Marathon pack analysis... complete!
I literally just finished. See for yourself:
Google Docs spreadsheet of MetroMPG's pack analysis
And here's the summary:
- 6 of 20 sticks showed a discharge capacity below 5500 mAh (I'm told this is the capacity below which you should consider replacing them)
- 4873 mAh - the lowest discharge capacity found. This stick effectively limits the entire pack to this capacity, which is 75% of nominal.
- Waaay out of balance -the initial discharge revealed the pack was a mess, in terms of how close the sticks were to one another in state of charge (SOC).
10 of the sticks were effectively "empty" (0% SOC); while one was as high as 43% SOC!
As IamIan mentioned, it appears this was actually the biggest issue affecting the pack, rather than individual stick capacity loss (though they obviously both contribute).
- Unusually high self-discharge in one stick? I'm not 100% certain whether this was a mistake in my testing, but stick #15 showed very high self-discharge after 7 days relative to the other sticks. I retested it again after 3 days, and it was more in line with what I would expect to see, but to be safe, I think I'll retest it again after 7 more days.
Next steps:
My grid charger should arrive in the next week or so. I need to hook it up to the pack, reassemble everything, and put it in the car.
I'll make sure the pack is fully balanced before putting it back in the car.
Then I'll take it for a drive & see how it performs.
I haven't ruled out replacing some of the lower capacity sticks, but want to try it in its newly balanced state first.