CN106646267B - Method and device for detecting service life of battery of power distribution terminal - Google Patents

Abstract

The invention discloses a distribution terminal battery life detection method and device. The method includes: obtaining the terminal voltage at both ends of the detected battery, detecting the internal resistance of the detected battery; when the internal resistance detection is completed, performing a test on the detected battery. Discharge test to obtain a short-time discharge curve; according to the detection initial voltage and detection end voltage, the detection reference voltage point is obtained; and the standard discharge curve of the tested battery is obtained to obtain the standard slope; and then according to the capacity calculation formula, the capacity of the tested battery is obtained Estimated value; perform internal resistance and temperature compensation on the tested battery to obtain the actual capacity of the tested battery. The method and device provided by the present invention test the actual capacity of the battery to be detected based on the short-time discharge of the voltage change rate. The test time is short, there is no need to discharge all the power of the battery to be detected, reducing the waste of energy, and comprehensively considering the capacity, The relationship between temperature and internal resistance, the capacity test is accurate, and the health status of the tested battery is reasonably evaluated.

Description

Distribution terminal battery life detection method and device

Technical field

The invention relates to the technical field of power distribution automation, and in particular to a method and device for detecting battery life of a power distribution terminal.

Background technique

The battery of the distribution terminal equipment serves as a backup power supply to continuously supply power to the terminal. When there is a power outage on site, the battery pack will become the only power source for the distribution terminal to work. In recent years, as users have higher and higher requirements for power supply reliability, distribution terminals are also widely used in distribution automation. Once the battery has problems such as aging or insufficient capacity, it may cause the distribution terminal to not work properly. , causing the power distribution automation system to fail. Therefore, it is necessary to regularly test the performance of the battery and understand the health status of the battery in a timely manner.

At present, the existing detection methods for distribution terminal battery capacity are check discharge method and conductivity testing method. Although the check-discharge method is accurate in testing the battery capacity, the check-discharge test requires the battery to be fully discharged to the cut-off voltage, which takes a long time and causes a waste of battery energy; the conductivity test method judges the battery by testing the battery conductance (internal resistance). Actual capacity, but only when the battery capacity is less than 50% of the rated capacity, the battery's internal resistance will be in good consistency with the capacity, so the conductivity test cannot fully evaluate the health of the battery.

Therefore, existing detection methods for distribution terminal battery capacity have the disadvantages of long test time, inaccurate test results, and serious waste of battery capacity.

Contents of the invention

The object of the present invention is to provide a distribution terminal battery life detection method and device to solve the problems of existing detection methods with long test time, inaccurate test results, and serious waste of battery capacity.

In a first aspect, according to an embodiment of the present invention, a distribution terminal battery life detection method is provided, including the following steps:

S1. Obtain the terminal voltage at both ends of the detected battery, and determine whether the terminal voltage is greater than the minimum voltage at both ends of the detected battery; if the terminal voltage is less than the minimum voltage, charge the detected battery until the The terminal voltage is greater than the minimum voltage; if the terminal voltage is greater than the minimum voltage, detect the internal resistance of the detected battery;

S2. When the internal resistance detection of the tested battery is completed, perform a discharge test on the tested battery to obtain a short-term discharge curve; including:

S21. Obtain the maximum power of the detection device, the rated capacity and rated voltage of the detected battery, and obtain the discharge current of the detected battery;

S22. When the discharge current detection of the detected battery is completed, obtain the minimum float voltage of the detected battery, and determine the detection initial voltage and detection initial time based on the terminal voltage and the minimum float voltage;

S23. Obtain the terminal voltage drop value of the detected battery, continue to discharge the discharge current in step S21 for 5 minutes, and determine whether the terminal voltage drop value of the detected battery is greater than 20mV. If the terminal voltage drop value is less than 20mV, then continue to discharge the discharge current. If the terminal voltage drop value is greater than 20mV, stop detection, obtain the detection end time and detection end voltage, and obtain the short-term discharge curve;

S3. According to the short-time discharge curve, obtain the slope of the discharge curve;

S4. Obtain the detection reference voltage point according to the detection initial voltage and the detection end voltage;

S5. Obtain the standard discharge curve of the detected battery, and obtain the standard slope according to the voltage of the detected reference voltage point;

S6. According to the rated capacity, the slope of the discharge curve and the standard slope, and according to the capacity calculation formula, obtain an estimated value of the detected battery capacity;

S7. According to the estimated value of the detected battery capacity, perform internal resistance compensation processing on the detected battery to obtain the capacity after internal resistance compensation;

S8. According to the internal resistance compensated capacity and the actual temperature of the detected battery, perform temperature compensation processing on the detected battery to obtain the actual capacity of the detected battery.

Preferably, the step S21 specifically includes:

Obtain the maximum power of the detection device, the rated capacity and the rated voltage of the detected battery, gradually calculate the discharge rate, and obtain the discharge current of the detected battery according to the discharge rate; wherein, the discharge rate of The calculation formula is:

RatedVol×mag×RatedCap/10≤P _max ;

In the formula, RatedVol represents the rated voltage of the battery being tested, RatedCap represents the rated capacity of the battery being tested, P _max represents the maximum power of the detection device, and mag represents the discharge rate;

The calculation formula of the discharge current is:

I=mag×RatedCap/10;

In the formula, I represents the discharge current, RatedCap represents the rated capacity of the battery being tested, and mag represents the discharge rate.

