Battery health degree capacity estimation method
Technical Field
The invention belongs to the technical field of battery state monitoring and estimation, and particularly relates to a method for estimating the state of health (SOH) capacity of a battery.
Background
With the development of new energy industry, more and more users use electric vehicles. The accuracy of the estimation of the SOH state of a power battery, which is the most expensive device on a vehicle, is of exceptional importance. The life of the battery can be estimated by utilizing the SOH of the battery.
The current mainstream methods for calculating the SOH of the battery are an ampere-hour integration method and a cycle period number method.
The cycle count method counts the cycle of the battery, and when the number of cycles of the battery reaches a certain range, it is considered that the battery has reached the end of its service life. The method does not consider the influence of factors such as different cycle conditions, cycle states and the like on the cycle life, and the battery life is determined according to experience and standard parameters.
The ampere-hour integration method is to calculate the residual capacity of the current battery according to the integration of charging data, and then calculate the SOH of the current battery according to the ratio of the residual capacity to the rated capacity.
Therefore, the problem of the prior art is that under the condition of low-precision and low-frequency data, the SOH value is difficult to accurately calculate, and the calculated SOH value has high dispersion degree, so that the difficulty is caused for the future prediction. The existing method for estimating the SOH of the battery cannot meet the use condition that the data precision is not high, and various different conditions cannot be fully considered.
Disclosure of Invention
The invention aims to provide a battery health degree capacity estimation method which is suitable for low data precision and fully considers the influence of different circulation conditions on the service life of a battery.
In order to achieve the purpose, the invention adopts the technical scheme that:
a method for estimating the capacity of the health degree of a battery is used for estimating the capacity of the health degree of the battery to be estimated, and comprises the following steps:
step 1: setting p ambient temperatures and q charge and discharge currents, wherein the charge and discharge currents are expressed by the product of a charge current multiplying power and the rated capacity of the battery; taking a plurality of batteries with the same type as the battery to be estimated, dividing the batteries into p × q groups, wherein each group of batteries corresponds to one ambient temperature and one charge-discharge current;
step 2: carrying out a cyclic charge and discharge experiment on the battery according to the corresponding environment temperature and the charge and discharge current, recording the residual capacity of the battery after each cyclic charge and discharge, and stopping the cyclic charge and discharge experiment when the residual capacity of the battery reaches the lower limit of the residual capacity;
and step 3: fitting to obtain a relation function Cycle of the Cycle times of the battery, the ambient temperature and the charging current multiplying power according to the data obtained by the cyclic charge-discharge experimentT,n=f(T,n);
And 4, step 4: using said relation function Cycle
T,nCalculating the temperature T of the battery to be estimated at the environment as f (T, n)
0Charging current multiplying power n corresponding to charging and discharging current
0Number of cycles of hour
And then calculating the health degree capacity value of the battery to be estimated
Wherein i
0=n
0C is the charge-discharge current of the battery to be estimated, C is the rated capacity of the battery to be estimated, t is the charge-discharge time of the battery to be estimated, t is
startIs the charge-discharge start time t of the battery to be estimated
currThe unit of the SOH value of the health degree capacity of the battery to be estimated is 100 percent for the charging and discharging end time of the battery to be estimated.
In the step 1, the number of the batteries in each group is at least 3.
And in each group of batteries, taking the residual capacity average value of each battery as the residual capacity data of the group of batteries.
In the step 3, the relation function Cycle is obtained by polynomial fittingT,n=f(T,n)。
In the step 4, the method also calculates
The above-mentioned
In the step 1, 4 environmental temperatures are set, which are 0 ℃, 10 ℃, 20 ℃ and 50 ℃.
In the step 1, 3 charging and discharging currents are set, wherein the charging and discharging currents are 0.5C, 1C and 2C respectively.
In the step 2, the lower limit of the remaining capacity is 80% of a rated capacity of the battery.
Due to the application of the technical scheme, compared with the prior art, the invention has the following advantages: the method is suitable for low-precision and low-frequency data, calculates the SOH of the battery based on the low-frequency data, can reflect the influence of different factors on the attenuation of the battery, and is easy to expand.
Drawings
Fig. 1 is a flowchart of a method for estimating the capacity of the health degree of a battery according to the present invention.
Detailed Description
The invention will be further described with reference to examples of embodiments shown in the drawings to which the invention is attached.
The first embodiment is as follows: as shown in fig. 1, a method for estimating the capacity of battery health degree includes the following steps:
step 1: p (p is a positive integer) ambient temperatures T and q (q is a positive integer) charge and discharge currents i are set, wherein the charge and discharge currents i are expressed by the product of a charge current multiplying power n and a rated capacity C of the battery. A plurality of batteries with the same type as the battery to be estimated are taken, the batteries are divided into p × q groups, and each group of batteries corresponds to an ambient temperature T and a charging and discharging current i.
For example, in this step, 4 ambient temperatures T, T respectively, are set1=0℃、T2=10℃、T320 ℃ and T4Setting 3 charging and discharging currents i as i at 50 DEG C1=0.5C、i21C and i32C. The cells are divided into 12 groups, and the number of cells in each group is at least 3, so that 36 cells are required at least.
Step 2: and carrying out a cyclic charge-discharge experiment on the batteries according to the corresponding ambient temperature and charge-discharge current, recording the residual capacity of the batteries in sequence after each cyclic charge-discharge, and taking the average value of the residual capacity of each battery as the residual capacity data of the battery group because each group comprises a plurality of batteries. The cyclic charge and discharge experiment was stopped when the remaining capacity of the battery reached the remaining capacity lower limit (for example, the remaining capacity lower limit was 80% of the rated capacity of the battery).
And step 3: obtaining a relation function Cycle of the Cycle times of the battery, the ambient temperature and the charging current multiplying power by polynomial fitting according to data obtained by a Cycle charge-discharge experimentT,nF (T, n), wherein,
and 4, step 4: using a relationship function Cycle
T,nCalculating the temperature T of the battery to be estimated at the environment
0Charge and discharge current i
0Corresponding charging current multiplying power n
0Number of cycles of hour
When the charge and discharge t of the battery is to be estimated,
corresponding to
(the unit is 100%), calculating the health capacity value of the battery to be estimated
(unit is 100%) where i
0=n
0C is the charge and discharge current of the battery to be estimated, C is the rated capacity of the battery to be estimated, t is the charge and discharge time of the battery to be estimated, t
startTo be estimated, the charge-discharge start time of the battery, t
currFor the battery to be estimatedThe charge/discharge end time of (1).
The advantages of the above scheme are: 1. the influence of different current sizes and different temperatures on the attenuation of the battery can be reflected; 2. the method is suitable for low-precision and low-frequency data; 3. and can be expanded by the same method if other factors need to be considered.
The above embodiments are merely illustrative of the technical ideas and features of the present invention, and the purpose thereof is to enable those skilled in the art to understand the contents of the present invention and implement the present invention, and not to limit the protection scope of the present invention. All equivalent changes and modifications made according to the spirit of the present invention should be covered within the protection scope of the present invention.