A test method for the cycle life of a lithium iron phosphate battery pack for communication

Abstract

The present invention discloses a method for testing the cycle life of a lithium iron phosphate battery pack for communication under working conditions. The testing steps of the cycle life under working conditions include: S1: Set the environmental test chamber; S2: Place the lithium iron phosphate battery pack for communication in the test environment for a period of time for environmental adaptation; S3: Charge with a current of 0.5C in CCCV mode until the voltage reaches 3.6*NV and the current reaches 0.05C; S4: Stand for a period of time; S5: Discharge with a current of 0.5C in CC mode until the voltage reaches 2.7*NV; S6: Stand for a period of time; S7: Repeat steps S3 to S6 in a cycle; S8: Set the environmental test chamber again; S9: Place the lithium iron phosphate battery pack for communication in the test environment again for a period of time for environmental adaptation; S10: Float charge with a voltage of U0*NV for a time of t h; S11: Discharge with a current of 0.5C in CC mode until the voltage reaches 2.7*NV; S12: Stand for a period of time; S13: Repeat steps S10 to S12 in a cycle; S14: Repeat steps S1 to S13 in a cycle. The present invention can well reflect the true service life of the lithium iron phosphate battery pack for communication.

Description

Technical Field

[0001] The present invention relates to the technical field of lithium batteries, and in particular to a method for testing the operating cycle life of a lithium iron phosphate battery pack for communications. Background Art

[0002] In the field of 5G communication backup power supply, traditional lead-acid batteries are gradually being replaced by lithium batteries due to their disadvantages such as large maintenance workload, short life span, and large capacity impact by temperature. Lithium batteries have excellent rate discharge characteristics, higher energy density, and stronger temperature adaptability. At present, lithium iron phosphate battery packs for communication usually adopt continuous online floating charge mode, and the lithium iron phosphate battery packs for communication are currently mainly tested for cycle life with reference to YD / T 2344.1-2011 "Lithium iron phosphate battery packs for communication Part 1: Integrated battery packs" 6.8, which cannot give a good feedback on the actual service life of lithium iron phosphate battery packs for communication, and cannot show the safety of floating charge of battery packs in actual use.

[0003] Invention patent CN113805089A proposes a method and system for estimating the floating charge life of a power lithium battery, including obtaining the floating charge information of the lithium battery to be tested, the floating charge information including the temperature, rate, storage days and cycle number of the lithium battery to be tested during the floating charge process; using a pre-built battery floating charge life degradation estimation model to process the floating charge information and predict the floating charge life of the lithium battery to be tested. This invention uses the battery floating charge life degradation estimation model to estimate the floating charge life of a power lithium battery in actual scenarios. The model is obtained through derivation and calculation, and has not been reversely verified and corrected by the actual working condition life. At the same time, it is limited by the singleness and fixity of the temperature field, so that the accuracy of the model needs to be improved, and the model estimation cannot truly reflect the safety during actual use.

[0004] Invention patent CN113219360 A proposes a lithium battery cycle life test method based on a floating charge strategy, including the following steps: S1, charging: charging the battery with constant current and constant voltage, the upper limit voltage is 4.35V, and the cut-off current is 0.05C; S2: discharging: discharging the battery with constant current, the lower limit voltage is 3.0V; S1 to S2 is a cycle, and the interval is fixed. After the charging process is completed, the constant voltage charging of 4.35V is maintained for 24 hours, and the cycle ends after 100 cycles or 1000 hours. This invention patent focuses on opening up a method for accelerated testing of lithium battery cycle life, rather than a working condition cycle life test method based on actual working conditions.

[0005] Invention patent CN111106404A proposes a floating charge optimization method for lithium iron phosphate batteries. During the floating charge cycle of lithium iron phosphate batteries, a three-stage charging and discharging method of "step charging-floating charging-constant current discharge" is adopted to reduce the degradation of active substances and improve the cycle life of lithium iron phosphate batteries. The invention patent focuses on developing charging and discharging strategies to extend the battery life, rather than the direction of battery life detection methods. Summary of the invention

[0006] The object of the present invention is to provide a method for testing the cycle life of a lithium iron phosphate battery pack for communication in order to solve the problems raised in the above-mentioned background technology.