Preferably, the step S22 specifically includes the following steps:

Obtain the minimum float voltage of the detected battery, and determine whether the terminal voltage is greater than the minimum float voltage;

If the terminal voltage is greater than the minimum float voltage, the discharge is continued for 30 seconds according to the discharge current. When the change in the terminal voltage is constant, the discharge is continued for 1.5 minutes. When the terminal voltage is less than the minimum float voltage, the discharge is continued for 30 seconds. When the voltage is high, record the initial detection voltage and the initial detection time;

If the terminal voltage is less than the minimum float voltage, the discharge is continued for 30 seconds according to the discharge current. When the change of the terminal voltage is constant, the detection initial voltage and the detection initial time are recorded.

Preferably, in step S3, the slope of the discharge curve is obtained according to the short-term discharge curve; wherein the calculation formula for the slope of the discharge curve is:

K _t =ΔU/(Time _End - Time _Start );

In the formula, K _t represents the slope of the discharge curve, ΔU represents the terminal voltage drop value, Time _Start represents the detection initial time, and Time _End represents the detection end time.

Preferably, in step S6, the capacity calculation formula of the estimated value of the detected battery capacity is:

C _t =RatedCap×k _r ×mag×(RatedCap/12)/k _t ;

In the formula, RatedCap represents the rated capacity, K _t represents the slope of the discharge curve, K _r represents the standard slope, and mag represents the discharge rate.

Preferably, the step S7 specifically includes:

Increase the cut-off voltage of the battery being tested, and obtain the time when it is consistent with the rated voltage and the time it takes for the rated voltage to drop to 10.5V based on the cut-off voltage, and then based on the capacity of the battery being tested. Estimate the value, perform internal resistance compensation processing on the tested battery, and obtain the capacity after internal resistance compensation; wherein, the calculation formula of the cut-off voltage is:

BatVol _min =10.5×RatedVol/12+BatRes×RatedCap(V);

In the formula, BatVol _min represents the cut-off voltage, RatedVol represents the rated voltage of the tested battery, BatRes represents the internal resistance of the tested battery, and RatedCap represents the rated capacity of the tested battery;

The capacity calculation formula of the internal resistance compensation is: C _tr =C _t ×T _test /T _st ;

In the formula, C _tr represents the capacity after internal resistance compensation, C _t represents the estimated value of the detected battery capacity, T _test represents the time when the compensated cut-off voltage is consistent with the rated voltage, and T _st represents the rated voltage drop. The time elapsed to reach 10.5V.

Preferably, in step S8, the calculation formula of the actual capacity of the detected battery is:

C _e =C _tr /(1+K(T-25));

In the formula, C _e represents the actual capacity of the battery to be detected, C _tr represents the capacity after internal resistance compensation, T represents the actual temperature of the battery to be detected, the unit is °C, K represents the temperature coefficient, K = 0.005 ~ 0.008 /℃.

In the second aspect, according to an embodiment of the present invention, a distribution terminal battery life detection device is provided, including: a main control module, a voltage detection circuit, an internal resistance detection circuit, a communication circuit, an AC current output circuit, and a constant current discharge circuit and lithium battery pack, among which,

The output end of the main control module is connected to the voltage detection circuit, the internal resistance detection circuit, the communication circuit, the AC current output circuit, the constant current discharge circuit and the input end of the lithium battery pack respectively. connected;

The input terminal of the main control module is connected to the voltage detection circuit, the internal resistance detection circuit, the communication circuit, the AC current output circuit, the constant current discharge circuit and the output terminal of the lithium battery pack respectively. connected;

The AC current output circuit includes a power module and a command sending module;

The sending instruction module is used to send control instructions requesting the output of AC current;

The power module is used to output the AC current;

The main control module is used to receive the control instruction and control the power module in the AC current output circuit to output the AC current;

The voltage detection circuit is used to detect the DC voltage at both ends of the detected battery in real time;

The internal resistance detection circuit is used to detect the AC voltage at both ends of the detected battery in real time, and obtain the internal resistance of the detected battery based on the AC current;

The constant current discharge circuit is used to control the detected battery to perform constant current discharge and perform discharge testing;

The communication circuit is used to output detection data, and the detection data includes: the DC voltage, the AC voltage, the AC current and the internal resistance;

The lithium battery pack is used to provide electrical energy.

Preferably, the device further includes a human-computer interaction module, which includes a display unit and an input unit; the display unit and the input unit are respectively connected to the main control module; the display unit is to display the detection data; and the input unit is used to set corresponding working parameters.

Preferably, the device further includes a lithium battery charge and discharge management circuit. The lithium battery charge and discharge management circuit is provided between the lithium battery pack and the main control module. The lithium battery charge and discharge management circuit is respectively connected to the control module. The lithium battery pack is connected to the main control module; the lithium battery charge and discharge management circuit is used to control the charging and discharging of the lithium battery pack.

