Figure 1.
A 12S28P LiNiCoAlO2 (NCA) series/parallel battery pack for frequency regulation energy storage system (FRESS).
Figure 1.
A 12S28P LiNiCoAlO2 (NCA) series/parallel battery pack for frequency regulation energy storage system (FRESS).
Figure 2.
Discharging/charging current profile for the aging and experimental voltages of the fresh 12S28P NCA series/parallel battery pack: (a) discharging/charging current profile for aging, and (b) experimental discharging/charging voltage.
Figure 2.
Discharging/charging current profile for the aging and experimental voltages of the fresh 12S28P NCA series/parallel battery pack: (a) discharging/charging current profile for aging, and (b) experimental discharging/charging voltage.
Figure 3.
Difference in 12 cell voltages of each representative cell, measured using a voltage sensor, in the fresh battery pack consisting 28 parallel-connected cells according to the discharging/charging current profile for aging (4C-rate).
Figure 3.
Difference in 12 cell voltages of each representative cell, measured using a voltage sensor, in the fresh battery pack consisting 28 parallel-connected cells according to the discharging/charging current profile for aging (4C-rate).
Figure 4.
Difference in 12 cell voltages of each representative cell, measured using a voltage sensor, in the retired series/parallel battery pack consisting of 28 parallel-connected cells according to the discharging/charging current profile for aging (1C-rate).
Figure 4.
Difference in 12 cell voltages of each representative cell, measured using a voltage sensor, in the retired series/parallel battery pack consisting of 28 parallel-connected cells according to the discharging/charging current profile for aging (1C-rate).
Figure 5.
Experimental apparatus for the aging cycle test of the NCA cell.
Figure 5.
Experimental apparatus for the aging cycle test of the NCA cell.
Figure 6.
Aging cycle test of the NCA cell considering a 1C-rate (100 times) and its experimental result (capacity degradation): (a) basic discharging/charging current profile for aging (CC-CV), and (b) capacity degradation considering a 1C-rate (100 times).
Figure 6.
Aging cycle test of the NCA cell considering a 1C-rate (100 times) and its experimental result (capacity degradation): (a) basic discharging/charging current profile for aging (CC-CV), and (b) capacity degradation considering a 1C-rate (100 times).
Figure 7.
Experimental apparatus for the aging cycle test of the NCA cell.
Figure 7.
Experimental apparatus for the aging cycle test of the NCA cell.
Figure 8.
Smoothing of the IC curve using a low-pass filter (LPF).
Figure 8.
Smoothing of the IC curve using a low-pass filter (LPF).
Figure 9.
Discharging/charging voltages of 12 cells in the retired series/parallel battery pack, especially in the narrowed operating voltage range.
Figure 9.
Discharging/charging voltages of 12 cells in the retired series/parallel battery pack, especially in the narrowed operating voltage range.
Figure 10.
IC curve and three detailed peak points and two valley points of the fresh cell no. 1 according to the aging cycle test.
Figure 10.
IC curve and three detailed peak points and two valley points of the fresh cell no. 1 according to the aging cycle test.
Figure 11.
IC variation with respect to the cycle and discharge capacity at IC curve valley point 1 according to the aging cycle test (no. 1 cell): (a) cycle and (b) discharge capacity.
Figure 11.
IC variation with respect to the cycle and discharge capacity at IC curve valley point 1 according to the aging cycle test (no. 1 cell): (a) cycle and (b) discharge capacity.
Figure 12.
Variation in partial capacity with respect to the cycle and discharge capacity in the short voltage range (3.6–3.7 V) according to the aging cycle test on the no. 1 cell: (a) cycle and (b) discharge capacity.
Figure 12.
Variation in partial capacity with respect to the cycle and discharge capacity in the short voltage range (3.6–3.7 V) according to the aging cycle test on the no. 1 cell: (a) cycle and (b) discharge capacity.
Figure 13.
IC variation with respect to the SOH according to the IC curve valley point 1 (no. 1 cell): (a) experimental IC curve valley point 1, and (b) comparison between the linear regression model and experimental IC curve valley point 1 (R2 = 0.9774).
Figure 13.
IC variation with respect to the SOH according to the IC curve valley point 1 (no. 1 cell): (a) experimental IC curve valley point 1, and (b) comparison between the linear regression model and experimental IC curve valley point 1 (R2 = 0.9774).
Figure 14.
Variation in the partial capacity with respect to the SOH according to the IC curve valley point 1 in the short voltage range (3.6–3.7 V) (no. 1 cell): (a) experimental IC curve valley point 1, and (b) comparison between the linear regression model and experimental IC curve valley point 1 (R2 = 0.9849).
Figure 14.
Variation in the partial capacity with respect to the SOH according to the IC curve valley point 1 in the short voltage range (3.6–3.7 V) (no. 1 cell): (a) experimental IC curve valley point 1, and (b) comparison between the linear regression model and experimental IC curve valley point 1 (R2 = 0.9849).