[0007] To achieve the above object, the present invention provides the following technical solution: a method for testing the working cycle life of a lithium iron phosphate battery pack for communication, characterized in that: the testing steps of the working cycle life include: the test environment temperature is T1~T2, and T1≤T2;

[0008] S1: Set up the environmental test chamber;

[0009] S2: Place the communication lithium iron phosphate battery pack in the test environment for a period of time to adapt to the environment;

[0010] S3: 0.5C current CCCV charging, cut-off voltage 3.6*NV, cut-off current 0.05C;

[0011] S4: Let stand for a while;

[0012] S5: 0.5C current CC discharge cut-off voltage 2.7*NV;

[0013] S6: Let stand for a while;

[0014] S7: loop from S3 to S6;

[0015] S8: Set up the environmental test chamber again;

[0016] S9: placing the communication lithium iron phosphate battery pack in the test environment for a period of time to adapt to the environment;

[0017] S10: Float charge, float charge voltage U0*NV, time th;

[0018] S11: 0.5C current CC discharge cut-off voltage 2.7*NV;

[0019] S12: Let stand for a while;

[0020] S13: loop from step S10 to step S12;

[0021] S14: loop from step S1 to step S13;

[0022] S15: Set up the environmental test chamber again;

[0023] S16: placing the communication lithium iron phosphate battery pack in the test environment for a period of time to adapt to the environment;

[0024] S17: 0.5C current CCCV charging, cut-off voltage 3.6*NV, cut-off current 0.05C

[0025] S18: Let it sit for a while

[0026] S19: 0.5C current CC discharge, cut-off voltage 2.7*NV

[0027] S20: Let it sit for a while

[0028] S21: loop from steps S17 to S20 and end the test.

[0029] Preferably, T1 and T2 in S1 are changed alternately at intervals of 12 hours, and T1 and T2 are determined according to the environmental characteristics of the communication lithium iron phosphate battery pack;

[0030] The environmental test chambers in steps S1 and S15 are both set to a fixed value operation mode of 25°C;

[0031] The environmental adaptation time in steps S2 and S16 is not less than 4 hours;

[0032] The standing time in steps S4, S6, S18 and S20 is 0.5h;

[0033] The number of cycles in steps S7 and S21 is 3, and the average of the 3 discharge capacities is taken and recorded as C n-1 , where n is a positive integer, can be used to calculate the discharge capacity retention rate, the calculation formula is η = C n-1 / C0*100%;

[0034] The environmental test chamber in step S8 is set in a 24-hour program operation mode of T1~T2~T1;

[0035] The environmental adaptation time in step S9 is not less than 8 hours;

[0036] The standing time in step S12 is 5 hours;

[0037] The number of cycles in step S13 is 50 times;

[0038] The number of cycles in step S14 is 60.

[0039] Preferably, after step S13 is completed, capacity calibration is performed, and the calibration method is to repeat steps S1 to S7, measure the average discharge capacity, and calculate the discharge capacity retention rate. If η is less than or equal to 80%, the test can be terminated in advance.

[0040] Preferably, C is the rated capacity of a lithium iron phosphate battery pack for communication, which is generally 20, 50, 100, or 150 Ah;

[0041] The U0 is provided by the product manufacturer and is generally 3.35~3.4V;

[0042] The t is determined by the local power conditions;

[0043] N is the number of batteries connected in series in the product, which is usually 15 or 16.

[0044] Compared with the prior art, the beneficial effects of the present invention are as follows: the present invention can be well tested under conditions that fit the actual working conditions, and through the working condition cycle life test method, it can also well feedback the actual service life of the lithium iron phosphate battery pack for communication. In the cycle test of steps S8~S14, through continuous online floating charging, it can also show the safety of floating charging of grouped batteries during actual use. BRIEF DESCRIPTION OF THE DRAWINGS

[0045] Figure 1 This is a flow chart of the cycle life test method of the lithium iron phosphate battery pack for communication of the present invention;

[0046] Figure 2 This is a cycle life diagram of the first embodiment of the present invention. DETAILED DESCRIPTION

[0047] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0048] See also Figure 1 The present invention provides a technical solution: a method for testing the working cycle life of a lithium iron phosphate battery pack for communication, wherein the testing steps of the working cycle life include:

[0049] The test environment temperature is T1~T2, and T1≤T2. T1 and T2 are changed alternately at intervals of 12 hours. At the same time, T1 and T2 are determined according to the environmental characteristics of the communication lithium iron phosphate battery pack;

[0050] S1: Set the environmental test chamber to a fixed value operation mode of 25°C;

[0051] S2: The communication lithium iron phosphate battery pack is placed in the test environment for environmental adaptation for no less than 4 hours;

[0052] S3: 0.5C current CCCV charging, cut-off voltage 3.6*NV, cut-off current 0.05C

[0053] S4: Stand for 0.5h

[0054] S5: 0.5C current CC discharge cut-off voltage 2.7*NV

[0055] S6: Stand for 0.5h

[0056] S7: Cycle from S3 to S6, the number of cycles is 3, and the average of the three discharge capacities is recorded as C n-1 , n is a positive integer, which can be used to calculate the discharge capacity retention rate. The calculation formula is η = C n-1 / C0*100%;

[0057] The above steps S1 to S7 are initial cycle pretreatment steps.

