Battery state of health estimation method considering battery consistency
Technical Field
The present invention relates to the field of battery state of health detection methods, and in particular, to a battery state of health estimation method that takes into account battery consistency.
Background
Under the influence of energy crisis and environmental crisis, new energy automobiles, especially electric automobiles, have received wide attention from all countries in the world, and lithium batteries are also receiving great attention as the mainstream power source of electric automobiles. The lithium battery monomer is connected in series and parallel to form a battery pack so as to provide a power source for the electric automobile. With the increase of the cycle number and the service time of the lithium battery pack, the lithium battery can be gradually attenuated, and the state estimation and the control strategy of the battery system are influenced. In the prior art, there are generally two ways for estimating the attenuation degree of a lithium battery cell: firstly, an empirical model of battery attenuation is obtained through the relationship between the laboratory measurement cycle number and the service time and the battery attenuation; and the other method is to observe the internal structure and chemical reaction of the battery, obtain parameters such as SEI film and concentration change of active lithium ions, and predict the battery attenuation. However, the two methods are mainly performed for the single battery, in an actual working condition, the working condition and environment change violently, no condition is adopted to observe the internal structure parameters of the battery, and meanwhile consistency among the single batteries is not considered, so that the two estimation methods cannot be directly used for estimating the health state of the lithium battery pack under the actual working condition.
Therefore, the present invention provides a method for estimating state of health of a battery, which is simple and easy to implement, and can estimate the SOH state of the battery more comprehensively and accurately, in consideration of battery consistency.
Disclosure of Invention
In view of the above prior art, an object of the present invention is to provide a method for estimating the state of health of a battery, which is simple and easy to implement, and can estimate the SOH state of the battery more comprehensively and accurately, in consideration of the battery consistency, by overcoming the problems in the prior art that only a single battery is used, the internal structural parameters of the battery are observed without conditions in the actual working conditions, and the consistency among the single batteries is not considered, and the estimation method cannot be directly used for estimating the state of health of the lithium battery pack in the actual working conditions.
In order to achieve the above object, the present invention provides 1 a state of health estimation method of a battery considering battery consistency, characterized in that the state of health estimation method of a battery considering battery consistency includes the steps of:
step 1, judging whether a battery to be detected is in a charging state, and when the battery to be detected is in the charging state, performing step 2; when the battery to be detected is in a non-charging state, skipping to the step 5;
step 2, judging whether the battery to be detected finishes the charging process, and when the battery to be detected finishes the charging, performing step 3; when the battery to be detected does not finish the charging process, skipping to the step 5;
step 3, judging whether the battery to be detected is fully charged, and when the battery to be detected is fully charged, performing step 4; when the battery to be detected is not fully charged, jumping to the step 5;
step 4, calculating the value of SOH1 by the following formula: SOH1 ═ Q ÷ C0, where Q denotes the total rechargeable capacity of the battery pack and C0 is the nominal capacity of the battery;
step 5, the value of SOH1 is not updated, the stored value of SOH1 is adopted, and then step 6 is carried out;
step 6, judging whether the battery to be detected is in a standing process, and if the battery to be detected is in the standing process, performing step 7; if the battery to be detected is in a non-standing state, jumping to the step 9;
step 7, judging the time of the battery to be detected in the standing process, and if the standing time is not less than 2 hours, performing step 8; otherwise, skipping to step 9;
step 8, calculating the value of SOH2 through the following formula, wherein SOH2 is 1- (SOCmax-SOCmin), SOCmax is the state of charge of the battery cell with the highest SOC, and SOCmin is the state of charge of the battery cell with the lowest SOC;
step 9, the value of SOH2 is not updated, and the stored SOH2 value is adopted;
step 10, updating the SOH value of the battery pack according to the SOH1 and SOH2 values obtained in the step 4, the step 5, the step 8 and the step 9; wherein,
the SOH is expressed as the state of health of the battery, the SOH1 is expressed as the influence of the total capacity of the battery on the state of health of the battery, and the SOH2 is expressed as the influence of the consistency of the battery on the state of health of the battery.
Preferably, in step 10, the method for updating SOH includes: when the value of the SOH1 exceeds 90% and the value of the SOH2 also exceeds 90%, the value of the SOH is the arithmetic average of the value of the SOH1 and the value of the SOH 2; otherwise the value of the SOH of the battery pack is the smaller of the value of the SOH1 and the value of the SOH 2.
