CN114924201A - A kind of test method of cycle life of lithium iron phosphate battery pack for communication under working condition - Google Patents

Abstract

The invention discloses a working condition cycle life testing method of a lithium iron phosphate battery pack for communication, which comprises the following steps: s1: setting an environmental test chamber; s2: placing the lithium iron phosphate battery pack for communication in a test environment for environmental adaptation for a period of time; s3: charging with 0.5C current CCCV until the voltage reaches 3.6 NV and the current reaches 0.05C; s4: standing for a period of time; s5: 0.5C current CC discharge to voltage 2.7 × N V; s6: standing for a period of time; s7: circulating from the step S3 to the step S6; s8: setting an environmental test chamber; s9: placing the lithium iron phosphate battery pack for communication in a test environment for a period of time for environmental adaptation; s10: float charging, float charging voltage U ₀ N V, time t h; s11: 0.5C current CC discharge to voltage 2.7 × N V; s12: standing for a periodSpacing; s13: circulating from the step S10 to the step S12; s14: circulating from the step S1 to the step S13; the method can well feed back the real service life condition of the lithium iron phosphate battery pack for communication.

Description

A kind of test method of cycle life of lithium iron phosphate battery pack for communication under working condition

technical field

The invention relates to the technical field of lithium batteries, in particular to a method for testing the cycle life of a lithium iron phosphate battery pack for communication under working conditions.

Background technique

In the field of backup power for 5G communications, traditional lead-acid batteries are gradually being replaced by lithium batteries due to their large maintenance workload, short lifespan, and large capacity affected by temperature. Lithium batteries have excellent rate discharge characteristics. Higher energy density, stronger temperature adaptability. At present, the lithium iron phosphate battery pack for communication usually adopts the continuous online floating charging mode, and the lithium iron phosphate battery pack for communication mainly refers to YD/T 2344.1-2011 "Lithium iron phosphate battery pack for communication Part 1: Integrated battery" Group "6.8 for cycle life test, it is impossible to give a good feedback on the real service life of the lithium iron phosphate battery pack for communication, and it is impossible to show the safety of the floating charge of the battery pack in the actual use process.

Invention patent CN113805089A proposes a method and system for estimating the floating charge life of a power lithium battery, including acquiring the floating charge information of the lithium battery to be tested, and the floating charge information includes the temperature, rate, and storage of the lithium battery to be tested during the battery floating charging process. The number of days and the number of cycles; the floating charge information is processed by using a pre-built battery floating charge life degradation estimation model to predict the floating charge life of the lithium battery to be tested. The invention uses the battery floating charge life degradation estimation model to estimate the floating charge life of the power lithium battery in the actual scenario. The accuracy of the model needs to be improved due to the stability and fixedness, and the model estimation cannot truly reflect the safety in the actual use process.

Invention patent CN113219360 A proposes a lithium battery cycle life test method based on a floating charge strategy, including the following steps: S1, charging: charge the battery with a constant current and constant voltage, the upper limit voltage is 4.35V, and the cut-off current is 0.05C; S2: Discharge: discharge the battery with constant current, the lower limit voltage is 3.0V; take S1 to S2 as a cycle, the interval fixed cycle is maintained at 4.35V constant voltage charging for 24h after the charging process is completed, and the cycle ends after 100 times or 1000h . The focus of this invention patent is to develop a method for accelerated testing of lithium battery cycle life, rather than a method for testing cycle life under operating conditions based on actual operating conditions.

Invention patent CN111106404A proposes an optimization method for floating charge of lithium iron phosphate battery. In the process of floating charge cycle of lithium iron phosphate battery, the three-stage charge and discharge method of "ladder charge-float charge-constant current discharge" is adopted to reduce the deterioration of active materials , Improve the cycle life of lithium iron phosphate batteries. The focus of this invention patent is to develop a charging and discharging strategy to prolong the service life of the battery, rather than the direction of the battery life detection method.

SUMMARY OF THE INVENTION

The purpose of the present invention is to provide a method for testing the cycle life of a lithium iron phosphate battery pack for communication under working conditions, so as to solve the problems raised in the above-mentioned background art.

