RegGuheert on December 14, 2017 wrote:Capacity degradation on our LEAF is now accelerating, with 2.6 Ah lost between 40,000 and 50,000 miles while we only lost 2.2 Ah between 30,000 and 40.000 miles. That is true even though the vehicle was driven those last 10,000 miles over a shorter period of time, so calendar losses during that last period should have been a bit lower.
So now I'm not so sure. As I reported previously, our LEAF has been showing increasing Ah readings recently
. Since crossing 50,000 miles on December 7, 2017, at 47.21 Ah, the reported capacity has increased to 48.24 Ah on Februrary 11, 2018, with about 52,000 miles on the odometer.
So, has capacity loss accelerated from 2.2 Ah/10,000 miles (30,000 mi. to 40,000 mi.) to 2.6 Ah/10,000 miles (40,000 mi. to 50,000 mi.) or has it slowed to 1.6 Ah/12,000 miles (40,000 mi. to 52,000 mi.) or both?
Beats me, but I have a new theory about why the capacity has been increasing as of late. I think the BMS may be responding to our efforts to charge the battery to higher SOCs this winter by pressing the timer override button one or more times after the battery has completed its normal charge cycle. We started doing this because the combination of battery degradation (with the associated loss/reduction of regen), new tires and colder temperatures have made my wife's 50-mile commuted quite marginal this winter, even at temperatures of 20 degrees or more. Pressing the timer override button really DOES add more charge to the battery and I think the BMS interprets that as the battery having more capacity.
If that theory is correct, then I suppose when Spring comes around, we will get rapid reported
capacity loss due to three different effects: 1) Loss of capacity due to no longer pressing the timer override button, 2) Loss of reported
capacity as it warms up (It does that every year!), and 3) Loss of capacity that has been going on all along that has been masked by pressing the button.
We'll see. Perhaps the capacity loss reported over the 50,000- to 60,000-mile interval will shed some light on what is actually happening.