Preferably, the equation for calculating the value of SOH1 in step 4 may be converted to: SOH1 is Δ Q ÷ (1-SOC0) × C0>, where SOC is the state of charge of the battery, SOC0 is the initial SOC of the battery, and Δ Q is the amount of time change of the battery from the initial SOC to a fully charged state.
Preferably, the initial value of SOH1 and the initial value of SOH2 are both set to 100%.
Preferably, in the step 4 and the step 8, the SOH1 and the SOH2 obtained by each calculation are stored.
Preferably, when the value of SOH exceeds 90%, the state of health of the battery is good; when the value of SOH is less than 90%, the state of health of the battery is deteriorated.
In accordance with the above technical problems, the present invention estimates the state of health of a battery pack by comprehensively considering the full capacity of the battery pack and the consistency of battery cells and characterizing the influence of the battery pack capacity fade and the consistency between battery cells on the state of health of the battery pack, wherein the steps from 1 to 5 are the calculation and update of the SOH1 value of the battery, that is, the calculation of the influence of the total capacity on the state of health of the battery pack, the steps from 6 to 9 are the calculation and update of the SOH2 value of the battery, that is, the calculation of the influence of the battery consistency on the state of health of the battery pack, and then the SOH1 value and the SOH2 value are combined to estimate the state of health of the battery pack, wherein when the battery is in a charging state and has been fully charged and the charging process is finished, a new SOH1 value is calculated by a formula and stored, an old SOH1 value is overwritten, and when the battery is in a standing process for more than 2 hours, the new SOH2 value is calculated by the formula and stored, overwriting the old SOH2 value.
The estimation method is simple and easy to implement, and the health state of the battery pack is estimated more accurately and comprehensively.
Additional features and advantages of the invention will be set forth in the detailed description which follows.
Drawings
The accompanying drawings, which are included to provide a further understanding of the invention and are incorporated in and constitute a part of this specification, illustrate embodiments of the invention and together with the description serve to explain the principles of the invention and not to limit the invention. In the drawings:
fig. 1 is a schematic flow chart diagram of a battery state of health estimation method considering battery consistency according to a preferred embodiment of the present invention.
Detailed Description
The following detailed description of embodiments of the invention refers to the accompanying drawings. It should be understood that the detailed description and specific examples, while indicating the present invention, are given by way of illustration and explanation only, not limitation.
As shown in fig. 1, the present invention provides a state of health estimation method of a battery considering battery consistency, including the steps of:
step 1, judging whether a battery to be detected is in a charging state, and when the battery to be detected is in the charging state, performing step 2; when the battery to be detected is in a non-charging state, skipping to the step 5;
step 2, judging whether the battery to be detected finishes the charging process, and when the battery to be detected finishes the charging, performing step 3; when the battery to be detected does not finish the charging process, skipping to the step 5;
step 3, judging whether the battery to be detected is fully charged, and when the battery to be detected is fully charged, performing step 4; when the battery to be detected is not fully charged, jumping to the step 5;
step 4, calculating the value of SOH1 by the following formula: SOH1 ═ Q ÷ C0, where Q denotes the total rechargeable capacity of the battery pack and C0 is the nominal capacity of the battery;
step 5, the value of SOH1 is not updated, the stored value of SOH1 is adopted, and then step 6 is carried out;
step 6, judging whether the battery to be detected is in a standing process, and if the battery to be detected is in the standing process, performing step 7; if the battery to be detected is in a non-standing state, jumping to the step 9;
step 7, judging the time of the battery to be detected in the standing process, and if the standing time is not less than 2 hours, performing step 8; otherwise, skipping to step 9;
step 8, calculating the value of SOH2 through the following formula, wherein SOH2 is 1- (SOCmax-SOCmin), SOCmax is the state of charge of the battery cell with the highest SOC, and SOCmin is the state of charge of the battery cell with the lowest SOC;
step 9, the value of SOH2 is not updated, and the stored SOH2 value is adopted;
step 10, updating the SOH value of the battery pack according to the SOH1 and SOH2 values obtained in the step 4, the step 5, the step 8 and the step 9; wherein,
the SOH is expressed as the state of health of the battery, the SOH1 is expressed as the influence of the total capacity of the battery on the state of health of the battery, and the SOH2 is expressed as the influence of the consistency of the battery on the state of health of the battery.
