entering a power-down state, and repeating the steps; when the discharging termination signal output by the discharging control circuit wakes up the MCU in the power-down state for the last time, reading the timing value of the internal power-down wake-up timer at the moment, and adding the counted total time of timing overflow to the timing wake-up timer to obtain the discharging time of the battery; when a new battery is just used, the new battery is detected once according to the method, and the MCU obtains the discharge time Tnew of the new battery and sends the discharge time Tnew to the remote monitoring system for recording; after the battery is used for a period of time, the current battery is detected according to the method, and the MCU acquires the discharge time Tnow of the current battery and sends the discharge time Tnow to the remote monitoring system for recording; and obtaining the state of health SOH of the current battery by the remote monitoring system through calculation, wherein the state of health SOH is Tnow/Tnew.

Example 2: in the photovoltaic cell health assessment online detection circuit for the WSN node of the present embodiment, as shown in fig. 5, the constant current load circuit includes an operational amplifier U41, and the second MOS transistor switching circuit includes a MOS transistor Q42; the non-inverting input end of the operational amplifier U41 is connected with the positive electrode of the Battery Battery through a resistor R42 and a resistor R41, and is connected with the drain electrode of the MOS tube Q42 through a resistor R43, the connection point of the resistor R42 and the resistor R41 is connected with the negative electrode of the voltage regulator tube D41, the positive electrode of the voltage regulator tube D41 is connected with the drain electrode of the MOS tube Q42, the inverting input end of the operational amplifier U41 is connected with the emitter electrode of the triode Q41, the collector electrode of the triode Q41 is connected with the positive electrode of the Battery Battery, the output end of the operational amplifier U41 is connected with the base electrode of the triode Q41 through a resistor R44, the emitter electrode of the triode Q41 is connected with the drain electrode of the MOS tube Q42 through a resistor RN, the source electrode of the MOS tube Q42 is grounded, and the grid electrode. The rest of the structure is the same as that of example 1. In this embodiment, the control signal K2 output by the MCU of the WSN node controls the turn-off or turn-on of the MOS transistor Q42, and the rest of the working process is the same as that of embodiment 1. The detection method was the same as in example 1.

Example 3: the photovoltaic cell health assessment online detection circuit for the WSN node is different from the photovoltaic cell health assessment online detection circuit in the embodiment 1 in that the central processing unit is a single chip microcomputer specially arranged in the detection circuit, the WSN node in the embodiment is provided with an RS485 interface, and the single chip microcomputer U1 and the WSN node are communicated through RS485, so that an RS485 communication interface circuit needs to be added. As shown in fig. 7 and 8, the central processing unit includes a single chip microcomputer U71, and the single chip microcomputer U71 adopts an STC8C1K12 single chip microcomputer; the RS485 communication interface circuit comprises an RS485 interface chip U62, and the RS485 interface chip U62 adopts an XR33032 chip. An 8 pin of a singlechip U71 is connected with the anode of a Battery and is grounded through a capacitor C71, a 10 pin of the singlechip U71 is grounded, a grid electrode of an MOS tube Q12, a grid electrode of an MOS tube Q32 and the anode of a diode D22 are respectively connected with a 17 pin, an 18 pin and a 19 pin of the singlechip U71, a charging termination signal C _ END output by a 6 pin of a charging control chip U11 and a discharging termination signal D _ END output by a 5 pin of a discharging control chip U21 are respectively connected with a 13 pin and a 14 pin of the singlechip U71, a 11 pin and a 12 pin of the singlechip U71 are respectively connected with a 3 pin and a 2 pin of an interface JP72, the 3 pin and the 2 pin of the interface JP72 are used as a program downloading interface of a singlechip U71 and are connected with a downloader, a 1 pin of the interface JP72 is connected with the Battery and a 4 pin of the interface JP72 is grounded; the 3 pin and the 2 pin of the interface JP72 are respectively connected with the 1 pin and the 4 pin of the RS485 interface chip U62, the 2 pin and the 3 pin of the RS485 interface chip U62 are respectively connected with the 15 pin and the 16 pin of the singlechip U71, the 5 pin of the RS485 interface chip U62 is grounded, a resistor R63 is connected between the 5 pin and the 6 pin of the RS485 interface chip U62, a resistor R62 is connected between the 6 pin and the 7 pin of the RS485 interface chip U62, a resistor R61 is connected between the 7 pin and the 8 pin of the RS485 interface chip U62, the 8 pin of the RS485 interface chip U62 is connected with the anode of the Battery Battery and grounded through a capacitor C62, the 6 pin of the RS485 interface chip U62 outputs a signal A of RS485 through the resistor R65, the 7 pin of the RS485 interface chip U62 outputs a signal B of the RS485 through the resistor R64, a lightning protection transient S suppression signal A and TVT suppression diode 62 are respectively connected between the signal B63 and TVT suppression diode 63, the signal A and the signal B are respectively connected with a pin 1 and a pin 2 of the RS485 interface JP62, and the RS485 interface JP62 is connected with the RS485 interface of the WSN node through an RS485 signal line. The rest of the structure is the same as that of example 1.