Figure 15.
Block diagram of the linear regression model-based SOH estimation.
Figure 15.
Block diagram of the linear regression model-based SOH estimation.
Figure 16.
Comparison between the linear regression model based on the IC curve peak point of cell no. 1 and a real SOH based on two IC curve peak points of cell nos. 2 and 3.
Figure 16.
Comparison between the linear regression model based on the IC curve peak point of cell no. 1 and a real SOH based on two IC curve peak points of cell nos. 2 and 3.
Figure 17.
Comparison between the linear regression model based on the partial capacity of cell no. 1 and a real SOH based on two partial capacities of cell nos. 2 and 3.
Figure 17.
Comparison between the linear regression model based on the partial capacity of cell no. 1 and a real SOH based on two partial capacities of cell nos. 2 and 3.
Figure 18.
Comparison of four SOH errors (SOH error = Real SOH − Model SOH): (1) between the linear regression model SOH (cell no. 1) and the real SOH (cell nos. 2 and 3) considering the IC curve peak points, and (2) between the linear regression model SOH (cell no. 1) and a real SOH (cell nos. 2 and 3) considering partial capacities.
Figure 18.
Comparison of four SOH errors (SOH error = Real SOH − Model SOH): (1) between the linear regression model SOH (cell no. 1) and the real SOH (cell nos. 2 and 3) considering the IC curve peak points, and (2) between the linear regression model SOH (cell no. 1) and a real SOH (cell nos. 2 and 3) considering partial capacities.
Figure 19.
IC curve valley point 1 of the 12 series-connected stage of the retired series/parallel battery pack.
Figure 19.
IC curve valley point 1 of the 12 series-connected stage of the retired series/parallel battery pack.
Figure 20.
Disassembling of the retired series/parallel battery pack.
Figure 20.
Disassembling of the retired series/parallel battery pack.
Figure 21.
Discharge capacity and SOH of the 12 series-connected stages of the disassembled retired series/parallel battery pack using a full discharge/charge test (7S series stage of the short circuit): (a) discharge capacity and (b) SOH.
Figure 21.
Discharge capacity and SOH of the 12 series-connected stages of the disassembled retired series/parallel battery pack using a full discharge/charge test (7S series stage of the short circuit): (a) discharge capacity and (b) SOH.
Figure 22.
Comparison between the linear regression model based on the IC curve peak point of cell no. 1 and a real SOH based on the IC curve peak point of the 12 series-connected stages of the retired series/parallel battery pack.
Figure 22.
Comparison between the linear regression model based on the IC curve peak point of cell no. 1 and a real SOH based on the IC curve peak point of the 12 series-connected stages of the retired series/parallel battery pack.
Figure 23.
Comparison between the linear regression model based on the partial capacity of cell no.1 and a real SOH based on the partial capacity of the 12 series-connected stages of the retired series/parallel battery pack.
Figure 23.
Comparison between the linear regression model based on the partial capacity of cell no.1 and a real SOH based on the partial capacity of the 12 series-connected stages of the retired series/parallel battery pack.
Figure 24.
Comparison of two SOH errors (SOH error = Real SOH − Model SOH) between the linear regression model SOH (cell no. 1) and a real SOH (12 series-connected stages of the retired series/parallel battery pack) considering the IC curve peak point and partial capacity.
Figure 24.
Comparison of two SOH errors (SOH error = Real SOH − Model SOH) between the linear regression model SOH (cell no. 1) and a real SOH (12 series-connected stages of the retired series/parallel battery pack) considering the IC curve peak point and partial capacity.
Figure 25.
SOH of the retired cell according to the 1C-rate CC-CV aging cycle test (600 times).
Figure 25.
SOH of the retired cell according to the 1C-rate CC-CV aging cycle test (600 times).
Figure 26.
Comparison between the linear regression model based on the IC curve peak point of cell no. 1 cell and a real SOH based on the IC curve peak point of the retired cell.
Figure 26.
Comparison between the linear regression model based on the IC curve peak point of cell no. 1 cell and a real SOH based on the IC curve peak point of the retired cell.
Figure 27.
Comparison between the linear regression model based on the partial capacity of cell no. 1 and a real SOH based on the partial capacity of the retired cell.
Figure 27.
Comparison between the linear regression model based on the partial capacity of cell no. 1 and a real SOH based on the partial capacity of the retired cell.
Table 1.
Numerical results for the comparison between the linear regression model based on the IC curve peak point of cell no. 1 and a real SOH based on two IC curve peak points of cell nos. 2 and 3 cells (SOH error = Real SOH − Model SOH).
Table 1.
Numerical results for the comparison between the linear regression model based on the IC curve peak point of cell no. 1 and a real SOH based on two IC curve peak points of cell nos. 2 and 3 cells (SOH error = Real SOH − Model SOH).
Cell | Cell No. 2 SOH Information | Cell No. 3 SOH Information |
---|
Cycle | Real SOH | Model SOH | SOH Error (%) | Real SOH | Model SOH | SOH Error (%) |
---|
1 | 0.965090 | 0.966002 | 0.091231 | 0.990165 | 0.985305 | 0.486000 |
10 | 0.957525 | 0.954704 | 0.282094 | 0.981765 | 0.976040 | 0.572500 |
20 | 0.950520 | 0.946948 | 0.357228 | 0.975020 | 0.965249 | 0.977100 |
30 | 0.944530 | 0.937065 | 0.746517 | 0.969385 | 0.964879 | 0.450600 |
40 | 0.939880 | 0.936145 | 0.373453 | 0.964180 | 0.956211 | 0.796900 |
50 | 0.934080 | 0.929440 | 0.464022 | 0.959385 | 0.952479 | 0.690600 |
60 | 0.930230 | 0.926427 | 0.380269 | 0.955105 | 0.948051 | 0.705400 |
70 | 0.925500 | 0.922225 | 0.327511 | 0.950895 | 0.941757 | 0.913800 |
80 | 0.921900 | 0.921174 | 0.072571 | 0.947160 | 0.940725 | 0.643500 |
90 | 0.918015 | 0.915819 | 0.219630 | 0.943325 | 0.939466 | 0.385900 |
100 | 0.914865 | 0.915434 | 0.056876 | 0.939760 | 0.937737 | 0.202300 |
Table 2.
Numerical results for comparison between the linear regression model based on the partial capacity of cell no.1 and a real SOH based on two partial capacities of cell nos. 2 and 3 (SOH error = Real SOH − Model SOH).
Table 2.
Numerical results for comparison between the linear regression model based on the partial capacity of cell no.1 and a real SOH based on two partial capacities of cell nos. 2 and 3 (SOH error = Real SOH − Model SOH).
Cell | Cell No. 2 SOH Information | Cell No. 3 SOH Information |
---|
Cycle | Real SOH | Model SOH | SOH Error (%) | Real SOH | Model SOH | SOH Error (%) |
---|
1 | 0.965090 | 0.963419 | 0.167070 | 0.990165 | 0.993270 | −0.310501 |
10 | 0.957525 | 0.955278 | 0.224684 | 0.981765 | 0.987842 | −0.607760 |
20 | 0.950520 | 0.947137 | 0.338295 | 0.975020 | 0.976987 | −0.196778 |
30 | 0.944530 | 0.938995 | 0.553407 | 0.969385 | 0.974274 | −0.488908 |
40 | 0.939880 | 0.936282 | 0.359777 | 0.964180 | 0.968846 | −0.466667 |
50 | 0.934080 | 0.925427 | 0.865259 | 0.959385 | 0.963419 | −0.403426 |
60 | 0.930230 | 0.925427 | 0.480259 | 0.955105 | 0.957991 | −0.288685 |
70 | 0.925500 | 0.920000 | 0.550000 | 0.950895 | 0.955278 | −0.438315 |
80 | 0.921900 | 0.917286 | 0.461370 | 0.947160 | 0.949850 | −0.269074 |
90 | 0.918015 | 0.917286 | 0.072870 | 0.943325 | 0.947137 | −0.381204 |
100 | 0.914865 | 0.914572 | 0.029240 | 0.939760 | 0.947137 | −0.737704 |
Table 3.
Numerical results for comparing between the linear regression model based on the IC curve peak point of cell no.1 and a real SOH for the IC curve peak point of the 12 series-connected stages of the retired series/parallel battery pack (SOH error = Real SOH − Model SOH).
Table 3.
Numerical results for comparing between the linear regression model based on the IC curve peak point of cell no.1 and a real SOH for the IC curve peak point of the 12 series-connected stages of the retired series/parallel battery pack (SOH error = Real SOH − Model SOH).
Number of Series Connected Stage | Real SOH | Model SOH | SOH Error (%) |
---|
1S | 0.923110 | 0.920901 | 0.220840 |
2S | 0.924775 | 0.920939 | 0.383523 |
3S | 0.889815 | 0.897681 | −0.786691 |
4S | 0.895785 | 0.899409 | −0.362452 |
5S | 0.916825 | 0.915565 | 0.125961 |
6S | 0.933365 | 0.929314 | 0.405027 |
8S | 0.938995 | 0.937269 | 0.172511 |
9S | 0.933220 | 0.924452 | 0.876734 |
10S | 0.962180 | 0.970388 | −0.820893 |
11S | 0.937520 | 0.930829 | 0.669058 |
12S | 0.951895 | 0.957149 | −0.525449 |
Table 4.
Numerical results for the comparison between the linear regression model based on the partial capacity of cell no. 1 and a real SOH based on the partial capacity of the 12 series-connected stages of the retired series/parallel battery pack (SOH error = Real SOH − Model SOH).
Table 4.
Numerical results for the comparison between the linear regression model based on the partial capacity of cell no. 1 and a real SOH based on the partial capacity of the 12 series-connected stages of the retired series/parallel battery pack (SOH error = Real SOH − Model SOH).
Number of Series Connected Stage | Real SOH | Model SOH | SOH Error (%) |
---|
1S | 0.92311 | 0.908345 | 1.476536 |
2S | 0.924775 | 0.911601 | 1.317391 |
3S | 0.889815 | 0.885278 | 0.453685 |
4S | 0.895785 | 0.890706 | 0.507944 |
5S | 0.916825 | 0.902374 | 1.445051 |
6S | 0.933365 | 0.915672 | 1.769336 |
8S | 0.938995 | 0.927612 | 1.138306 |
9S | 0.93322 | 0.911872 | 2.134754 |
10S | 0.96218 | 0.985414 | 2.323384 |
11S | 0.93752 | 0.927069 | 1.04508 |
12S | 0.951895 | 0.995183 | 4.328818 |
Table 5.
Numerical results for comparison between the linear regression model based on the IC curve peak point of cell no.1 and a real SOH for the IC curve peak point of a retired cell (SOH error = Real SOH − Model SOH).
Table 5.
Numerical results for comparison between the linear regression model based on the IC curve peak point of cell no.1 and a real SOH for the IC curve peak point of a retired cell (SOH error = Real SOH − Model SOH).
Cycle | Real SOH | Model SOH | SOH Error (%) |
---|
1 | 0.986639 | 0.986639 | 0.867415 |
30 | 0.975 | 0.975 | 0.576596 |
60 | 0.96305 | 0.96305 | 0.007766 |
90 | 0.94125 | 0.94125 | 0.753881 |
120 | 0.931 | 0.931 | 0.226191 |
150 | 0.91265 | 0.91265 | 0.264107 |
180 | 0.89699 | 0.89699 | 1.303744 |
210 | 0.893 | 0.893 | 0.849753 |
240 | 0.891 | 0.891 | 0.458948 |
270 | 0.87475 | 0.87475 | 0.268324 |
300 | 0.868756 | 0.868756 | 0.31217 |
330 | 0.84825 | 0.84825 | 0.66615 |
360 | 0.8582 | 0.8582 | 0.968274 |
390 | 0.823913 | 0.823913 | 0.103044 |
420 | 0.82225 | 0.82225 | 0.130594 |
450 | 0.817438 | 0.817438 | 0.631443 |
480 | 0.81 | 0.81 | 0.633386 |
510 | 0.8 | 0.8 | 0.585745 |
540 | 0.78495 | 0.78495 | 0.333081 |
570 | 0.7795 | 0.7795 | 0.01941 |
600 | 0.770695 | 0.770695 | 0.469788 |
Table 6.
Numerical results for the comparison between the linear regression model based on the IC curve peak point of cell no. 1 and a real SOH for the IC curve peak point of the retired cell (SOH error = Real SOH − Model SOH).
Table 6.
Numerical results for the comparison between the linear regression model based on the IC curve peak point of cell no. 1 and a real SOH for the IC curve peak point of the retired cell (SOH error = Real SOH − Model SOH).
Cycle | Real SOH | Model SOH | SOH Error (%) |
---|
1 | 0.986639 | 0.992469 | 0.583047 |
30 | 0.975 | 0.983826 | 0.882632 |
60 | 0.96305 | 0.969539 | 0.648867 |
90 | 0.94125 | 0.94168 | 0.042978 |
120 | 0.931 | 0.936639 | 0.563908 |
150 | 0.91265 | 0.929484 | 1.68344 |
180 | 0.89699 | 0.912421 | 1.543112 |
210 | 0.893 | 0.917028 | 2.402849 |
240 | 0.891 | 0.935129 | 4.41289 |
270 | 0.87475 | 0.89749 | 2.273982 |
300 | 0.868756 | 0.895265 | 2.650909 |
330 | 0.84825 | 0.8773 | 2.904986 |
360 | 0.8582 | 0.876811 | 1.86114 |
390 | 0.823913 | 0.860163 | 3.625032 |
420 | 0.82225 | 0.851085 | 2.883548 |
450 | 0.817438 | 0.846608 | 2.917037 |
480 | 0.81 | 0.831167 | 2.116689 |
510 | 0.8 | 0.812551 | 1.255088 |
540 | 0.78495 | 0.8081 | 2.315041 |
570 | 0.7795 | 0.80483 | 2.533039 |
600 | 0.770695 | 0.793012 | 2.231771 |