So I guess in a way the change was immediate but there were too many variables to really tell. That replacement cell for the one I punctured? It was super out of whack with all the other cells. Using leaf spy, it hit as much as 120mv of difference between the others. This could have limited the charging of the other cells, preventing us from getting more range. Perhaps it just took 9 months for the battery to balance.
It has been a while since I've looked at leaf spy but I can check it out and see if the battery has balanced. I don't have the car right now but I'll check on it when I do. Are there any other stats you want me to look at while I'm at it?
The reason I asked is the GOM doesn't change as the result of a cell swap, at least not right away. The dealership has to reset the BMS during a cell swap to reset the GOM, which you didn't do. But even though the GOM doesn't change, the pack should drain much slower on account of the better cells. So you might swap packs and see "30" on the GOM... but then drive the car 60 miles. So you can't rely on GOM and gids and such until the BMS has had a chance to re-learn... only driving the car will really tell you the situation.
IFIRC, the Leaf balances batteries by putting a shunt resistor between cells during charging and discharging, which can accommodate small differences in cell capacity within a pack. However, if the cell difference gets too large, then you see something like this:
https://www.dropbox.com/s/tre68n125b99a57/2014-08-16-13-32-20.jpg
(from http://www.mynissanleaf.com/viewtopic.php?f=27&t=7022&start=760#p383786 )
Here's a discussion about imbalanced cells
http://www.mynissanleaf.com/viewtopic.php?f=9&t=17676&start=10
If the replacement cell you got was stronger than the rest of your cells by a large amount, no biggie. You're just wasting some capacity on that cell. But if that cell is weaker than the rest of your pack, you're wasting the remaining capacity of the entire pack when the one cell hits low voltage cutoff, which could be a ton of energy (miles).
Keep in mind that the initial charge (voltage) of that cell isn't critical. The BMS will eventually, over a few charge-discharge cycles be able to balance it back into line during charging using the shunt resistors. Ideally, you should have stuck that one cell on a lipo charger and charged it to the same voltage of the rest of the pack, but the BMS has resolved that now.
What really does matter is if that cell's capacity is significantly less than the rest. If so, it will be artificially limiting your range because once that cell falls below the low voltage cutoff, the entire car will shut down. You should see that in the LeafSpy--measure the difference in mv in all the cells at full charge, drive to near turtle (-- to 2 miles on GOM) and then recheck individual cell voltages with LeafSpy. If you see one cell that's significantly lower than the rest, this is significantly hurting your range. Replacing just that one cell with a better cell could significantly increase your range.
In fact, I suspect this is where Nissan gets a lot of the refurbished packs from for Japan--it's well documented that the center cells in the pack heat up more and thus deteriorate faster than the outside cells. By just replacing the center cells you can dramatically increase the pack capacity. Since Nissan has gotten a lot of batteries back during pack swaps, they likely have a lot of good cells (and a lot of bad ones too).
Sent you a DM with my phone # if you want to talk more.