The detection method of the photovoltaic cell health assessment online detection circuit for the WSN node comprises the following steps: an SOH detection command sent by a high layer (such as a remote monitoring system) is sent to a single chip microcomputer U71 through an RS485 signal by an MCU of a WSN node, and the single chip microcomputer U71 outputs a control signal K1, a control signal K2 and a control signal K3 so as to control the turn-off or turn-on of an MOS tube Q11, an MOS tube Q32 and an MOS tube Q21; a charging termination signal C _ END sent by the charging control circuit and a discharging termination signal D _ END sent by the discharging control circuit are respectively transmitted to the single chip microcomputer U71, the discharging time is recorded by the single chip microcomputer U71, then the discharging time is sent to the WSN node through the RS485 communication interface circuit, and then the discharging time is sent to the remote monitoring system by the WSN node for recording;

the timing method for the discharge time of the battery comprises the following steps: the timer is awakened by the internal power-down of the single chip microcomputer U71 for timing, and the following detections are respectively carried out on the new battery and the current battery: starting Battery discharge, waking up a single-chip microcomputer after the timed time of power-down wake-up overflows each time, counting the timed overflow time by +1, entering a power-down state, and repeating the steps; when the discharging termination signal output by the discharging control circuit wakes up the singlechip U71 in the power-down state for the last time, the timing value of the internal power-down wake-up timer at the time is read, and the total time of the timing overflow counted in the previous time is added, so that the discharging time of the battery is obtained; when the new battery is just used, the new battery is detected once according to the method, the single chip microcomputer U71 obtains the discharge time Tnew of the new battery, the discharge time Tnew is sent to the WSN node through the RS485 communication interface circuit, and then the discharge time Tnew is sent to the remote monitoring system by the WSN node for recording; after the battery is used for a period of time, the current battery is detected according to the method, the single chip microcomputer U71 obtains the discharge time Tnow of the current battery, the discharge time Tnow is sent to the WSN node through the RS485 communication interface circuit, and then the discharge time Tnow is sent to the remote monitoring system by the WSN node to be recorded; and obtaining the state of health SOH of the current battery by the remote monitoring system through calculation, wherein the state of health SOH is Tnow/Tnew.

Example 4: in the photovoltaic cell health assessment online detection circuit for the WSN node, it is considered that if the central processing unit does not have the internal power-down wake-up timer, or the accuracy of the internal power-down wake-up timer of the central processing unit is low, and the timing accuracy needs to be improved, the detection circuit needs to be additionally provided with a real-time clock circuit connected with the central processing unit, so as to time the battery discharge time. In this embodiment, a single chip microcomputer U71 and an RS485 communication interface circuit are adopted, as shown in fig. 9, the real-time clock circuit includes a real-time clock chip U51, and the real-time clock chip U51 adopts a PCF8563 chip; a pin 1 of the real-time clock chip U51 is grounded through a capacitor C51 and is connected with a pin 2 of the real-time clock chip U51 through a crystal oscillator Y51, a pin 4 of the real-time clock chip U51 is grounded, a pin 8 of the real-time clock chip U51 is connected with the positive electrode of a Battery and is grounded through a capacitor C52, and a pin 5 and a pin 6 of the real-time clock chip U51 are connected with a pin 7 and a pin 9 of the singlechip U71 respectively. The rest of the structure is the same as that of example 3.