In accordance with the above technical problems, the present invention estimates the state of health of a battery pack by comprehensively considering the full capacity of the battery pack and the consistency of battery cells and characterizing the influence of the battery pack capacity fade and the consistency between battery cells on the state of health of the battery pack, wherein the steps from 1 to 5 are the calculation and update of the SOH1 value of the battery, that is, the calculation of the influence of the total capacity on the state of health of the battery pack, the steps from 6 to 9 are the calculation and update of the SOH2 value of the battery, that is, the calculation of the influence of the battery consistency on the state of health of the battery pack, and then the SOH1 value and the SOH2 value are combined to estimate the state of health of the battery pack, wherein when the battery is in a charging state and has been fully charged and the charging process is finished, a new SOH1 value is calculated by a formula and stored, an old SOH1 value is overwritten, and when the battery is in a standing process for more than 2 hours, the new SOH2 value is calculated by the formula and stored, overwriting the old SOH2 value.
In a preferred embodiment of the present invention, the method for updating SOH according to the value of SOH1 and the value of SOH2 in step 10 comprises two cases: the first is that when the value of the SOH1 exceeds 90% and the value of the SOH2 also exceeds 90%, the value of the SOH is the arithmetic mean of the value of the SOH1 and the value of the SOH2, i.e., the sum of the value of the SOH1 and the value of the SOH2 is divided by 2; in the second case, in all cases that do not satisfy the first case, the SOH value of the battery pack is the smaller one of the SOH1 value and the SOH2 value, and then the SOH value is obtained, namely the influence of the state of health of the battery pack, so as to judge the state of health of the battery pack.
In a preferred embodiment of the present invention, the formula for calculating the value of SOH1 in step 4 can be further converted, and the formula for calculating the value of SOH1 in step 4 can be converted into: SOH1 is Δ Q ÷ (1-SOC0) × C0>, where SOC is the state of charge of the battery, SOC0 is the initial SOC of the battery, Δ Q is the amount of time change of the battery from the initial SOC to a full state of charge, C0 is the nominal capacity of the battery,
in the method for estimating state of health of a battery considering battery consistency according to the present invention, if a new SOH1 value and a new SOH2 value are not calculated because conditions are not satisfied at the time of initial use, the initial value of the SOH1 and the initial value of the SOH2 need to be used, and in a preferred embodiment of the present invention, the initial value of the SOH1 and the initial value of the SOH2 are both set to 100%, that is, the battery defaults to the optimal state of health.
In order to make the estimation of the state of health of the battery more comprehensive and accurate, in a preferred embodiment of the present invention, in the step 4 and the step 8, the calculated value of SOH1 and the calculated value of SOH2 are stored each time, and when the battery pack does not meet the requirement of calculating a new SOH1 value in the following detection, the stored value of SOH1 and the stored value of SOH2 are used, so that the accuracy of judging the state of health of the battery pack can be increased.
The state of health of the battery pack can be graded according to the value of the SOH, wherein the grading mode is not specifically required in the present invention, but in order to clearly and intuitively allow people to know the state of health of the battery pack, in a preferred embodiment of the present invention, when the value of the SOH exceeds 90%, the state of health of the battery is defined as good; the state of health of the battery is defined as deterioration when the value of SOH is less than 90%, and the deterioration may be further classified, for example, light deterioration when the value of SOH is less than 90% and greater than 70%, and severe deterioration when the value of SOH is less than 70%.
The preferred embodiments of the present invention have been described in detail with reference to the accompanying drawings, however, the present invention is not limited to the specific details of the above embodiments, and various simple modifications can be made to the technical solution of the present invention within the technical idea of the present invention, and these simple modifications are within the protective scope of the present invention.
It should be noted that the various technical features described in the above embodiments can be combined in any suitable manner without contradiction, and the invention is not described in any way for the possible combinations in order to avoid unnecessary repetition.
In addition, any combination of the various embodiments of the present invention is also possible, and the same should be considered as the disclosure of the present invention as long as it does not depart from the spirit of the present invention.