JPVLeaf said:
surfingslovak said:
JPVLeaf said:
To add to the data pool, I took my Gid-meter this past week to three other Leafs after completing a '100%' charge and got the following:
1. 7.5 mos, 8600 mi., 269 Gids (95.7%), 5x charges/wk from 60% to 100% overnight, Orange Cty.
2. 7 mos, 7500 mi., 269 (95.7%), 4-5x charges/week from ~25% to 100% thru mid-day, San Bern Cty (inland So Cal).
3. 10.5 mos, 10000 mi., 265 (94.3%), 4-5x charges/week from ~40% to 100% thru mid-day, San Bern Cty (inland So Cal).
My charging pattern is closer to #2. Considering my higher mileage, I'm not feeling too bad about my recent 260-265's. But, if a later dip into the 250's doesn't correspond to a rise in the day's temp, ....
Thank you, Richard! JP, any additional details you could share?
1. silver, never turtled, only charges/rides in central/south OC, #90xx
2. black, turtled/died once, mainly inland, SB Cty, #39xx
3. black, never turtled, mainly inland, SB Cty, #11xx
As most here know, it's not really appropriate to conclude a remaining battery capacity based on single readings, as for the above three Leafs. For example, Leaf no. 1 above, has since reached 272. At a minimum, you'll need a history of readings to 100%. Conclusions about battery capacity losses should probably be based on no less than the recent highest readings. For example, based on the recent 272, I'd say that no. 1 has more likely lost no more than 3%. And even then, there's still some uncertainty related to that's battery pack's cell balancing status ....
My data:
I used cool recent weather (65 deg F evening, 62 deg F overnight low), to do a rare test of my 100% charge. Result:
271 gids, or 3.6% loss.
I repeated second night, same result.
My 80% charge point has declined from 82.2% to 80.0%/
11,000 miles, 11.5 months, lowest two SOC events were 7.5% and 12.5%. 5-6 QCs, only one more than 50%. #2500.
Last few months, estimate:
30% nights no charge,
35% nights 80% charge
30% nights 90% charge
5% nights 100% charge
I believe this early capacity loss most of us have observed is some mixture of unavoidable "shelf-life" loss and usage-dependent loss. I don't know what the mixture is, but I am going to get more aggressive in my own effort to minimize the rate of additional loss, because loss of 10% or more in range is going to impact frequent trips that have not needed in-route charge up to now.
My new goals for charging:
30% nights no charge
25% nights charge to 70-75%
35% nights charge to 80%
8% nights charge to 88%
2% nights charge to 92%
When I first finished my SOC meter in late Aug 2011, I never saw more than 274 gids, but with the onset of cooler Fall weather the readings went up, and I hit 281 for most of my winter once-per-month 100% checks. Last 281 was probably February.
Of course we all hope that perhaps the 100% charge has stopped somewhat early because our cells are not perfectly balanced.
Here is my model:
When charging to 100%, the BMS stops the charge when the battery cells reach a pre-determined fixed voltage selected by Nissan, apparently about 95% of the maximum safe voltage. If the 96 cell-pairs are not perfectly balanced, the first pair to reach this voltage stops the charge, leaving other cells at lower voltage.
As the battery's capacity declines, the cells reach the same maximum voltage early, with fewer coulombs of charge, and therefore fewer gids. The bars, the 80% threshold, and the 100% threshold are all tied to fixed voltages, so the pack reaches these points with fewer gids. There is no reason this effect has to be linear, so it is quite possible that there is more loss of gids in the upper bars than the lower bars.
I believe we can check for the unbalanced condition by monitoring the total pack voltage at the 100% charge condition. According to my model, if the pack is balanced at 100% charge, all the cell-pairs will have the maximum allowed voltage, and the total pack voltage displayed by the SOC meter will also be at a fixed maximum that should be the same for everyone. Conversely, the pack will be out-of-balance if and only if the pack total voltage is less than this maximum, because some of the cell-pairs are not at their maximum values.
At my 100% test, the pack voltage was either 394.0V or 394.5V.
My 80% charge point is 387.5V. I would be interested in how these values compare to other folks' voltages.