The detection method of the photovoltaic cell health assessment online detection circuit for the WSN node in the embodiment utilizes the real-time clock chip to time the discharge time of the cell, and the timing method of the discharge time of the cell comprises the following steps: timing by using a real-time clock chip, reading the time of the primary real-time clock chip by the singlechip when Battery Battery discharge starts, and reading the time of the primary real-time clock chip again when the discharge ends, wherein the secondary time difference is the discharge time of the Battery; when the new battery is just used, the new battery is detected once according to the method, the single chip microcomputer U71 obtains the discharge time Tnew of the new battery, the discharge time Tnew is sent to the WSN node through the RS485 communication interface circuit, and then the discharge time Tnew is sent to the remote monitoring system by the WSN node for recording; after the battery is used for a period of time, the current battery is detected according to the method, the single chip microcomputer U71 obtains the discharge time Tnow of the current battery, the discharge time Tnow is sent to the WSN node through the RS485 communication interface circuit, and then the discharge time Tnow is sent to the remote monitoring system by the WSN node to be recorded; and obtaining the state of health SOH of the current battery by the remote monitoring system through calculation, wherein the state of health SOH is Tnow/Tnew. The rest of the detection methods were the same as in example 3.

Example 5: the photovoltaic cell health assessment online detection circuit for the WSN node in the embodiment is different from the embodiment 1 in that a real-time clock circuit is additionally arranged, the real-time clock circuit is shown in fig. 9, a pin 5 and a pin 6 of a real-time clock chip U51 are respectively connected with a pin 7 and a pin 8 of an interface JP71, and the pin 7 and the pin 8 of the interface JP71 are connected to an MCU of the WSN node through a connecting cable. The rest of the structure is the same as that of example 1. In the embodiment, if the MCU of the WSN node does not have the internal power-down wake-up timer, or the accuracy of the internal power-down wake-up timer of the MCU of the WSN node is low, the real-time clock circuit is used to time the battery discharge time when the timing accuracy needs to be improved. The working process and control method of this embodiment are the same as those of embodiment 1. The difference between the timing method for the discharge time of the battery in this embodiment and embodiment 4 is that the discharge time detected by the real-time clock circuit is read by the MCU of the WSN node through the interface JP71 and then sent to the remote monitoring system for recording.

Claims

1. An on-line detection circuit for the health evaluation of a photovoltaic cell for a WSN node is characterized by comprising a central processing unit, a charging control circuit, a discharging control circuit, a constant current load circuit, a first MOS tube switch circuit, a second MOS tube switch circuit and a third MOS tube switch circuit, wherein the input end of the charging control circuit is connected with a Solar cell Solar through the first MOS tube switch circuit, the output end of the charging control circuit is connected with a Battery cell, the Battery cell is also connected with the input end of the discharging control circuit, the output end of the discharging control circuit is connected with a load through the third MOS tube switch circuit, a series circuit formed by connecting the constant current load circuit and the second MOS tube switch circuit is connected with the Battery cell in parallel, the control ends of the first MOS tube switch circuit, the second MOS tube switch circuit and the third MOS tube switch circuit, and the charging termination signal output by the charging control circuit and the discharging termination signal output by the discharging control circuit are respectively connected with the central processing unit;

the constant current load circuit comprises a triode Q31, a resistor R31 and a resistor R32, and the second MOS tube switch circuit comprises an MOS tube Q32; an emitter of a triode Q31 is connected with the positive electrode of a Battery Battery through a resistor R31, a collector of a triode Q31 is connected with the drain electrode of a MOS tube Q32 through a resistor R32, the base of a triode Q31 is connected with the positive electrode of a voltage regulator tube D31, the negative electrode of the voltage regulator tube D31 is connected with the positive electrode of the Battery Battery, the base of the triode Q31 is connected with the drain electrode of the MOS tube Q32 through a resistor R33, the source of the MOS tube Q32 is grounded, and the grid of the MOS tube Q32 is connected with a control signal K2 output by the central processing unit;

or the constant current load circuit comprises an operational amplifier U41, and the second MOS tube switching circuit comprises an MOS tube Q42; the non-inverting input end of the operational amplifier U41 is connected with the positive electrode of the Battery Battery through a resistor R42 and a resistor R41, and is connected with the drain electrode of the MOS tube Q42 through a resistor R43, the connection point of the resistor R42 and the resistor R41 is connected with the negative electrode of the voltage regulator tube D41, the positive electrode of the voltage regulator tube D41 is connected with the drain electrode of the MOS tube Q42, the inverting input end of the operational amplifier U41 is connected with the emitter electrode of the triode Q41, the collector electrode of the triode Q41 is connected with the positive electrode of the Battery Battery, the output end of the operational amplifier U41 is connected with the base electrode of the triode Q41 through a resistor R44, the emitter electrode of the triode Q41 is connected with the drain electrode of the MOS tube Q42 through a resistor RN, the source electrode of the MOS tube Q42 is grounded, and the grid electrode of the MOS tube Q.