In order to achieve the above purpose, the present invention provides the following technical solutions: a method for testing the cycle life of a lithium iron phosphate battery pack for communication under working conditions, characterized in that: the testing steps of the cycle life under the working conditions include: the test environment temperature is T1～T2 , and T1≤T2;

S1: Set the environmental test box;

S2: Place the lithium iron phosphate battery pack for communication in the test environment for a period of environmental adaptation;

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

S4: stand for a period of time;

S5: 0.5C current CC discharge up to voltage 2.7*N V;

S6: stand for a period of time;

S7: From steps S3 to S6, loop;

S8: Then set the environmental test box;

S9: Place the lithium iron phosphate battery pack for communication in the test environment for a period of time for environmental adaptation;

S10: float charge, float charge voltage U ₀ *NV, time is th;

S11: 0.5C current CC discharge up to voltage 2.7*N V;

S12: stand for a period of time;

S13: From steps S10 to S12, loop;

S14: From steps S1 to S13, loop;

S15: Set the environmental test box again;

S16: Place the lithium iron phosphate battery pack for communication in the test environment for a period of time for environmental adaptation;

S17: 0.5C current CCCV charging, cut-off voltage 3.6*N V, cut-off current 0.05C

S18: Stand for a while

S19: 0.5C current CC discharge, cut-off voltage 2.7*N V

S20: Stand for a while

S21: From steps S17 to S20, a cycle is performed, and the test is ended.

Preferably, T1 and T2 in the S1 are alternately changed according to the interval of 12h, while T1 and T2 are determined according to the environmental characteristics in which the lithium iron phosphate battery pack for communication works;

The environmental test chambers in the steps S1 and S15 are all set to a fixed-value operation mode of 25°C;

The environmental adaptation time in the steps S2 and S16 is not less than 4h;

The standing time in the steps S4, S6, S18 and S20 is all 0.5h;

The number of cycles in the steps S7 and S21 is 3 times, and the average value of the discharge capacity for 3 times is taken, which is denoted as C _n-1 , where n is a positive integer, which can be used to calculate the discharge capacity retention rate, and the calculation formula is η=C _n-1 /C ₀ *100%;

The environmental test chamber in the step S8 is set in the 24h program operation mode of T1~T2~T1;

The environmental adaptation time in the step S9 is not less than 8h;

The standing time in the step S12 is 5h;

The number of cycles in the step S13 is 50;

The number of cycles in the step S14 is 60 times.

Preferably, after the 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. .

Preferably, the C is the rated capacity of the lithium iron phosphate battery pack for communication, generally 20, 50, 100, 150Ah;

The U ₀ is provided by the product manufacturer, and generally takes 3.35~3.4V;

The t is determined by local power conditions;

The N is the number of batteries in series in the product, generally 15 or 16.

Compared with the prior art, the beneficial effects of the present invention are: the present invention can be well tested under conditions that fit the actual working conditions, and through the cycle life test method of the working conditions, the communication function can also be well fed back. The actual service life of the lithium iron phosphate battery pack. In the cycle test in steps S8 to S14, through continuous online floating charging, the safety of floating charging of the battery pack in actual use can also be shown.

Description of drawings

Fig. 1 is a flow chart of a method for testing the cycle life of a lithium iron phosphate battery pack for communication according to the present invention;

FIG. 2 is a cycle life diagram of Embodiment 1 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 a part of the embodiments of the present invention, but not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts shall fall within the protection scope of the present invention.

Please refer to FIG. 1 , the present invention provides a technical solution: a method for testing the cycle life of a lithium iron phosphate battery pack for communication under operating conditions. The steps for testing the cycle life under operating conditions include:

The test environment temperature is T1~T2, and T1≤T2, T1, T2 alternately change according to the interval of 12h, and T1, T2 are determined according to the environmental characteristics of the communication lithium iron phosphate battery pack;

S1: Set the environmental test box to the constant value operation mode of 25°C;

S2: The lithium iron phosphate battery pack for communication is placed in the test environment for environmental adaptation, and the time is not less than 4h;

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

S4: stand for 0.5h

S5: 0.5C current CC discharge up to voltage 2.7*N V

S6: stand for 0.5h

S7: Carry out the cycle, from steps S3 to S6, the number of cycles is 3, and the average value of the discharge capacity of 3 times is recorded as C _n-1 , n is a positive integer, which can be used to calculate the discharge capacity retention rate, and the calculation formula is η = C _{n- 1} /C ₀ *100%;

The above steps S1 to S7 are the initial cycle preprocessing steps.