As can be seen from the above technical solutions, the present invention provides a distribution terminal battery life detection method and device. The method includes the following steps: obtaining the terminal voltage at both ends of the detected battery, determining whether the terminal voltage is greater than the minimum voltage, and detecting the detected battery life. The internal resistance of the battery; when the internal resistance detection is completed, perform a discharge test on the tested battery to obtain a short-term discharge curve, and then obtain the slope of the discharge curve; obtain the detection reference voltage point based on the detection initial voltage and detection end voltage; and obtain The standard discharge curve of the tested battery is used to obtain the standard slope; and then according to the capacity calculation formula, an estimated value of the tested battery capacity is obtained; the tested battery is subjected to internal resistance compensation processing and temperature compensation processing to obtain the actual capacity of the tested battery . The method and device provided by the invention test the actual capacity of the battery to be detected based on short-term discharge of the voltage change rate; first, the internal resistance is measured, and the internal resistance is determined by utilizing the relationship between the capacity of the battery to be detected and the change of the terminal voltage; Then conduct a discharge test, by performing a constant current short-time discharge of 5 to 20 minutes on the tested battery; finally perform a capacity measurement, and estimate the tested battery capacity based on the voltage change rate of the tested battery terminal voltage; this method fully considers the tested battery. Detect the impact of the internal resistance and temperature of the battery on the actual capacity. Compensate the capacity of the battery being tested based on the internal resistance measured by the four-wire AC test method and the on-site temperature of the battery being tested, and then evaluate the health status of the battery being tested. . The method and device provided by the invention have a short test time, do not need to discharge all the power of the battery being tested, reduce the waste of energy, and comprehensively consider the relationship between capacity, temperature, and internal resistance, the capacity test is accurate, and the battery is tested The evaluation of health status is reasonable.

Description of the drawings

In order to explain the embodiments of the present invention or the technical solutions in the prior art more clearly, the drawings needed to be used in the embodiments will be briefly introduced below. Obviously, the drawings in the following description are only some of the drawings of the present invention. Embodiments, for those of ordinary skill in the art, other drawings can also be obtained based on these drawings without exerting creative efforts.

Figure 1 is a flow chart of a distribution terminal battery life detection method provided by an embodiment of the present invention;

Figure 2 is a flow chart of step S2 in Figure 1;

Figure 3 is a schematic structural diagram of a distribution terminal battery life detection device provided by an embodiment of the present invention;

Figure 4 is a structural diagram of an implementation scenario of the battery life detection device for a distribution terminal provided by an embodiment of the present invention.

Detailed ways

The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only some of the embodiments of the present invention, not all of them. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without making creative efforts fall within the scope of protection of the present invention.

Please refer to Figures 1 and 2. In a first aspect, a distribution terminal battery life detection method provided according to an embodiment of the present invention includes the following steps:

S1. Obtain the terminal voltage at both ends of the detected battery, and determine whether the terminal voltage is greater than the minimum voltage at both ends of the detected battery; if the terminal voltage is less than the minimum voltage, charge the detected battery until the The terminal voltage is greater than the minimum voltage; if the terminal voltage is greater than the minimum voltage, detect the internal resistance of the detected battery;

S2. When the internal resistance detection of the tested battery is completed, perform a discharge test on the tested battery to obtain a short-term discharge curve; including:

S21. Obtain the maximum power of the detection device, the rated capacity and rated voltage of the detected battery, and obtain the discharge current of the detected battery;

S22. When the discharge current detection of the detected battery is completed, obtain the minimum float voltage of the detected battery, and determine the detection initial voltage and detection initial time based on the terminal voltage and the minimum float voltage;

S23. Obtain the terminal voltage drop value of the detected battery, continue to discharge the discharge current in step S21 for 5 minutes, and determine whether the terminal voltage drop value of the detected battery is greater than 20mV. If the terminal voltage drop value is less than 20mV, then continue to discharge the discharge current. If the terminal voltage drop value is greater than 20mV, stop detection, obtain the detection end time and detection end voltage, and obtain the short-term discharge curve;

S3. According to the short-time discharge curve, obtain the slope of the discharge curve;

S4. Obtain the detection reference voltage point according to the detection initial voltage and the detection end voltage;

S5. Obtain the standard discharge curve of the detected battery, and obtain the standard slope according to the voltage of the detected reference voltage point;

S6. According to the rated capacity, the slope of the discharge curve and the standard slope, and according to the calculation formula, obtain an estimated value of the detected battery capacity;

S7. According to the estimated value of the detected battery capacity, perform internal resistance compensation processing on the detected battery to obtain the capacity after internal resistance compensation;

S8. According to the internal resistance compensated capacity and the actual temperature of the detected battery, perform temperature compensation processing on the detected battery to obtain the actual capacity of the detected battery.

Specifically, in step S1, the terminal voltage at both ends of the detected battery is obtained, and it is determined whether the terminal voltage is greater than the lowest voltage at both ends of the detected battery; if the terminal voltage is less than the lowest voltage, then the detected battery is Charging is performed until the terminal voltage is greater than the minimum voltage; if the terminal voltage is greater than the minimum voltage, the internal resistance of the detected battery is detected; and a four-wire AC detection method is used to detect the internal resistance of the detected battery. Resistance is measured.

In the embodiment of the present invention, the battery to be detected is a storage battery as an example. The battery capacity tested in the embodiment of the present invention is a 10h rate capacity, and the tested discharge current DisCur is a multiple of I ₁₀ , recorded as DisCur=mag×I ₁₀ , where mag is the discharge rate, and mag can be 0.1 to 0.9, 1, 2, 3, etc.; as the discharge current increases, the capacity of the battery will decrease. Therefore, the capacity test needs to be converted according to the discharge current. The capacity conversion coefficient is defined as k _c . The embodiment of the present invention is based on relevant standards and information. , when mag=0.1~0.9, take k _c =1, when mag=2, take k _c =0.93, when mag=3, take k _c =0.89.