2. The photovoltaic cell health assessment online detection circuit for the WSN node as claimed in claim 1, wherein the charging control circuit comprises a charging control chip U11, the charging control chip U11 adopts a CN3063 charging control chip; the first MOS tube switching circuit comprises an MOS tube Q11 and an MOS tube Q12; the positive pole of the Solar cell Solar is connected with the source electrode of the MOS tube Q11, the drain electrode of the MOS tube Q11 is connected with the 4 feet of the charging control chip U11, the 4 feet of the charging control chip U11 are grounded through a capacitor C11, a resistor R11 is connected between the source electrode and the grid electrode of the MOS tube Q11, the grid electrode of the MOS tube Q11 is connected with the drain electrode of the MOS tube Q12, the source electrode of the MOS tube Q12 is connected with the negative pole of the Solar cell Solar and grounded, the grid electrode of the MOS tube Q12 is connected with a control signal K1 output by the central processing unit, the pin 1 of the charging control chip U11, the 3 pins are all grounded, the 2 pin of the charging control chip U11 is grounded through a resistor R12, the 5 pin and the 8 pin of the charging control chip U11 are connected, the 5 pin of the charging control chip U11 is grounded through a capacitor C12 and is connected with the positive electrode of a Battery, the negative electrode of the Battery is grounded, and the 6 pin of the charging control chip U11 outputs a charging termination signal C _ END to be connected with the central processing unit.

3. The photovoltaic cell health assessment online detection circuit for the WSN node as claimed in claim 1, wherein the discharge control circuit comprises a discharge control chip U21, the discharge control chip U21 adopts a CN302 discharge control chip; the third MOS tube switching circuit comprises a diode D22 and a MOS tube Q21; the 1 pin of the discharge control chip U21 is connected with the anode of the Battery by a resistor R21 and the 6 pin of the discharge control chip U21 by a resistor R22, the 6 pin of the discharge control chip U21 is connected with the cathode of the Battery by a resistor R23, the 2 pin of the discharge control chip U21 is grounded, the 4 pin of the discharge control chip U21 is grounded by a capacitor C21 and is connected with the source of the MOS tube Q21, the 4 pin of the discharge control chip U21 is also connected with the anode of the Battery, the drain of the MOS tube Q21 is connected with the load, the gate of the MOS tube Q21 is connected with the cathode of the diode D21 and the cathode of the diode D22, the anode of the diode D21 is connected with the 3 pin of the discharge control chip U21, the anode of the diode D22 is connected with the control signal K3 output by the central processing unit, and the gate of the MOS tube Q5 is grounded by a resistor R24 and the discharge control chip U21 and is connected with the central processing unit END 21.

4. An on-line detection circuit for photovoltaic cell health assessment of WSN node as claimed in claim 1, 2 or 3, wherein said central processing unit employs MCU of WSN node, said on-line detection circuit includes interface JP71, the control terminals of said first MOS transistor switch circuit, second MOS transistor switch circuit, third MOS transistor switch circuit, the charge termination signal output by the charge control circuit, the discharge termination signal output by the discharge control circuit and the positive and negative electrodes of Battery Battery are respectively connected to the respective pins of interface JP71, and interface JP71 is further connected to MCU of WSN node.