Then enter the middle cycle processing step, the middle cycle processing step includes:

S8: Set the environmental test box to the 24h program operation mode of T1~T2~T1;

S9: The lithium iron phosphate battery pack for communication is adapted to the environment, and the time is not less than 8h;

S10: float charge, float charge voltage U ₀ *NV, time is th

S11: 0.5C current CC discharge up to voltage 2.7*N V

S12: stand for 5h

S13: Circulate, from S10 to S12 steps, the number of cycles is 50;

And after the end of step S13, the capacity calibration will be performed on the capacitance. The calibration method is to repeat steps S1 to S7, measure the average value of the discharge capacity, and calculate the discharge capacity retention rate. The calculation formula is η= C _n-1 /C ₀ * 100%;

If the battery performance is relatively poor, the η calculated by the above-mentioned intermediate cycle processing steps will be less than or equal to 80%. In this case, the test can be terminated in advance, and the obtained discharge capacity retention rate will be compared with the conventional national standard. Line mark for comparison.

If the performance of the battery is relatively good, the η calculated by the above-mentioned middle cycle treatment step will be greater than or equal to 80%. In this case, the large cycle treatment step will be entered. The large cycle treatment step includes:

S14: Circulate, from steps S1 to S13, the number of cycles is 60;

S15: Set the environmental test box to the constant value operation mode of 25°C;

S16: The lithium iron phosphate battery pack for communication is placed in the test environment for environmental adaptation, and the time is not less than 4h;

S17: 0.5C current CCCV charging, cut-off voltage 3.6*N V, cut-off current 0.05C

S18: stand for 0.5h

S19: 0.5C current CC discharge, cut-off voltage 2.7*N V

S20: stand for 0.5h

S21: Carry out the cycle, from steps S17 to S20, the number of cycles is 3, and the average value of the discharge capacity of 3 times is recorded as C _n-1 , and n is a positive integer, which can be used to calculate the discharge capacity retention rate. The calculation formula is η = C _{n- 1} /C ₀ *100%;

After the large cycle treatment step is completed, the obtained discharge capacity retention rate is compared with the conventional national standard.

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

The U ₀ is provided by the product manufacturer, and generally takes 3.35~3.4V;

The t is determined by local power conditions;

The N is the number of batteries in series in the product, generally 15 or 16.

Example 1

Combining with Figure 2 below, take a set of 48V100Ah lithium iron phosphate battery pack for communication (integrated type), among which, the rated capacity of the lithium iron phosphate battery pack for communication is C=100Ah; U ₀ =3.4V; t=72h; in the product The number of batteries in series, N=16;

The calculation formula used is, discharge capacity retention rate η= C _n-1 /C ₀ *100%, if η is less than or equal to 80%, the test can be terminated in advance;

Then implement the following specific tests:

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

S1: Set the environmental test box to the constant value operation mode of 25°C;

S2: The lithium iron phosphate battery pack for communication is placed in the test environment for environmental adaptation, and the time is not less than 4h;

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

S4: stand for 0.5h;

S5: 50A current CC discharge up to voltage 2.7*16V;

S6: stand for 0.5h;

S7: Carry out the cycle, from steps S3 to S6, the number of cycles is 3, and the average value of the discharge capacity of 3 times is taken as C _n-1 , and n is a positive integer;

S8: Set the environmental test chamber to the 24h program operation mode of 10℃~30℃~10℃;

S9: The lithium iron phosphate battery pack for communication is adapted to the environment, and the time is not less than 8h;

S10: Float charge, the float charge voltage is 3.4*16 V, and the time is 72 h;

S11: 50A current CC discharge up to 2.7*16 V;

S12: stand for 5h;

S13: Circulate, from steps S10 to S12, the number of cycles is 50;

S14: Circulate, from steps S1 to S13, the number of cycles is 60;

S15: Set the environmental test box to the constant value operation mode of 25°C;