When testing the life of the battery, it is necessary to detect the actual capacity of the battery, and evaluate the life or health status of the battery based on its actual capacity. To evaluate the quality of a battery is to look at the difference between its actual capacity and its rated capacity. If the actual measured capacity is greater than or equal to its rated capacity, it means the battery has better performance. If the actual measured capacity is much smaller than its rated capacity, the battery is bad. Severe aging. The evaluation is divided into four grades: excellent, good, medium and poor. The percentage of actual capacity and rated capacity is used as the final evaluation score. If the final evaluation score is lower than 60, the actual capacity of the battery is only 60% of the rated capacity of the battery. , it indicates that the detected battery has aged. In order to ensure the normal operation of the on-site equipment, the battery should be replaced in time.

Before testing the battery capacity, the internal resistance of the battery must be measured. When detecting the internal resistance, first determine whether the terminal voltage at both ends of the battery is greater than the minimum voltage of the battery.

Among them, it is known that when the remaining capacity of the battery is less than 50%, the internal resistance of the battery will increase significantly. Considering that the estimated capacity of the battery after short-term discharge needs to be compensated for the internal resistance, the battery internal resistance test is limited The lowest voltage of the battery is the voltage corresponding to 0.5C, and is recorded as BatResVol _min . The lowest voltage of the battery in the embodiment of the present invention is equivalently calculated according to the following formula:

BatResVol _min =12.049×RatedVol/12(V);

In the formula, BatRes Indicates the lowest voltage of the battery, and RatedVol indicates the rated voltage of the battery.

Combined with the requirements of the power distribution terminal for working power, the rated voltage of the battery can be set to 12V, 24V or 48V, etc.

If the terminal voltage of the battery is greater than BatRes When, the internal resistance measurement starts, and the entire test process lasts 5 seconds;

If the terminal voltage of the battery is less than BatRes , the battery needs to be charged until the terminal voltage of the battery is greater than BatRes/> When, the internal resistance of the battery is measured again, and the internal resistance value of the battery is recorded as BatRes.

After the battery internal resistance measurement is completed, ResMesFulfill_Flag is set. If the battery wiring is disconnected during the battery internal resistance test, ResMesFulfill_Flag is set to 0; and after the battery internal resistance test is completed, if the battery wiring is disconnected or the battery is replaced, ResMesFulfill_Flag is all 0.

Determine whether the battery internal resistance measurement completion flag ResMesFulfill_Flag is 1. If ResMesFulfill_Flag is 1, start the capacity test. Otherwise, wait until ResMesFulfill_Flag is 1 before measuring the battery capacity.

In step S2, when the internal resistance detection of the tested battery is completed, a discharge test is performed on the tested battery, and a short-term discharge curve is obtained.

The discharge current is calculated based on the battery parameters set by the human-computer interaction interface and the current terminal voltage of the battery. When calculating the discharge current, it is also necessary to comprehensively consider the maximum power P _max that the detection device can withstand. The specific calculation steps are as follows:

S21. Obtain the maximum power of the detection device, the rated capacity and rated voltage of the detected battery, and obtain the discharge current of the detected battery;

According to the maximum power P _max that the detection device can withstand, the rated capacity of the battery RatedCap and the rated voltage of the battery RatedVol, mag is gradually calculated until mag satisfies the following formula and stops; and according to the discharge rate, the measured battery is obtained Discharge current.

RatedVol×mag×RatedCap/10≤P _max ;

In the formula, RatedVol represents the rated voltage of the battery, RatedCap represents the rated capacity of the battery, P _max represents the maximum power of the detection device, and mag represents the discharge rate.

Among them, when mag < 1, mag increases according to the step size 0.1, when mag ≥ 1, it increases according to the step size 1, and in order to avoid the waste of energy, the maximum value of mag is 3; P _max is taken as 100W.

The minimum float voltage of the battery test is defined as FVol _min . If the terminal voltage of the battery is higher than the float voltage when it starts to discharge, its terminal voltage will drop rapidly. At this time, the voltage change rate of the battery is large, which is a problem for the short-term discharge test of the battery. There is a greater interference; therefore, when calculating the battery's discharge current, it is necessary to determine the relationship between the battery's terminal voltage and the float voltage at this time.

If the terminal voltage of the battery at the beginning of the test is greater than FVol _min , since the battery is lower than FVol _min during the test, the capacity test is more accurate. Therefore, under the condition that the maximum power is met, a larger current (mag≤3) is used for discharge; If the battery voltage at the beginning of the test is less than or equal to FVol _min , under the condition that the maximum power is met, a current of no more than 2I ₁₀ is used to discharge, that is, when mag=3, the value mag=2;

Based on the mag value calculated step by step, the discharge current is calculated according to the following formula.

I=mag×RatedCap/10;

In the formula, I represents the discharge current, RatedCap represents the rated capacity of the battery, and mag represents the discharge rate.

