Method for calculating service life of storage battery

Abstract

The invention provides a storage battery life calculation method which is characterized by comprising the following steps: S1, executing deep discharge on a storage battery pack and recording deep discharge time; when the deep discharge time is less than the determination time, determining that the battery is abnormal; when the deep discharge time is greater than or equal to the judgment time, judging whether the single battery reaches the cut-off voltage of deep discharge or not; if so, respectively calculating the initial SOH value of each single battery in the storage battery pack by using an ampere-hour integral method; if the initial SOH value of a certain battery monomer is greater than 80%, correcting the initial SOH value of the battery monomer according to the difference value between the current voltage and the cutoff voltage of the battery monomer; s2, task scheduling is used, and a deep discharging task is executed on the storage battery pack at a specified periodic moment; if the last deep discharge time does not exceed half a year, continuing to use the last SOH result; and if the deep discharge record does not exist or the last deep discharge record exceeds half a year, executing deep discharge SOH calculation.

Description

Technical Field

[0001] The present invention belongs to the technical field of battery management, and particularly relates to a method for calculating the service life of a storage battery. Background Art

[0002] In power energy storage and backup power systems, as a core component, the performance stability and service life of storage batteries are directly related to the reliability and economy of the systems. With the progress of technology, higher requirements are put forward for battery management, which not only requires real-time monitoring of its basic operating status, but also needs to predict its future performance trends through data analysis to formulate scientific and reasonable operation and maintenance strategies.

[0003] The performance degradation of storage batteries is a complex and slow process, involving the interaction of multiple physical and chemical mechanisms. Traditional operation and maintenance methods often rely on regular inspections and experience judgments, lacking the accurate prediction ability driven by data. Specifically, voltage, internal resistance, and temperature, as indicators directly reflecting the current state of storage batteries, their dynamic changes can reveal the activity degree of internal chemical reactions and the structural integrity of the batteries; while SOC and SOH respectively comprehensively evaluate the performance status of storage batteries from the two dimensions of electricity quantity and health. Combining the historical data of these basic index parameters, especially the number of charge and discharge cycles, alarm events, and their corresponding index change amounts, can further explore the patterns of battery performance degradation and lay a foundation for predicting future states.

[0004] There is a lack of a storage battery life prediction mechanism that combines the above indicators and historical data in the existing technology. It is difficult to optimize operation and maintenance decisions based on experience alone, resulting in difficulties in improving the operation and maintenance efficiency and safety of the overall system. Summary of the Invention

[0005] In view of the problems mentioned in the background art, the present invention proposes a method for calculating the service life of a storage battery, aiming to achieve a refined battery life cycle management solution by monitoring the key indicators of the storage battery in combination with historical charge and discharge data, alarm records, and index change amounts. The specific technical content is as follows:

[0006] A method for calculating the service life of a storage battery, characterized by comprising:

[0007] S1, the SOH calculation step under deep discharge conditions;

[0008] Set the cut-off voltage and determination time for deep discharge, perform deep discharge on the battery pack, and record the deep discharge time;

[0009] When the deep discharge time is less than the determination time, it is determined that the battery is abnormal, and a signal indicating battery replacement is given;

[0010] When the deep discharge time is greater than or equal to the determination time, it is judged whether the single battery has reached the cut-off voltage of deep discharge; if so, the initial SOH values of each battery cell in the battery pack are calculated respectively using the ampere-hour integration method;

[0011] The initial SOH value is the ratio of the discharge capacity SOC of the battery cell to the reference capacity of the battery; that is,

[0012] Initial SOH value = Discharge capacity SOC / Battery reference capacity;

[0013] The ampere-hour integration method calculates the discharge capacity SOC by accumulating the integral of the battery current, and the formula is:

[0014] SOC = SOC0 - (∫Idt / C);

[0015] Where: SOC is the state of charge of the battery, which refers to the ratio of the remaining capacity of the battery to its total capacity; SOC0 is the initial state of charge; I is the battery charge and discharge current; t is the charge and discharge time; C is the total capacity of the battery;

[0016] If there is a situation where the initial SOH value of a certain battery cell is greater than 80%, then according to the difference between the current voltage of the battery cell and the cut-off voltage, its initial SOH value is corrected;

[0017] The correction formula is: SOH = (Current voltage - Cut-off voltage) / (Float charge voltage - Cut-off voltage) * 100%;

[0018] S2. Task scheduling SOH calculation steps;

[0019] Using task scheduling, perform a deep discharge task on the battery pack at a specified periodic moment, and record the historical data of each deep discharge;

[0020] Obtain the most recent (float charge / equalizing charge) historical data;

[0021] If the previous deep discharge time does not exceed half a year, continue to use the previous SOH result;

[0022] If there is no deep discharge record or the previous deep discharge record exceeds half a year, perform a deep discharge SOH calculation to obtain the following three results:

[0023] Result A: The proportion K1 of the single cell SOH* in the most recent (float charge / equalizing charge) historical data;

[0024] Result B: ((Number of days from the current time to the commissioning time) / (Number of days from the battery life time to the current time)) * Proportion K2;

[0025] Result C: Judge whether the voltage of the battery cell exceeds the reference voltage difference;

[0026] If the voltage of the battery cell exceeds the reference voltage difference and the voltage of the battery pack exceeds the reference voltage difference, then, result C = proportion K3 * (voltage difference / reference voltage difference);

[0027] If the voltage of the battery cell does not exceed the reference voltage difference, then result C is assigned the proportion K3;

[0028] That is to say, the result

[0029] The above proportions K1, K2, and K3 are set according to the calculation requirements;

[0030] The final SOH = result A + result B + result C.