S16: The lithium iron phosphate battery pack for communication is placed in the test environment for environmental adaptation, and the time is not less than 4h;

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

S18: stand for 0.5h;

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

S20: stand for 0.5h;

S21: Carry out the cycle, from steps S17 to S20, the number of cycles is 3, and the average value of the discharge capacity of 3 times is taken as C _n-1 , and n is a positive integer;

Put the average value of the capacitance obtained after passing the test of the above steps into the formula η= C _n-1 /C ₀ *100%, and the final discharge capacity retention rate can be compared with the conventional national standard, and you can feedback The actual service life of lithium iron phosphate battery packs for outbound communications.

Although embodiments of the present invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, and substitutions can be made in these embodiments without departing from the principle and spirit of the invention and modifications, the scope of the present invention is defined by the appended claims and their equivalents.

Claims (4)

1. A working condition cycle life test method of a lithium iron phosphate battery pack for communication is characterized by comprising the following steps: the working condition cycle life testing step comprises the following steps: the test environment temperature is T1-T2, and T1 is not more than T2;

s1: setting an environmental test chamber;

s2: placing the lithium iron phosphate battery pack for communication in a test environment for a period of time for environmental adaptation;

s3: charging with 0.5C current CCCV until the voltage reaches 3.6 NV and the current reaches 0.05C;

s4: standing for a period of time;

s5: 0.5C current CC discharge to voltage 2.7 x N V;

s6: standing for a period of time;

s7: circulating from the step S3 to the step S6;

s8: setting an environmental test chamber;

s9: placing the lithium iron phosphate battery pack for communication in a test environment for environmental adaptation for a period of time;

s10: float charging, float charging voltage U ₀ N V, time t h;

s11: 0.5C current CC discharge to voltage 2.7 × N V;

s12: standing for a period of time;

s13: circulating from the step S10 to the step S12;

s14: circulating from the step S1 to the step S13;

s15: setting an environmental test chamber;

s16: placing the lithium iron phosphate battery pack for communication in a test environment for a period of time for environmental adaptation;

s17: 0.5C current CCCV charging, cut off to voltage 3.6 × N V, cut off to current 0.05C

S18: standing for a period of time

S19: 0.5C current CC discharge, cut to voltage 2.7 × N V

S20: standing for a period of time

S21: and (6) circulating from the step S17 to the step S20, and finishing the test.

2. The working condition cycle life test method of the lithium iron phosphate battery pack for communication according to claim 1, characterized in that: t1 and T2 in the S1 respectively alternate at intervals of 12h, and T1 and T2 are determined according to the environmental characteristics of the working position of the lithium iron phosphate battery pack for communication;

the environmental test chamber in the steps S1 and S15 is set to a constant value operation mode at 25 ℃;

the environment adaptation time in the steps S2 and S16 is not less than 4 h;

the standing time in the steps S4, S6, S18 and S20 is 0.5 h;

the cycle times in the steps S7 and S21 are both 3 times, and the average value of the 3 discharge capacities is recorded as C _n-1 Wherein n is a positive integer and can be used for calculating the discharge capacity retention rate, and the calculation formula is eta = C _n-1 /C ₀ *100%；

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

the environment adaptation time in the step S9 is not less than 8 h;

the standing time in the step S12 is 5 h;

the number of cycles in the step S13 is 50;

the number of cycles in step S14 is 60.

3. The working condition cycle life test method of the lithium iron phosphate battery pack for communication according to claim 1, characterized in that: and after the step S13 is finished, carrying out capacity calibration, wherein the calibration mode is to repeat the steps S1-S7, measure the mean value of the discharge capacity and calculate the retention rate of the discharge capacity, and if eta is less than or equal to 80%, the test can be finished in advance.

4. The working condition cycle life test method of the lithium iron phosphate battery pack for communication according to claim 1, characterized in that: the C is the rated capacity of the lithium iron phosphate battery pack for communication, and is generally 20, 50, 100 or 150 Ah;

the U is ₀ The method is provided by a product manufacturer, and generally 3.35-3.4V is taken;

the t is determined by local power conditions;

the number of the batteries in the product in series is generally 15 or 16.

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