New England Hybrid Festival 2013
Mikes You Tube Videos
Mikes Saturday Hybrid-Solar- Electric Workshop
Insight 20 AH lithium battery system
Grid charger Users page
Mikes Surplus Loft
Renewable energy exhibits

Early results of subpack testing

Early results of subpack testing
Ian's test setup

Ian has ran each subpack through at least one cycle of charge/discharge to determine AH, effect of cycling, and potential cell imbalances.
Here is the firs look at the data.

#1> Determine the Capacity of the sub-packs
#2> Determine effect of cycling sub-packs
#3> Compare cell resistances in sub-packs

Cell resistance variation can be seen in the difference in temperatures.
Must make sure to take into account the how batteries charge as a sub-pack.
Each cells resistance is in series
Cells in series all have the same current but not the same voltage.
The heat / resistance can also be cause by cells that are lower capacity reaching full capacity sooner.
Once a NiMH battery reaches its SOC Capacity any further charging will see a temperature increase.
This is a variable resistance based on battery SOC.
Faster / higher current charges and discharges will more show the resistance of the battery / sub-packs
Slower / lower current charges and discharges will more show the true capacity of the battery and more fully cycle it.

4 subpacks started with 0000 mAh of initial SOC
6 subpacks started with over 2,000 mAh of initial SOC

9 subpacks initially took ~6,000+ mAh of charge
4 subpacks initially took less than 3,000 mAh of charge

Fast / High Current Cycles
Discharge at 3.0 Amps Charge at 5.0 Amps
Set for NiMH 6 cell pack 6,000 mah expected 7,000 mah limit
Discharge to 0.9 V per cell x 6 cells = 5.4 V per Sub Pack
There is a 15 minute delay between discharge and charge
* = Ian Aborted charge due to temp reading

Slow / low current Cycles
Discharge at 1.0 Amps Charge at 1.0 Amps
Set for NiMH 6 cell pack 6,000 mah expected 7,000 mah limit
Discharge to 0.9 V per cell x 6 cells = 5.4 V per Sub Pack
There is a 15 minute delay between discharge and charge
Slow / low current does not seem to be producing temp variation in cells of sub-pack

Subpack Cycle Date Action Vi mAh Degrees F + Left to - Right

#1 1Fast 8/4 Disch 8.2 959 89
Charge 3278 88 95 92 98 100 102

#2 1 Fast 8/4 Disch 6.7 125 86
Charge 2840 88 91 99 101 93 99

#3 1 Fast 8/4 Disch 7.59 2439 85
Charge 6739* 118 117 114 114 113 115

#4 1 Fast 8/6 Disch 6.68 0000 80
Charge 3977 92 95 100 101 91 93

#5 1 Fast 8/6 Disch 5.89 0000 80
Charge 3111 89 98 100 92 99 90

#6 1 Fast 8/6 Disch 6.93 140 80
Charge 2920 89 90 95 91 99 98

#7 1 Fast 8/6 Disch 6.99 137 79
Charge 3432 91 99 102 100 96 91

#8 1 Fast 8/6 Disch 6.95 173 80
Charge 2794 98 91 94 101 92 102

#9 1 Fast 8/7 Disch 7.58 2360 83
Charge 6009 97 100 100 98 97 97

#10 1 Fast 8/7 Disch 7.57 2228 85
Charge 5954 100 107 109 103 98 103

#11 1 Fast 8/8 Disch 7.2 37 83
Charge 2872 90 95 102 100 95 96

#12 1 Fast 8/8 Disch 6.96 195 85
Charge 3466 97 95 93 97 102 104

#13 1 Fast 8/8 Disch 5.84 0000 85
Charge 3424 106 99 94 92 92 95
2 Slow 8/10 Disch 8.18 2614 73
Charge 7000 80

#14 1 Fast 8/9 Disch 7.27 1300 79
Charge 7000 109 112 119 121 111 114

#15 1 Fast 8/9 Disch 6.4 1358 87
Charge 7000 112 110 114 117 106 118

#16 1 Fast 8/10 Disch 7.3 1775 66
Charge 6493 89 98 96 97 96 98

#17 1 Fast 8/6 Disch 7.63 2658 80
Charge 6139 109 112 113 110 111 103

#18 1 Fast 8/5 Disch 7.04 2309 83
Charge 6159 91 103 103 100 102 98
2 Slow 8/8 Disch 8.03 5163 78
Charge 7000 83

#19 1 Fast 8/5 Disch 5.82 0000 80
Charge 4026 90 91 93 98 101 101
2 Slow 8/9 Disch 7.8 3059 79
Charge 6751 81

#20 1 Fast 8/5 Disch 7.59 2646 76
Charge 6743 106 110 102 111 113 110
2 Slow 8/8 Disch 8.0 5479 80
Charge 6851 82

Obviously the pack was badly unbalanced.
The interesting thing here was that the pack was working relatively normally and had no IMA code in the silver Insight that it came from.I did have problems trying to start the car after it sat for some time.
Ian Cycled each subpack and found that they all seemed to respond with nearly full AH in subsequent cycles.