Sucking Them Dry

At the moment I’m in the final stages of “bottom balancing” the pack. I’ve sucked every single cell way below 3 volts with my Graupner Ultramat 16S computerized charger and now I’ve begun the second pass, as the voltages have bounced up again as expected. But this time the time required to drop the voltages (again) is much lower than the first pass and the amp hours remaining that are drained, are very minimal. The cells are nearing empty. So it’s only the fine tuning left. The charger I’ve set to discharge with 5A current, and all the cells had pretty even 20Ah of juice in them before I started. So it took about 4 hours per cell to discharge them below targeted value. But once the charger stops, they bounce up again within next day, as “lithium ions find their places”. So I need to repeat this until all cells read pretty much the same, 2.75 volts.

So far, looking good…

Bottom Balancing


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