A method for estimating remaining charging time of power battery

Abstract

The present invention provides a method for estimating the remaining charging time based on a temperature rise model. At the beginning of charging, the temperature rise during the charging process is estimated using the temperature rise model. During the charging process, the estimated temperature rise is corrected in real time according to the actual temperature rise. At the same time, the aging state is taken into account, which can greatly improve the accuracy of the remaining charging time estimation, and also improve customer satisfaction and enhance the competitiveness of the product.

Description

Technical Field

[0001] The present invention relates to the field of new energy electric vehicles, in particular to a method and system for estimating the remaining charging time during the charging process of a power battery of an electric vehicle. Background Art

[0002] As the use of electric vehicles increases, charging issues are also attracting more and more attention from users. Due to the characteristics of electric vehicle batteries, it takes a long time to charge the battery. Therefore, displaying an accurate remaining charging time is very helpful to improve user experience and satisfaction. At present, the remaining charging time estimation method used by most vehicles on the market is simply based on different orders of current for calculation, or takes into account temperature rise but cannot be updated in real time, and does not take into account the aging of the battery cells, resulting in a large deviation between the estimated remaining charging time and the actual charging result, which reduces the user experience.

[0003] The prior art discloses a method for estimating the charging time of a power battery, including dividing the battery charging process into multiple charging stages, obtaining charging information at different charging stages, obtaining the voltage-charge state curve of the battery at different temperatures, obtaining the initial state information of the battery when it starts charging, obtaining the temperature rise of the battery at each charging stage, obtaining the charge amount of the battery at each charging stage, calculating the charging time of each stage, and obtaining the total charging time. This method calculates the temperature rise at the beginning, but does not take into account the difference between the theoretical calculated temperature rise and the actual battery temperature rise. There is no real-time correction during the calculation process, resulting in a certain error in the calculation of the charging time. At the same time, this method does not take into account the impact of the reduction in battery capacity after battery aging, which will also lead to an increase in errors.

[0004] There is another method for estimating the remaining charging time, including: determining the charging request current and the corresponding battery temperature change rate; estimating the first estimated time value required for the battery to charge from the state of charge estimation starting value to the upper limit value of the corresponding state of charge estimation interval; estimating the second estimated time value required for the battery to change from the temperature estimation starting value to the upper limit value of the corresponding temperature estimation interval; determining a new state of charge estimation starting value, a new state of charge estimation interval, a new temperature estimation starting value, and a new temperature estimation interval, until the upper limit value of the corresponding state of charge estimation interval is the target state of charge, and the smaller estimated time value is the estimated first estimated time value; accumulating each smaller estimated time value obtained to obtain the remaining charging estimated time value for charging the battery to the target state of charge. This method will recalculate each time the estimated upper limit temperature is reached, and the calculated temperature is not updated in real time, resulting in a certain deviation in the time estimation.

[0005] There is also a charging time estimation method that takes temperature rise into consideration, including: obtaining the current remaining battery power through BMS; dividing the battery charging into several stages, and obtaining the initial charging temperature of the first stage through BMS; obtaining the temperature rise of each stage, thereby calculating the initial charging temperature of each stage; obtaining the maximum current allowed for charging based on the initial charging temperature of each stage; calculating the charging time of each stage based on the maximum current; adding up the power-on time of each stage to obtain the overall charging time. This method uses a fixed value when considering temperature rise, and does not use a temperature rise model. In actual environments, as the battery ages, the temperature rise calculated by the fixed value will be significantly different from the actual temperature rise, resulting in a high error in charging time estimation. In addition, the absence of real-time updates will further increase the error in estimated time. Summary of the invention

[0006] In view of the above shortcomings of the prior art, the present invention provides a method for estimating the remaining charging time of a power battery, which effectively improves the estimation accuracy of the remaining charging time and provides user experience.

[0007] In order to achieve the above object, the present invention provides the following technical solutions:

[0008] The present invention provides a method for estimating the remaining charging time of a power battery, comprising the following steps:

[0009] Step 1: Calculate the initial remaining charging time t 0 :

[0010] After entering the charging mode, the BMS collects various parameters in the current state, including the ambient temperature T envir , Maximum single cell voltage U maxc , minimum single cell voltage U minc , Maximum battery temperature T maxc , minimum battery temperature T minc ; According to the highest single cell voltage U maxc Determine the current battery stage k, and according to the battery charging strategy table, look up the table to determine the corresponding demand current I in the current stage state k , and calculate the charging time t of this stage k ; will t k Substitute it into the temperature rise model to obtain the temperature T of each monomer at the end of this stage cell(j,k) ; Select the highest temperature of all monomer temperatures as the initial temperature T of the next stage maxk , in the k+1th order according to T maxk and the required current I determined by the battery charging strategy table k+1 , calculate the predicted time t k+1 And bring it into the temperature rise model to calculate the temperature T at the end of this stage cell(j,k+1) , and the highest temperature of this stage is used as the initial temperature T of the next stagemax(j,k+1) , and so on, until the full charge voltage or full charge SOC is reached, the initial remaining charging time t is obtained. 0 =t k +t k+1 +……+t n .