5. The photovoltaic cell health assessment online detection circuit for the WSN node as claimed in claim 1, 2 or 3, wherein the central processing unit comprises a single chip microcomputer U71, the single chip microcomputer U71 adopts STC8C1K12 single chip microcomputer; the 8 pins of the single chip microcomputer U71 are connected with the positive electrode of the Battery and are grounded through a capacitor C71, the 10 pin of the single chip microcomputer U71 is grounded, the control ends of the first MOS tube switch circuit, the second MOS tube switch circuit and the third MOS tube switch circuit and the charging termination signal output by the charging control circuit and the discharging termination signal output by the discharging control circuit are respectively connected with the 17 pins, 18 pins, 19 pins, 13 pins and 14 pins of the single chip microcomputer U71, the 11 pins and 12 pins of the single chip microcomputer U71 are respectively connected with the 3 pins and 2 pins of an interface JP72, the 3 pins and 2 pins of the interface JP72 are used as a program downloading interface of the single chip microcomputer U71 and are connected with a downloader, the 1 pin of the interface JP72 is connected with the positive electrode of the Battery, and the 4 pins of the interface JP72 are grounded; serial port communication or RS485 communication is adopted between the single chip microcomputer U1 and the WSN node; when serial port communication is adopted, the pin 3 and the pin 2 of the interface JP72 are used as communication interfaces of the single chip microcomputer U71 and the WSN node and are connected with the serial port of the WSN node; when RS485 communication is adopted, the WSN node is provided with an RS485 interface, the detection circuit comprises an RS485 communication interface circuit, the RS485 communication interface circuit comprises an RS485 interface chip U62, and an XR33032 chip is adopted as the RS485 interface chip U62; the 3 pin and the 2 pin of the interface JP72 are respectively connected with the 1 pin and the 4 pin of the RS485 interface chip U62, the 2 pin and the 3 pin of the RS485 interface chip U62 are respectively connected with the 15 pin and the 16 pin of the singlechip U71, the 5 pin of the RS485 interface chip U62 is grounded, a resistor R63 is connected between the 5 pin and the 6 pin of the RS485 interface chip U62, a resistor R62 is connected between the 6 pin and the 7 pin of the RS485 interface chip U62, a resistor R61 is connected between the 7 pin and the 8 pin of the RS485 interface chip U62, the 8 pin of the RS485 interface chip U62 is connected with the anode of the Battery Battery and grounded through a capacitor C62, the 6 pin of the RS485 interface chip U62 outputs a signal A of RS485 through the resistor R65, the 7 pin of the RS485 interface chip U62 outputs a signal B of the RS485 through the resistor R64, a lightning protection transient S suppression signal A and TVT suppression diode 62 are respectively connected between the signal B63 and TVT suppression diode 63, the signal A and the signal B are respectively connected with a pin 1 and a pin 2 of the RS485 interface JP62, and the RS485 interface JP62 is connected with the RS485 interface of the WSN node through an RS485 signal line.

6. The photovoltaic cell health assessment online detection circuit for the WSN node as claimed in claim 1, 2 or 3, characterized by comprising a real-time clock circuit, wherein the real-time clock circuit is connected with the central processing unit.

7. The detection method of the photovoltaic cell health assessment online detection circuit for the WSN node as claimed in claim 1, wherein when the central processing unit receives an SOH detection command issued by a high layer, the central processing unit outputs a control signal to turn off the third MOS transistor switch circuit and cut off a load loop, the Battery Battery enters a state of charging and discharging only, and the central processing unit enters a low power consumption power-down state; once the Battery is fully charged, the charging control circuit sends a charging termination signal to the central processing unit to wake up the central processing unit in a low-power-consumption power-down state, the central processing unit outputs a control signal to turn off the first MOS tube switching circuit and cut off a charging loop, and simultaneously outputs a control signal to turn on the second MOS tube switching circuit, and then the second MOS tube switching circuit is connected to the constant-current load circuit to perform a discharging test, and the central processing unit utilizes an internal power-down wake-up timer or an external real-time clock circuit to time and then enters the low-power-consumption power-down state; when the battery discharges to the end voltage, the discharge control circuit sends a discharge end signal to the central processing unit to wake up the central processing unit in a low-power-consumption power-down state, the central processing unit records the discharge time Tnow of the battery, and the time is compared with the discharge time Tnew measured under the same condition of a new battery, so that the SOH parameter of the battery is obtained; after the discharge detection test is finished, the central processing unit respectively sends out control signals to turn off the second MOS tube switch circuit and turn on the first MOS tube switch circuit and the third MOS tube switch circuit, and the Battery enters a normal charge-discharge state;

the timing method of the discharge time of the battery includes the following two methods: