Bottom Misbalancing Act III

Quest for an Electric Porsche Boxster.

I bottom balanced again, this time down to 2.5v +/- 0.05v with shunt balancers. About 68Ah went into pack before blade 42-1 became full which I carefully allowed up to 3.8v at 1A on charger. The closest next cell was at 3.3v. Following is at the end of test drive conservatively averaging about 65mph, mostly freeway:

01 2866 037 2869 037 2862 037 2862 037
02 2860 038 2882 038 2855 038 2852 038
03 2705 041 2584 041 2688 041 2505 041
04 2697 045 2732 045 2694 045 2519 045
05 2677 047 2653 047 2714 047 2694 047
06 2913 043 2931 043 2926 043 2865 043
07 2463 046 2628 046 2633 046 2623 046
08 2635 044 2613 044 2634 044 2685 044
09 2615 042 2635 042 2664 042 2567 042
10 2739 050 2734 050 2648 050 2669 050
11 2710 048 2737 048 2699 048 2691 048
12 2641 048 2684 048 2678 048 2699 048
13 2739 048 2730 048 2724 048 2616 048
14 2672 047 2699 047 2672 047 2687 047
15 2723 047 2707 047 2665 047 2672 047
16 2656 045 2657 045 2648 045 2630 045
17 2606 044 2623 044 2649 044 2639 044
18 2657 051 2650 051 2642 051 2623 051
19 2852 044 2863 044 2849 044 2847 044
20 2646 047 2649 047 2667 047 2695 047
21 2862 044 2884 044 2878 044 2824 044
22 2851 044 2866 044 2857 044 2860 044
23 2634 051 2669 051 2667 051 2646 051
24 2836 043 2864 043 2814 043 2802 043
25 2663 047 2662 047 2703 047 2686 047
26 2619 049 2643 049 2590 049 2646 049
27 2656 053 2635 053 2698 053 2628 053
28 2667 053 2634 053 2688 053 2695 053
29 2577 051 2540 051 2543 051 2600 051
30 2593 049 2647 049 2671 049 2664 049
31 2651 051 2554 051 2657 051 2667 051
32 2636 042 2598 042 2623 042 2588 042
33 2640 044 2675 044 2713 044 2700 044
34 2663 049 2702 049 2684 049 2686 049
35 2660 051 2502 051 2618 051 2676 051
36 2571 053 2583 053 2647 053 2628 053
37 2615 049 2657 049 2656 049 2669 049
38 2876 047 2882 047 2894 047 2893 047
39 2595 049 2578 049 2612 049 2588 049
40 2917 048 2927 048 2923 048 2899 048
41 2616 049 2663 049 2672 049 2695 049
42 2506 051 2706 051 2740 051 2745 051
43 2573 051 2566 051 2613 051 2597 051
44 2672 049 2661 049 2663 049 2681 049
45 2874 046 2881 046 2908 046 2882 046
46 2664 048 2653 048 2705 048 2700 048
47 2625 048 2617 048 2599 048 2640 048
48 2644 041 2639 041 2667 041 2667 041

Max Voltage: 2931 (62)
Min Voltage: 2463 {71)
Max Temp: 53
Min Temp: 37
under load coming into driveway
66.4Ah 41.3m, 1.6 Ah/mile

after 5min, increased to 2.8v drove around block again:

01 2912 038 2917 038 2914 038 2910 038
02 2897 041 2906 041 2910 041 2912 041
03 2778 042 2754 042 2778 042 2731 042
04 2801 047 2811 047 2796 047 2750 047
05 2759 050 2761 050 2787 050 2783 050
06 2921 044 2930 044 2932 044 2910 044
07 2745 047 2762 047 2774 047 2773 047
08 2761 045 2750 045 2767 045 2787 045
09 2743 044 2750 044 2766 044 2726 044
10 2802 052 2804 052 2770 052 2786 052
11 2790 049 2803 049 2787 049 2784 049
12 2764 050 2783 050 2779 050 2787 050
13 2800 050 2794 050 2795 050 2758 050
14 2773 049 2787 049 2770 049 2770 049
15 2791 049 2789 049 2758 049 2774 049
16 2757 047 2757 047 2764 047 2756 047
17 2744 044 2760 044 2768 044 2762 044
18 2782 052 2777 052 2773 052 2777 052
19 2906 046 2908 046 2906 046 2904 046
20 2749 048 2754 048 2748 048 2756 048
21 2906 046 2910 046 2912 046 2905 046
22 2903 045 2914 045 2909 045 2908 045
23 2753 052 2771 052 2767 052 2765 052
24 2908 044 2912 044 2907 044 2894 044
25 2765 049 2759 049 2760 049 2759 049
26 2750 050 2748 050 2714 050 2748 050
27 2767 054 2750 054 2769 054 2746 054
28 2770 055 2746 055 2763 055 2761 055
29 2737 053 2711 053 2708 053 2735 053
30 2746 051 2775 051 2763 051 2774 051
31 2760 051 2756 051 2752 051 2761 051
32 2755 045 2764 045 2742 045 2744 045
33 2760 045 2773 045 2784 045 2774 045
34 2790 050 2799 050 2783 050 2788 050
35 2796 052 2579 052 2783 052 2790 052
36 2736 055 2735 055 2751 055 2740 055
37 2761 050 2780 050 2767 050 2787 050
38 2924 049 2921 049 2925 049 2924 049
39 2755 050 2742 050 2753 050 2727 050
40 2920 049 2925 049 2918 049 2909 049
41 2762 051 2778 051 2764 051 2774 051
42 2671 053 2784 053 2790 053 2794 053
43 2738 053 2738 053 2739 053 2740 053
44 2753 050 2733 050 2736 050 2757 050
45 2924 048 2929 048 2926 048 2920 048
46 2774 049 2771 049 2785 049 2785 049
47 2757 049 2752 049 2734 049 2755 049
48 2780 040 2792 040 2787 040 2788 040
Max Voltage: 2932 (63)
Min Voltage: 2579 {352)
Max Temp: 55
Min Temp: 38
68.2Ah, 42m, 1.62Ah/mile

I squeezed out another 3Ah on the last test drive, but went a bit lower on average end of discharge voltages. The overdischarge two weeks ago cost me 6-7Ah total capacity and about 4 miles range compared to best range test before overdischarge. I believe the loss is mainly from 42-1 which was low to begin with. I don't think blades 5 or 27 are seriously damaged. But they are lower than the average blade in the pack which is about 15% less than it should be after accounting for perhaps 4% per year loss in storage with K2 cells. I am not sure other LiFePo4 cells have the same problem as most are not documenting it.

I don't think bottom balancing will work with this many cells and without similar capacity cells, so I am going back to top balancing for now. I will recheck conservative range after top balancing, and I think it is about the same since I was getting about 65Ah capacity after the overdischarge event.