[0011] Step 2: Calculate the remaining charging time t in real time:

[0012] During the charging process, the BMS collects the battery voltage, temperature and current current in real time. If the current state meets the maximum single cell voltage U max ≥Cut-off voltage U ter And it lasts for a certain time, which is determined according to the battery performance. The time for different batteries is slightly different, generally <1s, then the charging is completed and the remaining charging time t=0; if it is not satisfied, the actual maximum temperature T at the current moment is determined maxa The temperature T predicted by the temperature rise model maxk If they are the same, the remaining charging time t is calculated according to the initial remaining charging time calculation method in step 1; if they are not the same, the estimated temperature is corrected according to the current actual maximum temperature, that is, the predicted temperature T maxk , bring it into the temperature rise model for recalculation, and update all temperatures in the subsequent stages and recalculate the remaining charging time until charging is completed. In this process, when the actual temperature changes, it will be judged and calculated once, and updated in real time to ensure that the theoretical calculated temperature is the same as the actual temperature, maximizing the estimation accuracy.

[0013] Furthermore, in the above estimation method, the charging strategy table is formulated according to the charging stage and temperature. Different current values ​​correspond to different charging stages and temperatures. The strategy table is used for current query when calculating the remaining charging time. The charging stage divides the charging process into multiple charging segments, i.e., k stages. Different batteries can be set to different values. Each charging segment is a stage, and constant current charging is performed within a stage.

[0014] It can be seen from the above technical solutions that the remaining charging time estimation method based on the temperature rise model provided by the present invention, at the beginning of charging, uses the temperature rise model to estimate the temperature rise during the charging process, and at the same time, the estimated temperature rise is corrected in real time according to the actual temperature rise during the charging process, while taking into account the aging state, which greatly improves the accuracy of the remaining charging time estimation, and also improves customer satisfaction and enhances the competitiveness of the product.

[0015] The charging involved in the present invention is not limited to AC charging or DC charging, and is applicable at different temperatures. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1A schematic diagram of the remaining charging time calculation logic of the present invention;

[0017] Figure 2 The logic diagram of the remaining charging time calculation process of the present invention is updated. DETAILED DESCRIPTION

[0018] In order to facilitate the relevant technical personnel in the field to better understand the scheme of the present invention, the present invention will be described in detail below with reference to the accompanying drawings. The description content is relatively detailed and complete, but it cannot be understood as limiting the scope of the patent of the present invention. For those skilled in the art, obvious variations and other replacement forms based on the following embodiments of the present invention belong to the protection scope of the present invention.

[0019] Embodiment 1:

[0020] In order to implement the method described in the present invention, it is necessary to first formulate a charging strategy table and store it in the controller in advance. The table is as follows:

[0021] The charging process is divided into multiple charging segments (k stages, which can be set to different values ​​for different batteries), each charging segment is a stage, and constant current charging is performed within a stage.

[0022] A charging strategy table is formulated according to the charging stage and temperature. Different current values ​​correspond to different charging stages and temperatures. The strategy table is used for current query for remaining charging time calculation. The table format is as follows;

[0023] Table 1

[0024]

[0025] The above table is only an example table, and the corresponding relationship between the demand current, temperature and order in the present invention is not limited to the example in Table 1.

[0026] Embodiment 2:

[0027] See also Figure 1 and Figure 2 , the method for estimating the remaining charging time of the multi-power battery in this embodiment is described in detail:

[0028] After the user plugs in the gun, the BMS identifies the charging mode based on the collected CC resistance value and enters the charging process. The BMS collects various parameters in the current state, including the ambient temperature T envir , Maximum single cell voltage U maxc , minimum single cell voltage U minc , Maximum battery temperature T maxc , minimum battery temperature T minc Use the highest voltage to determine the current battery stage, and according to the battery charging strategy table, look up the table to determine the corresponding demand current I under the current stage statek , and predict the calculation time t k :

[0029] t k =(SOC k -SOC c )·Cap / I k

[0030] Among them, SOC c Indicates the SOC value in the current state; SOC k Indicates the SOC value corresponding to the end of this stage; Cap is the battery capacity (capacity is multi-dimensional, and the battery capacity is different at different mileages to ensure high estimation accuracy after aging), I k is the demand current in this stage.

[0031] Then, the calculated tk is brought into the temperature rise model to obtain the temperature T of each monomer at the end of this stage. cell(j,k) Select the highest temperature of all monomer temperatures as the initial temperature T of the next stage maxk , the initial temperature T maxk The calculation formula is:

[0032] T maxk =max(T cell(1，k) ,T cell(2，k) , ..., T cell(m，k) ).