[0031] Compared with the prior art, the advantages of the present invention are reflected in: by monitoring the key indicators of the battery, combining historical charge and discharge data, alarm records, and the change amount of indicators, a refined battery life cycle management method is established. This method combines multiple factors such as deep discharge records, ampere-hour integration method, battery operation time, and voltage difference, and can more accurately evaluate the health status of the battery pack. Through practical application verification, this method has high accuracy and reliability in evaluating the battery SOH, accurately judges whether the battery needs to be replaced, provides the remaining life prediction for the batteries that do not need to be replaced immediately, and gives specific replacement time suggestions for the batteries that need to be replaced, providing strong support for the maintenance and management of the battery system, so as to optimize the operation and maintenance decision-making, reduce unnecessary cost expenditures, and improve the operation and maintenance efficiency and safety of the overall system. Specific embodiments

[0032] The following further describes the solution of the present application:

[0033] A battery life calculation method is a comprehensive SOH calculation method based on factors such as deep discharge records, ampere-hour integration method, battery operation time, and voltage difference, which can more accurately evaluate the health status of a lithium-ion battery pack. The specific steps of this method include:

[0034] S1, the SOH calculation steps under deep discharge conditions;

[0035] Set the cut-off voltage and determination time for deep discharge (usually set to 3 minutes), perform deep discharge on the battery pack, and record the deep discharge time;

[0036] 1) When the deep discharge time is less than 3 minutes, it is determined that the battery is abnormal, and a signal to replace the battery is given;

[0037] 2) If the deep discharge time is greater than or equal to 3 minutes, then determine whether the single cell has reached the cut-off voltage for deep discharge; if so, use the ampere-hour integration method to calculate the preliminary SOH value of each battery cell in the battery pack respectively;

[0038] The preliminary SOH value is the ratio of the discharge capacity SOC of the battery cell to the reference capacity of the battery; that is, preliminary SOH value = discharge capacity SOC / reference capacity of the battery;

[0039] The ampere-hour integration method calculates the discharge capacity SOC by accumulating the integral of the battery current, and the formula is:

[0040] SOC = SOC0 - (∫Idt / C); where: SOC is the state of charge of the battery, which refers to the ratio of the remaining capacity of the battery to its total capacity; SOC0 is the initial state of charge; I is the battery charge and discharge current; t is the charge and discharge time; C is the total capacity of the battery; the ampere-hour integration method calculates the real-time SOC of the battery by monitoring the battery current in real time and performing integral operation on it. This calculation is simple and easy to implement and does not require additional voltage measurement; the ampere-hour integration method has high requirements for current accuracy and is prone to cumulative errors, and needs to be calibrated regularly to correct the errors;

[0041] 3) If there is a situation where the preliminary SOH value of a certain battery cell is greater than 80%, then correct its preliminary SOH value according to the difference between the current voltage of this battery cell and the cut-off voltage. The correction formula used is: SOH = (current voltage - cut-off voltage) / (float charge voltage - cut-off voltage) * 100%.

[0042] S2. Task scheduling SOH calculation steps;

[0043] Use task scheduling to perform a deep discharge task on the battery pack at a specified periodic moment (for example, execute the task at 3:33 am every Wednesday and Saturday), and record the historical data of each deep discharge;

[0044] Obtain the most recent (float charge / equalizing charge) historical data;

[0045] If the previous deep discharge time does not exceed half a year, then continue to use the previous SOH result;

[0046] If there is no deep discharge record or the previous deep discharge record exceeds half a year, then perform a deep discharge SOH calculation to obtain the following three results:

[0047] 1) Result A: The proportion K1 of the single cell SOH* in the most recent (float charge / equalizing charge) historical data;

[0048] Among them, the single-cell SOH refers to the health state of a single battery cell, which can usually be evaluated by the ratio of the actual capacity of the battery to the rated capacity. For example, if the current capacity of a certain single battery cell is 80% of its initial capacity, then the SOH of this single cell can be considered 0.8; and the proportion K1 can be set according to the calculation requirements, with a default value of 0.4;

[0049] That is to say, result A = 0.4 * the single-cell SOH in the most recent (float charge / equalizing charge) historical data.