S22. When the discharge current detection of the detected battery is completed, obtain the minimum float voltage of the detected battery, and determine the detection initial voltage and detection initial time based on the terminal voltage and the minimum float voltage;

After the battery's discharge current detection is completed, the initial voltage point of the voltage test must be determined, which includes the following steps:

Obtain the minimum float voltage of the detected battery, and determine whether the terminal voltage is greater than the minimum float voltage;

If the terminal voltage is greater than the minimum float voltage, the discharge is continued for 30 seconds according to the discharge current. When the change in the terminal voltage is constant, the discharge is continued for 1.5 minutes. When the terminal voltage is less than the minimum float voltage, the discharge is continued for 30 seconds. When the voltage is high, record the initial detection voltage and the initial detection time;

If the terminal voltage is less than the minimum float voltage, the discharge is continued for 30 seconds according to the discharge current. When the change of the terminal voltage is constant, the detection initial voltage and the detection initial time are recorded.

Among them, when the discharge current is I ₁₀ , the terminal voltage of the normal capacity will drop to about 2mV×RatedVol/12 within 1.5 minutes. When the capacity drops to 0.3C, the terminal voltage drop value will be greater than 6mV×RatedVol/12. , and the internal resistance of the battery will increase significantly at this time. In this case, the calculation will start when the terminal voltage drops to FVol _min to avoid causing large calculation errors. For this reason, the test starting voltage point can be determined when the voltage drop value satisfies the following formula or the terminal voltage is less than FVol _min . Otherwise, the discharge continues until the above conditions are met, and this moment is recorded as the detection initial time Time _Start , and the voltage is recorded as detection Initial voltage BatBaseVol, the initial detection voltage is the voltage when the voltage change becomes stable after 1.5 minutes of discharge and detection can be started, not the voltage when the detection device just starts to be powered on; among them, if mag<1 in the following formula, then mag is processed as 1;

2mV×RatedVol/12×mag≤ΔU≤6mV×RatedVol/12×mag;

In the formula, ΔU represents the terminal voltage drop value, RatedVol represents the rated voltage of the battery, and mag represents the discharge rate.

S23. Obtain the terminal voltage drop value of the detected battery, continue to discharge the discharge current in step S21 for 5 minutes, and determine whether the terminal voltage drop value of the detected battery is greater than 20mV. If the terminal voltage drop value is less than 20mV, then the discharge current is continuously discharged. If the terminal voltage drop value is greater than 20mV, the detection is stopped, the detection end time and detection end voltage are obtained, and the short-term discharge curve is obtained;

Since the terminal voltage of the battery is greater than the minimum float voltage, the discharge curve characteristics of the battery are difficult to grasp. The voltage drops quickly at the beginning of the test, and then continues at one voltage point for a period of time, or even a brief voltage rise occurs. This phenomenon will cause Failure of capacity testing. Therefore, it is necessary to determine a valid detection initial voltage point, and record its voltage as the detection initial voltage, its time as the detection initial time, the voltage at the end of the test as the detection end voltage BatEndVol, and the time at the end of the test as the detection End time Time _End .

In step S3, obtain the slope of the discharge curve according to the short-term discharge curve;

The calculation formula for the slope of the discharge curve is:

K _t =ΔU/(Time _End - Time _Start );

In the formula, K _t represents the slope of the discharge curve, ΔU represents the terminal voltage drop value, Time _Start represents the detection initial time, and Time _End represents the detection end time.

In step S4, a detection reference voltage point is obtained based on the detection initial voltage and the detection end voltage;

The voltage value BatRefVol of the detection reference voltage point is approximately equivalent to (BatBaseVol+BatEndVol)/2, where BatBaseVol represents the detection initial voltage and BatEndVol represents the detection end voltage.

In step S5, obtain the standard discharge curve of the detected battery, and obtain the standard slope according to the voltage of the detected reference voltage point;

The method provided by the embodiment of the present invention estimates the capacity of the battery by using the voltage change rate, so a standard voltage change rate is needed as a reference. In this embodiment, the battery discharge current is I ₁₀ and the battery rated voltage is 12V. The capacity is the standard discharge curve of the rated capacity as the reference curve. Bring the voltage of the battery's detection reference voltage point into the standard discharge curve to obtain a standard slope K _r . Based on the slope of the discharge curve and the standard slope, estimate the battery capacity and perform a capacity test.

In step S6, according to the rated capacity, the slope of the discharge curve and the standard slope, and according to the calculation formula, an estimated value of the detected battery capacity is obtained;

The calculation formula for the estimated value of the tested battery capacity is:

C _t =RatedCap×k _r ×mag×(RatedCap/12)/k _t ;

In the formula, RatedCap represents the rated capacity, k _t represents the slope of the discharge curve, k _r represents the standard slope, and mag represents the discharge rate.

In the above formula, if mag=0.1~0.9, mag can be approximately taken as 1.

In step S7, based on the estimated value of the detected battery capacity, the internal resistance compensation process is performed on the detected battery to obtain the capacity after internal resistance compensation;

After the battery capacity is estimated, the impact of internal resistance on the actual capacity of the battery should also be considered. Therefore, the method provided by the embodiment of the present invention compensates for the internal resistance. In fact, after considering the influence of internal resistance, the discharge curve of the battery will shift downward as a whole. In order to simplify the calculation, the cut-off voltage of the battery must be increased. The specific steps for internal resistance compensation are as follows:

Increase the cut-off voltage of the tested battery, and based on the cut-off voltage, obtain the time when it is consistent with the rated voltage and the time that elapses when the rated voltage drops to 10.5V, and then based on the estimated value of the tested battery capacity, calculate The tested battery undergoes internal resistance compensation processing to obtain the capacity after internal resistance compensation;

The cut-off voltage of battery discharge is defined as BatVol _min . According to relevant standards and data, the cut-off voltage of the 12V battery in the present invention is set to 10.5V. The calculation formula of the cut-off voltage is:

BatVol _min =10.5×RatedVol/12+BatRes×RatedCap(V);

In the formula, BatVol _min represents the cut-off voltage, RatedVol represents the rated voltage of the battery, BatRes represents the internal resistance of the battery, and RatedCap represents the rated capacity of the battery.