[0033] Then, in the k+1th order, according to T maxk and the battery charging strategy table to determine the required current I k+1 , calculate the predicted time t k+1 And bring it into the temperature rise model to calculate the temperature T at the end of this stage cell(j,k+1) ,

[0034]

[0035] Among them, β, γ, and σ are dimensionless parameters or multidimensional arrays, which are optimized with the battery material and aging degree. By taking batteries with different temperatures and different aging degrees for charging tests in the initial stage, the β, γ, and σ values ​​are obtained by fitting according to the actual temperature rise in each stage; dt k is the time required to charge from the kth stage to the k+1th stage; R represents the internal resistance of the monomer; T envir Indicates ambient temperature; T cell(j,k) It represents the temperature of the jth monomer at the kth stage, 1≤j≤m (m is the total number of monomers), 1≤j≤n (n is the total number of current charging stages).

[0036] At the same time, the highest temperature of this stage is taken as the initial temperature T of the next stage. max(j,k+1), and so on, until the full charge voltage or full charge SOC is reached, then the initial remaining charging time displayed is the sum of the charging time calculated in each stage, that is, t 0 =t k +t k+1 +……+t n .

[0037] The above is the remaining charging time estimation method based on the temperature rise model proposed in this paper. It should be noted that any obvious replacement without departing from the concept of the present invention is within the protection scope of the present invention.

Claims

1. A method for estimating the remaining charging time of a power battery, characterized in that: Includes steps: Step 1, calculate the initial display remaining charging time t0: After entering the charging mode, the BMS collects various parameters in the current state, including the ambient temperature T envir , Maximum single cell voltage U maxc , minimum single cell voltage U minc , Maximum battery temperature T maxc , minimum battery temperature T minc ; Determine the current battery stage k based on the highest single cell voltage, and determine the corresponding demand current I in the current stage based on the battery charging strategy table k , and calculate the charging time t of this stage k ; will t k Substitute it into the temperature rise model to obtain the temperature T of each monomer at the end of this stage cell(j,k) ; Select the highest temperature of all monomer temperatures as the initial temperature T of the next stage maxk , in the k+1th order according to T maxk and the required current I determined by the battery charging strategy table k+1 , calculate the predicted time t k+1 And bring it into the temperature rise model to calculate the temperature T at the end of this stage cell(j,k+1) , and the highest temperature of this stage is used as the initial temperature T of the next stage max(j,k+1) , and so on, until the full charge voltage or full charge SOC is reached, the initial remaining charging time t0=t k +t k+1 +……+t n ; The temperature rise model is: Among them, β, γ, and σ are dimensionless parameters or multidimensional arrays, which are related to the battery material and aging degree. By taking batteries with different temperatures and different aging degrees for charging tests in the initial stage, the β, γ, and σ values ​​are obtained by fitting according to the actual temperature rise in each stage; dt k is the time required to charge from the kth stage to the k+1th stage; R represents the internal resistance of the monomer; T envir Indicates ambient temperature; T cell(j,k) represents the temperature of the jth monomer at the kth stage, 1≤j≤m, m is the total number of monomers, 1≤k≤n, n is the total number of current charging stages; Step 2: Calculate the remaining charging time t in real time: During the charging process, the BMS collects the battery voltage, temperature and current current in real time. If the current state meets the maximum single cell voltage U max ≥Cut-off voltage U ter If the temperature is not satisfied, the actual maximum temperature T at the current moment is determined. maxa The temperature T predicted by the temperature rise model maxk Are they the same? If they are the same, calculate the remaining charging time t according to the initial display remaining charging time calculation method in step 1; If they are different, the estimated temperature is corrected according to the current actual maximum temperature, that is, the predicted temperature T maxk , bring it into the temperature rise model for recalculation, and at the same time update all temperatures in the subsequent stages and recalculate the remaining charging time until charging is completed.

2. The remaining charging time estimation method according to claim 1, characterized in that: The charging strategy table is formulated according to the charging stage and temperature. Different current values ​​correspond to different charging stages and temperatures. The strategy table is used for current query when calculating the remaining charging time. The charging stage divides the charging process into multiple charging segments, i.e., k stages. Different batteries can be set to different values. Each charging segment is a stage, and constant current charging is performed within a stage.

3. The remaining charging time estimation method according to claim 1 or 2, characterized in that: The time t k The calculation formula is: Among them, SOC c Indicates the SOC value in the current state; SOC k Indicates the SOC value corresponding to the end of this stage; Cap is the battery capacity, I k is the demand current in this stage.

4. The method for estimating the remaining charging time according to claim 1 or 2, characterized in that: The initial temperature T maxk The calculation formula is: 。

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