A State of Charge Estimation Method of Lithium-Ion Battery Based on Fused Open Circuit Voltage Curve

Round 1

Reviewer 1 Report

This manuscript is very written and has positive contributions to Lithium ion battery modeling. I would suggest to publish after very minor revisions:

Line 41-42. How flat the OCV curve is depends on the chemistry system. e.g., LFP cathode has a flat curve, but LCO is not. So please change the sentence to “However, for some chemistry system like LFP-cathode and graphite-anode, the OCV curves between 10% and 90% SOC range is very flat”. Line 84-85. Please change to “In a lithium-ion battery, the lithium ions are intercalated and de-intercalated in positive and negative electrodes; the amount of lithium ions that are involved determines the capacity, and the potential difference between positive and negative electrodes determines the cell voltage.  Line 86/87, please change to “and the electrolyte allows the lithium ions to move between these two electrodes”.

Author Response

Response to Reviewer 1 Comments

 

Thank you for your careful read and thoughtful comments on the previous draft. These comments are all valuable and very helpful for revising and improving my paper, as well as the important guiding significance to my researches. The response to your comments are as follows:

 

Point 1:  Line 41-42. How flat the OCV curve is depends on the chemistry system. e.g., LFP cathode has a flat curve, but LCO is not. So please change the sentence to “However, for some chemistry system like LFP-cathode and graphite-anode, the OCV curves between 10% and 90% SOC range is very flat”.

 

Response 1: Thank you for your correction, we have revised the sentence according to your suggestion .

 

Point 2:  Line 84-85. Please change to “In a lithium-ion battery, the lithium ions are intercalated and de-intercalated in positive and negative electrodes; the amount of lithium ions that are involved determines the capacity, and the potential difference between positive and negative electrodes determines the cell voltage.

 

Response 2: Thank you for your correction, we have revised the sentence according to your suggestion .

 

Point 3:  Line 86/87, please change to “and the electrolyte allows the lithium ions to move between these two electrodes”.

 

Response 3: Thank you for your correction, we have revised the sentence according to your suggestion .

 

Thanks again for your valuable comments. Never hesitate to point it out if any problem is found during the review,  and we will take the revision seriously.

 

Thanks

 

Sincerely

 

 

Author Response File: Author Response.pdf

Reviewer 2 Report

This manuscript entitled in “A state of charge estimation method of lithium-ion 2 battery based on fused open circuit voltage curve” describes newly developed OCV curve fusion method based on the increment test and low current test for the SOC estimation in lithium-ion batteries. The authors applied neural network algorithm to fit the fusion data set and achieved accurate and robust SOC estimation. All results demonstrate here seems to be solid and their findings will contribute to develop the lithium-ion battery manager system. The authors described the interpretation of their experimental results and their advantages comparing to previous works, via citing many references. This logical description contributes to help reader’s understanding. The reviewer recommends that this manuscript can be accepted for publication in “Applied science” after responding to the minor corrections described below.

Table 1

Nominal Capacity description must be 700 mAh. Please add “h” after 700mA.

    ２．Page 4, 126

The reviewer does not think that your cathode material is LiFePO₄ based on average working voltage and charge profiles. Charge profile strongly implies your cathode material is LiCoO₂ or LiNi_1/3Co_1/3Mn_1/3O₂. Please check again.

Page 4, 133

700ma → 700mA

Dynamic discharge test

The reviewer does not understand the details and meaning of the discharge current profiles. Please add short description on this matter.

Cyclability

All lithium ion batteries commercialized in the world must be degraded during cycling. All lithium-ion batteries commercialized around the world always degrade through charge-discharge cycles. This degradation introduces a new polarization factor in the electrode. Can the proposed SOC control system compensate for changes in electrode characteristics as a function of cycles?

Author Response

Response to Reviewer 2 Comments

 

Thank you for your careful read and thoughtful comments on the previous draft. These comments are all valuable and very helpful for revising and improving my paper, as well as the important guiding significance to my researches. We have studied comments carefully and have made corrections.  The response to your comments are as follows:

 

Point 1:  Table 1

Nominal Capacity description must be 700 mAh. Please add “h” after 700mA.

 

Response 1: Thank you for your correction, we have modified this error.

 

Point 2: Page 4, 126

The reviewer does not think that your cathode material is LiFePO4 based on average working voltage and charge profiles. Charge profile strongly implies your cathode material is LiCoO2 or LiNi1/3Co1/3Mn1/3O2. Please check again.

 

Response 2: Thank you for your correction, we have confirmed with the battery manufacturer that the cathode material is LiCoO2, and we have revised in our manuscript.

 

Point 3: Page 4, 133

700ma → 700mA

 

Response 3: Thank you for your correction, we have modified this error.

 

Point 4: Dynamic discharge test

The reviewer does not understand the details and meaning of the discharge current profiles. Please add short description on this matter.

 

Response 4: The added description is as follows, which is in line 118 through 121 of the revised paper.

“ The dynamic discharge process is set to continuously discharge at 700 mA for 200 seconds, 500 mA for 100 seconds, 100 mA for 100 seconds, 400 mA for 100 seconds, 50 mA for 100 seconds and 200 mA for 100 seconds. The relaxation time is set 2 hours. The dynamic test stops when the cell reaches the discharge cutoff voltage in the last constant discharge process and then relax for 2 hours. ”

 

Point 5: Cyclability

All lithium ion batteries commercialized in the world must be degraded during cycling. All lithium-ion batteries commercialized around the world always through charge-discharge cycles. This degradation introduces a new polarization factor in the electrode. Can the proposed SOC control system compensate for changes in electrode characteristics as a function of cycles?

 

Response 5: We are appreciative of your suggestion. The proposed SOC estimation method contains online model parameter identification, which can be applied to the situation of batteries degrade. However, it has been shown in some literatures that the OCV curve will also change with the battery degrade, so the OCV curve needs to be compensated during the cycles. Our method does not contain this part at present, but the high precision OCV curve obtained by the proposed method is the basis of the following research. We will improve the proposed method in our future study, and the prospect of future research in the conclusion section .

 

Thanks again for your valuable comments. Never hesitate to point it out if any problem is found during the review,  and we will take the revision seriously.

 

Thanks

 

Sincerely

Author Response File: Author Response.pdf