According to the compensated cut-off voltage, after processing it to be consistent with the rated voltage 12V described in the standard discharge curve, a time T _test can be obtained based on this cut-off voltage, and the time that elapses for the voltage in the standard discharge curve to drop to 10.5V is T _test , then the capacity after internal resistance compensation can be calculated as follows:

C _tr =C _t ×T _test /T _st ;

In the formula, C _tr represents the capacity after internal resistance compensation, C _t represents the estimated value of the detected battery capacity, T _test represents the time when the compensated cut-off voltage is consistent with the rated voltage, and T _st represents the rated voltage drop. The time elapsed to reach 10.5V.

In step S8, the actual capacity of the detected battery is obtained based on the internal resistance compensated capacity and the actual temperature of the detected battery.

The battery capacity should also consider the effect of temperature on the actual battery capacity. The calculation formula of the actual battery capacity considering the influence of temperature is:

C _e =C _tr /(1+K(T-25));

In the formula, C _e represents the actual capacity of the battery, C _tr represents the capacity after internal resistance compensation, T represents the actual temperature of the battery in °C, and K represents the temperature coefficient, K=0.005~0.008/℃.

It can be seen from the above technical solution that the distribution terminal battery life detection method provided by the embodiment of the present invention includes the following steps: obtaining the terminal voltage at both ends of the detected battery, determining whether the terminal voltage is greater than the minimum voltage, and detecting the internal resistance of the detected battery; When the internal resistance detection is completed, perform a discharge test on the battery being tested to obtain a short-term discharge curve, and then obtain the slope of the discharge curve; obtain the detection reference voltage point based on the detection initial voltage and detection end voltage; and obtain the standard of the battery being detected The discharge curve is used to obtain the standard slope; and then according to the capacity calculation formula, an estimate of the capacity of the tested battery is obtained; the internal resistance compensation process and temperature compensation process are performed on the tested battery to obtain the actual capacity of the tested battery. The method provided by the invention tests the actual capacity of the battery being detected based on short-term discharge of the voltage change rate; first, the internal resistance is measured, and the internal resistance is determined by utilizing the relationship between the capacity of the battery being detected and the change of the terminal voltage; and then The discharge test is to perform a constant current short-time discharge of the tested battery for 5 to 20 minutes; finally, the capacity is measured, and the tested battery capacity is estimated based on the voltage change rate of the tested battery terminal voltage; this method fully considers the tested battery The influence of the internal resistance and temperature on the actual capacity is compensated based on the internal resistance measured by the four-wire AC test method and the on-site temperature of the battery being tested, and then the health status of the battery being tested is evaluated. The method provided by the invention has a short test time, does not need to discharge all the power of the battery being tested, reduces the waste of energy, and comprehensively considers the relationship between capacity, temperature, and internal resistance, and the capacity test is accurate and is beneficial to the health of the battery being tested. The status evaluation is reasonable.

Please refer to Figures 3 and 4. In a second aspect, an embodiment of the present invention provides a distribution terminal battery life detection device, including: a main control module, a voltage detection circuit, an internal resistance detection circuit, a communication circuit, and an AC current output circuit. , constant current discharge circuit and lithium battery pack, among which,

The output end of the main control module is connected to the voltage detection circuit, the internal resistance detection circuit, the communication circuit, the AC current output circuit, the constant current discharge circuit and the input end of the lithium battery pack respectively. connected;

The input terminal of the main control module is connected to the voltage detection circuit, the internal resistance detection circuit, the communication circuit, the AC current output circuit, the constant current discharge circuit and the output terminal of the lithium battery pack respectively. connected;

The AC current output circuit includes a power module and a command sending module;

The sending instruction module is used to send control instructions requesting the output of AC current;

The power module is used to output the AC current;

The main control module is used to receive the control instruction and control the power module in the AC current output circuit to output the AC current;

The voltage detection circuit is used to detect the DC voltage at both ends of the detected battery in real time;

The internal resistance detection circuit is used to detect the AC voltage at both ends of the detected battery in real time, and obtain the internal resistance of the detected battery based on the AC current;

The constant current discharge circuit is used to control the detected battery to perform constant current discharge and perform discharge testing;

The communication circuit is used to output detection data, and the detection data includes: the DC voltage, the AC voltage, the AC current and the internal resistance;

The lithium battery pack is used to provide electrical energy.

Specifically, the main control module is bidirectionally connected to other modules and circuits in the device to achieve bidirectional communication between detection data and corresponding modules and circuits; the main control module is the core of the distribution terminal battery life detection device, which controls The working status of other modules and circuits; the main control module is also equipped with a communication interface for exporting test data when detecting the battery being tested.

The communication circuit is equipped with 1 network port and 2 serial ports, which can be connected with the communication interface of the main control module to output the detection data of the battery being tested; the communication circuit can also be used by the operator to check the battery through the host computer. The device sets relevant parameters.

The voltage detection circuit is mainly used for real-time monitoring of the DC voltage at both ends of the battery being tested when performing a capacity test on the battery being tested.

