Video of behavior where rapid discharge becomes apparent at 40s:
Rapid (reported) battery disharge in low-ish temps and moderate-high power output
My 2013 Leaf @ 57k miles experiences rapid (reported) battery discharge followed by a "limited motor power" warning and sporadic drivetrain power output (which can be scary). This happens when requesting more than 40% power for more than 10-20s, in ambient temperatures of around 30°F or less. Once power is no longer requested (i.e. you stop the car), the reported remaining charge will slowly climb back to where it might
have been had the rapid discharge event not taken place. This can be seen towards the end of the video.
I've taken my car to a dealer, and they said this was caused by "normal battery capacity degradation", but I disagree. The battery capacity has certainly lowered, but a lower capacity equates (in my mind) to "less range per full charge", which is very different from "99% less range when it's kind of cold, and normal range when it's slightly warmer." I'm reaching out to you all to help diagnose the issue.
The discharge rate can be as high as 2 to 3 percent PER SECOND if more than 80% power is requested. In the video I'm requesting 50% power and it drops from 50% to 36% in 17 seconds (0.82%/s). If the ambient temperature is above 40°F this does not happen at all; no significant increase in discharge rate, and no "limited motor power". For comparison, see https://www.geotab.com/blog/ev-range/
, where I should (according to their plot based on a broad range of BEVs and over 4 million trips) expect a range decrease of around 10% due to a decrease from 40°F to 30°F (very similar to the data for only Nissan Leafs here: https://www.greencarreports.com/news/10 ... n-the-cold
). Also see https://avt.inl.gov/sites/default/files ... ne2016.pdf
, a study based entirely on 2015 Nissan Leafs, where the range decreased from ~75mi to ~65mi (figure 5 on page 7) due to the same decrease in temperature. What I'm seeing is a temperature regime where my range drops from 50 or more miles to essentially 1 or 2 miles.
As you can see, my battery is at 7 "bars", so it's not a spring chicken, but I still get 50/65 miles of range in the winter/summer, which is proportionate to what you would expect based on its initial range and its reported health. Under the rapid discharge conditions shown in the video, however, the car will drop from 75% to 0% in less than two minutes.
I see this as a "failure", in that the car is nonfunctional (and dangerous, as the sporadic power output tosses the car back and forth). Further, the fact that the behavior is completely different at 30°F than at 40°F, it seems like there is something failing that causes this behavior.
To me, this looks like a voltage issue. As I mentioned above, after you stop the car, the reported remaining charge will slowly climb back to where it might
have been had the rapid discharge event not taken place. So the charge isn't "going" anywhere; the car is erroneously reporting a lower remaining charge than what is actually in the battery.
Remaining charge is estimated using the output voltage of the battery, so for the car to report a lower remaning charge means that it thinks
that the voltage from the battery is dropping dramatically. This could be one or both of two things:
1. The voltage from the battery is actually dropping FAR BEYOND even the worst expected case for battery voltage as a function of temperature, or
2. There is a sensor (perhaps a voltmeter, or a thing the voltmeter is connected to) somewhere that is, under the conditions of cold-ish and a moderate-high load, failing and providing erroneous voltage readings, causing the remaining charge estimate to lower.
I'm ambivalent to which one it is. I just want my car to not suddenly die and swerve off the road every time I go uphill in barely freezing temperatures. A new battery would be nice but unnecessary as the Leaf's current range is sufficient.
Insufficient battery voltage
The technician has already looked over the battery, and says he's confirmed that there are no leaking cells, and the car isn't reporting any diagnostic codes related to battery failure. That being the case, if it is actually the voltage from the battery that's dropping, then I'm at a loss for what the underlying cause might be given that it's not obvious to the techs.
Since this is a problem causeed by low temperature I thought about the battery heating/cooling. I know that the battery "warmer" doesn't come on until the battery temperature drops to -1°F, and then it turns off once the battery temperature has climbed back up to 14°F, and only if the reported remaining charge is > 30% (page EV-5 of owners manual https://owners.nissanusa.com/content/te ... manual.pdf
). That doesn't seem to apply here, hence I can't think of what it might be.
If the problem is a sensor or some intermediate chip between the sensor and the car computer, then I guess they could test it (in a freezer?) with a known voltage and isolate the problem.
That's all I have on it. I've ordered an ODB sensor and I'll dig in with Leaf Spy Pro to identify the bad cell(s), if that's the problem, by observing individual cell voltages when driving and when charging.
Beyond that, thanks in advance for any help approaching the issue, or tips for what the technicians might do to diagnose the problem.