[0058] Then enter the middle cycle processing step, which includes:

[0059] S8: Set the environmental test chamber to the 24h program operation mode of T1~T2~T1;

[0060] S9: The communication lithium iron phosphate battery pack is adapted to the environment for no less than 8 hours;

[0061] S10: Float charge, float charge voltage U0*NV, time th

[0062] S11: 0.5C current CC discharge cut-off voltage 2.7*NV

[0063] S12: Stand for 5 hours

[0064] S13: loop from step S10 to step S12, the number of loops is 50;

[0065] After step S13 is completed, the capacitance will be calibrated. The calibration method is to repeat steps S1 to S7, measure the average discharge capacity, and calculate the discharge capacity retention rate. The calculation formula is η = C n-1 / C0*100%;

[0066] If the battery performance is relatively poor, the η calculated by the above-mentioned mid-cycle processing step will be less than or equal to 80%. In this case, the test can be terminated early and the obtained discharge capacity retention rate can be compared with the conventional national standard and industry standard.

[0067] If the battery performance is good, the η calculated by the above medium cycle processing step will be greater than or equal to 80%, in which case the large cycle processing step will be entered, and the large cycle processing step includes:

[0068] S14: loop from step S1 to step S13, the number of loops is 60;

[0069] S15: Set the environmental test chamber to a fixed value operation mode of 25°C;

[0070] S16: The communication lithium iron phosphate battery pack is placed in the test environment for environmental adaptation for no less than 4 hours;

[0071] S17: 0.5C current CCCV charging, cut-off voltage 3.6*NV, cut-off current 0.05C

[0072] S18: Stand for 0.5h

[0073] S19: 0.5C current CC discharge, cut-off voltage 2.7*NV

[0074] S20: Stand for 0.5h

[0075] S21: Cycle from S17 to S20, the number of cycles is 3, and the average of the three discharge capacities is recorded as C n-1 , n is a positive integer, which can be used to calculate the discharge capacity retention rate. The calculation formula is η = C n-1 / C0*100%;

[0076] After the large cycle processing step is completed, the obtained discharge capacity retention rate is compared with the conventional national standard and industry standard.

[0077] In the above embodiment, C is the rated capacity of the lithium iron phosphate battery pack for communication, which is generally 20, 50, 100, 150 Ah, etc.;

[0078] The U0 is provided by the product manufacturer and is generally 3.35~3.4V;

[0079] The t is determined by the local power conditions;

[0080] N is the number of batteries connected in series in the product, which is usually 15 or 16.

[0081] Embodiment 1

[0082] Combine the following Figure 2, take a set of 48V100Ah communication lithium iron phosphate battery pack (integrated), where the rated capacity of the communication lithium iron phosphate battery pack is C=100Ah; U0=3.4V; t=72h; the number of batteries in series in the product is N=16;

[0083] The calculation formula used is, discharge capacity retention rate η = C n-1 / C0*100%, if η is less than or equal to 80%, the test can be terminated early;

[0084] Then implement the following specific tests:

[0085] The test environment temperature is T1=10℃, T2=30℃;

[0086] S1: Set the environmental test chamber to a fixed value operation mode of 25°C;

[0087] S2: The communication lithium iron phosphate battery pack is placed in the test environment for environmental adaptation for no less than 4 hours;

[0088] S3: 50A CCCV charging, cut-off voltage 3.6*16V, cut-off current 5A;

[0089] S4: let stand for 0.5h;

[0090] S5: 50A current CC discharge cut-off voltage 2.7*16V;

[0091] S6: let stand for 0.5h;

[0092] S7: Cycle from S3 to S6, the number of cycles is 3, and the average of the three discharge capacities is recorded as C n-1 , n is a positive integer;

[0093] S8: Set the environmental test chamber to a 24-hour program operation mode of 10℃~30℃~10℃;

[0094] S9: The communication lithium iron phosphate battery pack is adapted to the environment for no less than 8 hours;

[0095] S10: Float charge, float charge voltage 3.4*16 V, time 72 h;