The internal resistance detection circuit mainly samples the four-wire AC detection method to measure the internal resistance of the battery being tested. By adding an AC current signal to the battery being tested, the AC voltage at both ends of the battery being tested is measured, and based on the test The data calculates the internal resistance of the battery being tested.

When performing internal resistance testing, it is necessary to first determine whether the terminal voltage of the battery being tested is greater than the minimum voltage of the battery being tested. Only when the terminal voltage is greater than the minimum voltage, the capacity of the battery being tested can be tested.

The AC current output circuit is equipped with a power module and a command sending module, which are used to output AC current for discharge testing.

The AC current output circuit mainly sets the current amplitude, phase and frequency before detection, and sends instructions to the main control module through the sending instruction module. The main control module drives the power module to complete the output of AC current.

The constant current discharge circuit is mainly used to ensure the constant current discharge of the tested battery when calculating the capacity of the tested battery; determine the discharge current based on the parameters set for the tested battery before testing and the status of the tested battery before the discharge test. size, and perform a discharge test based on this constant current. This constant current discharge circuit mainly controls the driving voltage of the MOS tube to make it work in the saturation zone, that is, the constant current zone, thereby achieving constant current discharge.

The lithium battery pack mainly provides electric energy as the power source for the battery life detection work at the inspection site.

Preferably, the detection device further includes a human-computer interaction module, which includes a display unit and an input unit; the display unit and the input unit are respectively connected to the main control module; the display unit is to display the detection data; and the input unit is used to set corresponding working parameters.

Specifically, the human-computer interaction module is composed of a display unit and an input unit. The display unit is an LCD liquid crystal display, which is connected to the main control module through a bus. The detection data of the tested battery are displayed through the display unit; the input unit can be a keyboard. , used to input and set relevant parameters of the detection device, including the detected battery parameters and communication parameters.

Preferably, the detection device further includes a lithium battery charge and discharge management circuit. The lithium battery charge and discharge management circuit is provided between the lithium battery pack and the main control module. The lithium battery charge and discharge management circuit is respectively connected to the control module. The lithium battery pack is connected to the main control module; the lithium battery charge and discharge management circuit is used to control the charging and discharging of the lithium battery pack.

Specifically, the lithium battery charge and discharge management circuit is mainly used to control the charging and discharging of the lithium battery pack, estimate the remaining battery power based on the lithium battery operating current and voltage, and display the remaining power in real time through the display unit.

The working process of each structure of the distribution terminal battery life detection device provided by the embodiment of the present invention, and the functions implemented by each structure can be referred to the distribution terminal battery life detection method provided by the first aspect of the embodiment of the present invention. The process steps will not be repeated here.

As can be seen from the above technical solution, embodiments of the present invention provide a distribution terminal battery life detection method and device. The method includes the following steps: obtaining the terminal voltage at both ends of the detected battery, determining whether the terminal voltage is greater than the minimum voltage, and detecting The internal resistance of the battery being tested; when the internal resistance detection is completed, conduct a discharge test on the battery being tested to obtain a short-term discharge curve, and then obtain the slope of the discharge curve; according to the detection initial voltage and the detection end voltage, the detection reference voltage point is obtained; And obtain the standard discharge curve of the tested battery to obtain the standard slope; then obtain the estimated value of the tested battery capacity according to the capacity calculation formula; perform internal resistance compensation processing and temperature compensation processing on the tested battery to obtain the tested battery's capacity. Actual capacity. The method and device provided by the invention test the actual capacity of the battery to be detected based on short-term discharge of the voltage change rate; first, the internal resistance is measured, and the internal resistance is determined by utilizing the relationship between the capacity of the battery to be detected and the change of the terminal voltage; Then conduct a discharge test, by performing a constant current short-time discharge of 5 to 20 minutes on the tested battery; finally perform a capacity measurement, and estimate the tested battery capacity based on the voltage change rate of the tested battery terminal voltage; this method fully considers the tested battery. Detect the impact of the internal resistance and temperature of the battery on the actual capacity. Compensate the capacity of the battery being tested based on the internal resistance measured by the four-wire AC test method and the on-site temperature of the battery being tested, and then evaluate the health status of the battery being tested. . The method and device provided by the invention have a short test time, do not need to discharge all the power of the battery being tested, reduce the waste of energy, and comprehensively consider the relationship between capacity, temperature, and internal resistance, the capacity test is accurate, and the battery is tested The evaluation of health status is reasonable.

Other embodiments of the invention will be readily apparent to those skilled in the art from consideration of the specification and practice of the invention disclosed herein. This application is intended to cover any variations, uses, or adaptations of the invention that follow the general principles of the invention and include common knowledge or customary technical means in the technical field that are not disclosed in the invention. . It is intended that the specification and examples be considered as exemplary only, with a true scope and spirit of the invention being indicated by the following claims.

It is to be understood that the present invention is not limited to the precise construction described above and illustrated in the accompanying drawings, and that various modifications and changes may be made without departing from the scope thereof. The scope of the invention is limited only by the appended claims.