[0050] 2) Result B: ((the number of days from the current time to the commissioning time) / (the number of days from the battery life time to the current time)) * proportion K2; among them,

[0051] a) The difference between the current time and the commissioning time: that is, the number of days from the commissioning of the battery to the current time;

[0052] b) The battery life time: The battery life times of different types of batteries are different. Generally, the life of lead-acid batteries is about 3 - 5 years, and the life of lithium batteries is about 5 - 10 years, etc.;

[0053] c) The number of days of the current time: refers to the number of days from the commissioning of the battery to the current time.

[0054] d) The proportion K2 can be set according to the calculation requirements, with a default value of 0.3;

[0055] That is to say, result B = 0.3 * (the current time - the commissioning time) / (the battery life time - the current time).

[0056] 3) Result C: Determine whether the voltage of the battery single cell exceeds the reference voltage difference;

[0057] If the voltage of the battery single cell exceeds the reference voltage difference and the voltage of the battery pack exceeds the reference voltage difference, then,

[0058] Result C = proportion K3 * (voltage difference / reference voltage difference);

[0059] If the voltage of the battery single cell does not exceed the reference voltage difference, then result C is assigned the value of proportion K3;

[0060] Reference voltage difference: The error between the current single-cell voltage and this result is within 1.0V; the proportion K3 can be set according to the calculation requirements, with a default value of 0.3;

[0061] That is to say, the result

[0062] The final SOH = result A + result B + result C.

[0063] By deeply analyzing the key parameters during the operation of the battery and their historical change trends, this method aims to reveal the internal law of battery performance degradation and provide a more scientific and quantitative decision-making basis for operation and maintenance personnel. For batteries with good performance, a life prediction model is established based on the SOH data curve to estimate their remaining service life, providing a basis for long-term operation and maintenance planning; for batteries whose performance has deteriorated to the critical point, according to the deterioration rate of indicators and safety thresholds, the urgency of replacement is finely divided, and suggestions for immediate replacement or replacement within the next few months (such as within three months) are put forward. This data-driven operation and maintenance strategy can not only effectively avoid system downtime caused by sudden battery failures, but also avoid waste of resources caused by premature replacement, achieving the optimization of battery life cycle management.

[0064] The above preferred implementation manners should be regarded as illustrative examples of the implementation manners of the solution of this application. All technical deductions, replacements, improvements, etc. that are identical, similar to or based on this application solution should be regarded as within the protection scope of this patent.

Claims

1. A method for calculating battery life, characterized in that: include: S1, SOH calculation steps under deep discharge conditions; Set the cut-off voltage and judgment time for deep discharge, perform deep discharge on the battery pack, and record the deep discharge time; When the deep discharge time is less than the determination time, the battery is determined to be abnormal and the intention to replace the battery is expressed; When the deep discharge time is greater than or equal to the judgment time, it is determined whether the single battery has reached the deep discharge cut-off voltage; if reached, the preliminary SOH value of each battery cell in the battery pack is calculated using the ampere-hour integration method; The preliminary SOH value is the ratio of the discharge capacity SOC of the battery cell to the battery reference capacity; Right now, Preliminary SOH value = discharge capacity SOC / battery base capacity; The ampere-hour integration method calculates the discharge capacity SOC by accumulating the integral of the battery current. The formula is: SOC = SOC0 - (∫Idt / C); Among them: SOC is the state of charge of the battery, which refers to the ratio of the remaining capacity of the battery to its total capacity; SOC0 is the initial state of charge; I is the battery charge and discharge current; t is the charge and discharge time; C is the total capacity of the battery; If the preliminary SOH value of a battery cell is greater than 80%, the preliminary SOH value is corrected according to the difference between the current voltage and the cut-off voltage of the battery cell; Correction formula: SOH = (current voltage - cut-off voltage) / (float charge voltage - cut-off voltage) * 100%; S2, task scheduling SOH calculation step; Use task scheduling to perform deep discharge tasks on the battery pack at specified periodic times and record historical data of each deep discharge; Get the most recent (floating charge / equalizing charge) historical data; If the last deep discharge time is less than half a year, the last SOH result will continue to be used; If there is no deep discharge record or the last deep discharge record is more than half a year ago, perform a deep discharge SOH calculation to obtain the following three results: Result A: The monomer SOH* ratio in the most recent (floating charge / equalizing charge) historical data is K1; Result B: ((current time - commissioning time) days / (battery life time - current time) days) * proportion K2; Result C: Determine whether the voltage of the battery cell exceeds the reference voltage difference; If the voltage of the battery cell exceeds the reference voltage difference and the voltage of the battery pack exceeds the reference voltage difference, then the result C = proportion K3*(voltage difference / reference voltage difference); If the battery cell voltage does not exceed the reference voltage difference, the result C is assigned a proportion K3; That is to say, the result The above proportions K1, K2 and K3 are set according to the calculation requirements; Final SOH = result A + result B + result C.

2. The method for calculating battery life according to claim 1, characterized in that: The determination time is set to 3 minutes.

3. The method for calculating battery life according to claim 1, characterized in that: The proportion K1 defaults to 0.4, the proportion K2 defaults to 0.3, and the proportion K3 defaults to 0.3.

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