[0096] S11: 50A current CC discharge cut-off voltage 2.7*16 V;

[0097] S12: let stand for 5 hours;

[0098] S13: loop from step S10 to step S12, the number of loops is 50;

[0099] S14: loop from step S1 to step S13, the number of loops is 60;

[0100] S15: Set the environmental test chamber to a fixed value operation mode of 25°C;

[0101] S16: The communication lithium iron phosphate battery pack is placed in the test environment for environmental adaptation for no less than 4 hours;

[0102] S17: 50A current CCCV charging, cut-off voltage 3.6*16 V, cut-off current 5A;

[0103] S18: let stand for 0.5h;

[0104] S19: 5A current CC discharge, cut-off voltage 2.7*16V;

[0105] S20: let stand for 0.5h;

[0106] S21: Cycle from S17 to S20, the number of cycles is 3, and the average of the three discharge capacities is recorded as C n-1 , n is a positive integer;

[0107] Put the average capacitance value obtained after the above steps into the formula η = C n-1 / C0*100%, the final discharge capacity retention rate is compared with the conventional national standard and industry standard to provide feedback on the actual service life of the lithium iron phosphate battery pack for communication.

[0108] Although embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that various changes, modifications, substitutions and variations may be made to the embodiments without departing from the principles and spirit of the present invention, and that the scope of the present invention is defined by the appended claims and their equivalents.

Claims

1. A method for testing the cycle life of a lithium iron phosphate battery pack for communication, characterized in that: The test steps of the working condition cycle life include: the test environment temperature is T1~T2, and T1≤T2; S1: Set up the environmental test chamber; S2: Place the communication lithium iron phosphate battery pack in the test environment for a period of time to adapt to the environment; S3: 0.5C current CCCV charging, cut-off voltage 3.6*NV, cut-off current 0.05C; S4: Let stand for a while; S5: 0.5C current CC discharge cut-off voltage 2.7*NV; S6: Let stand for a while; S7: loop from S3 to S6; S8: Set up the environmental test chamber again; S9: placing the communication lithium iron phosphate battery pack in the test environment for a period of time to adapt to the environment; S10: Float charge, float charge voltage U0*N, time th; S11: 0.5C current CC discharge cut-off voltage 2.7*NV; S12: Let stand for a while; S13: loop from step S10 to step S12; S14: loop from step S1 to step S13; S15: Set up the environmental test chamber again; S16: placing the communication lithium iron phosphate battery pack in the test environment for a period of time to adapt to the environment; S17: 0.5C current CCCV charging, cut-off voltage 3.6*NV, cut-off current 0.05C S18: Let it sit for a while S19: 0.5C current CC discharge, cut-off voltage 2.7*NV S20: Let it sit for a while S21: loop from steps S17 to S20 and end the test.

2. A method for testing the cycle life of a lithium iron phosphate battery pack for communication according to claim 1, characterized in that: T1 and T2 in S1 are changed alternately at intervals of 12 hours, and T1 and T2 are determined according to the environmental characteristics of the communication lithium iron phosphate battery pack; The environmental test chambers in steps S1 and S15 are both set to a fixed value operation mode of 25°C; The environmental adaptation time in steps S2 and S16 is not less than 4 hours; The standing time in steps S4, S6, S18 and S20 is 0.5h; The number of cycles in steps S7 and S21 is 3, and the average of the 3 discharge capacities is taken and recorded as C n-1 , where n is a positive integer, can be used to calculate the discharge capacity retention rate, the calculation formula is η = C n-1 / C0*100%; The environmental test chamber in step S8 is set in a 24-hour program operation mode of T1~T2~T1; The environmental adaptation time in step S9 is not less than 8 hours; The standing time in step S12 is 5 hours; The number of cycles in step S13 is 50 times; The number of cycles in step S14 is 60.

3. The method for testing the cycle life of a lithium iron phosphate battery pack for communication according to claim 1, characterized in that: After step S13 is completed, capacity calibration will be performed. The calibration method is to repeat steps S1 to S7, measure the average discharge capacity, and calculate the discharge capacity retention rate. If η is less than or equal to 80%, the test can be terminated in advance.

4. A method for testing the cycle life of a lithium iron phosphate battery pack for communication according to claim 1, characterized in that: C is the rated capacity of the lithium iron phosphate battery pack for communication, which is generally 20, 50, 100, or 150 Ah; The U0 is provided by the product manufacturer and is generally 3.35~3.4V; The t is determined by the local power conditions; N is the number of batteries connected in series in the product, which is usually 15 or 16.

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