Claims (7)

1. A method for detecting battery life of a power distribution terminal, which is characterized in that it includes the following steps: S1. Obtain the terminal voltage at both ends of the detected battery, and determine whether the terminal voltage is greater than the minimum voltage at both ends of the detected battery; if the terminal voltage is less than the minimum voltage, charge the detected battery until the The terminal voltage is greater than the minimum voltage; if the terminal voltage is greater than the minimum voltage, detect the internal resistance of the detected battery; S2. When the internal resistance detection of the tested battery is completed, perform a discharge test on the tested battery to obtain a short-term discharge curve; including: S21. Obtain the maximum power of the detection device, the rated capacity and rated voltage of the detected battery, and obtain the discharge current of the detected battery; S22. When the discharge current detection of the detected battery is completed, obtain the minimum float voltage of the detected battery, and determine the detection initial voltage and detection initial time based on the terminal voltage and the minimum float voltage; S23. Obtain the terminal voltage drop value of the detected battery, continue to discharge the discharge current in step S21 for 5 minutes, and determine whether the terminal voltage drop value of the detected battery is greater than 20mV. If the terminal voltage drop value is less than 20mV, then continue to discharge the discharge current. If the terminal voltage drop value is greater than 20mV, stop detection, obtain the detection end time and detection end voltage, and obtain the short-term discharge curve; S3. According to the short-time discharge curve, obtain the slope of the discharge curve; S4. Obtain the detection reference voltage point according to the detection initial voltage and the detection end voltage; S5. Obtain the standard discharge curve of the detected battery, and obtain the standard slope according to the voltage of the detected reference voltage point; S6. According to the rated capacity, the slope of the discharge curve and the standard slope, and according to the capacity calculation formula, obtain an estimated value of the detected battery capacity; S7. According to the estimated value of the detected battery capacity, perform internal resistance compensation processing on the detected battery to obtain the capacity after internal resistance compensation; S8. According to the internal resistance compensated capacity and the actual temperature of the detected battery, perform temperature compensation processing on the detected battery to obtain the actual capacity of the detected battery. 2. The method according to claim 1, characterized in that step S21 specifically includes: Obtain the maximum power of the detection device, the rated capacity and the rated voltage of the detected battery, gradually calculate the discharge rate, and obtain the discharge current of the detected battery according to the discharge rate; wherein, the discharge rate of The calculation formula is: RatedVol×mag×RatedCap/10≤P _max ; In the formula, RatedVol represents the rated voltage of the battery being tested, RatedCap represents the rated capacity of the battery being tested, P _max represents the maximum power of the detection device, and mag represents the discharge rate; The calculation formula of the discharge current is: I=mag×RatedCap/10; In the formula, I represents the discharge current, RatedCap represents the rated capacity of the battery being tested, and mag represents the discharge rate. 3. The method according to claim 1, characterized in that step S22 specifically includes the following steps: Obtain the minimum float voltage of the detected battery, and determine whether the terminal voltage is greater than the minimum float voltage; If the terminal voltage is greater than the minimum float voltage, the discharge is continued for 30 seconds according to the discharge current. When the change in the terminal voltage is constant, the discharge is continued for 1.5 minutes. When the terminal voltage is less than the minimum float voltage, the discharge is continued for 30 seconds. When the voltage is high, record the initial detection voltage and the initial detection time; If the terminal voltage is less than the minimum float voltage, the discharge is continued for 30 seconds according to the discharge current. When the change of the terminal voltage is constant, the detection initial voltage and the detection initial time are recorded. 4. The method according to claim 1, characterized in that, in the step S3, the slope of the discharge curve is obtained according to the short-term discharge curve; wherein the calculation formula of the slope of the discharge curve is: K _t =ΔU/(Time _END - Time _Start ); In the formula, K _t represents the slope of the discharge curve, ΔU represents the terminal voltage drop value, Time _Start represents the detection initial time, and Time _END represents the detection end time. 5. The method according to claim 1, wherein in step S6, the capacity calculation formula of the estimated value of the detected battery capacity is: C _t =RatedCap×k _r ×mag×(RatedCap/12)/K _t ; In the formula, RatedCap represents the rated capacity, K _t represents the slope of the discharge curve, k _r represents the standard slope, and mag represents the discharge rate. 6. The method according to claim 1, characterized in that step S7 specifically includes: Increase the cut-off voltage of the battery being tested, and obtain the time when it is consistent with the rated voltage and the time it takes for the rated voltage to drop to 10.5V based on the cut-off voltage, and then based on the capacity of the battery being tested. Estimate the value, perform internal resistance compensation processing on the tested battery, and obtain the capacity after internal resistance compensation; wherein, the calculation formula of the cut-off voltage is: BatVol _min =10.5×RatedVol/12+BatRes×RatedCap(V); In the formula, BatVol _min represents the cut-off voltage, RatedVol represents the rated voltage of the tested battery, BatRes represents the internal resistance of the tested battery, and RatedCap represents the rated capacity of the tested battery; The capacity calculation formula of the internal resistance compensation is: C _tr =C _t ×T _test /T _st ; In the formula, C _tr represents the capacity after internal resistance compensation, C _t represents the estimated value of the detected battery capacity, T _test represents the time when the compensated cut-off voltage is consistent with the rated voltage, and T _st represents the rated voltage drop. The time elapsed to reach 10.5V. 7. The method according to claim 1, characterized in that, in the step S8, the calculation formula of the actual capacity of the detected battery is: C _e =C _tr /(1+K(T－25)); In the formula, C _e represents the actual capacity of the battery to be detected, C _tr represents the capacity after internal resistance compensation, T represents the actual temperature of the battery to be detected, the unit is °C, K represents the temperature coefficient, K = 0.005 ~ 0.008 /℃.