GID loss & Turtle mode question...

[philipscoggins]

In May of this year I finally got around to range testing my 2012 LEAF. I started with a reading of 270 GIDs & ended with 4 GIDs (btw, 130.3 miles).

So, my problem is that after running my LEAF down to dead, my battery quickly dropped to a full charge of around 255 GIDs & now I'm down to 245-250 GID on a full charge. It seems directly related to running my battery all the way down (yes I did plug it in immediately and charged for an hour or so, to keep it from sitting at empty)

I searched, but couldn't find a GID number where I can expect my first capacity bar loss, but expect it to be coming up. I'm a little over 20,000 miles and right at 10 months ownership.

Have you guys (and gals) experienced a rapid GID loss after running the battery dead? If so, shouldn't we warn people not to do it unless absolutely necessary, as in, don't range test to the point the battery is dead?

If this has already been covered, please point me to the topic & I'll delete this one.

Philip

 

[RegGuheert]

Have you guys (and gals) experienced a rapid GID loss after running the battery dead?

Yours is the first report I recall of such a precipitous loss following a single range test. We do have the history of Tony's LEAF losing about 13% capacity in a year or so after MANY, MANY trips to dead. I always figured the real issue there was the 23,000(?) miles he had on the car.

If so, shouldn't we warn people not to do it unless absolutely necessary, as in, don't range test to the point the battery is dead?

I think that is good advice in any case. There is a reason that GM does not let the Volt battery get below 20% SOC.

In your case, the big drop could simply have been due to the BMS finally getting a good reading on all of the cells over their entire range. While I have always optimistically imagined GAINING capacity after such a calibration, it makes sense that you could just as easily lose capacity that the BMS thought was there but really wasn't.

Your post is very timely for me, as I have three fairly long LEAF excursions upcoming this month and I have been debating whether or not to discharge it to a very low value or not.

 

[philipscoggins]

I drove alot (single dad 3 kids, lots of trips). I regularly get home on LBW, but only about once a month on VLBW. I'm averaging 90 miles on my odometer every day now that the kids are back in school.


Philip

 

[johnrhansen]

I try to never get the charge below 20 percent. The best thing a guy could do in my opinion is get a full size EVSE so you can charge at maximum capacity in the middle of that day when you are at home, even for a half hour. I kept my ice truck. Sometimes during a hectic day I will take my truck on a short errand while my electric car charges... this way no sweating range and no blinking low charge indicator lights!

 

[philipscoggins]

I usually charge at lunch & if I have errands to run I have permission to plug in (110) at work.

Philip

 

[TickTock]

I think it is just coincidence. April-June is where we see a lot of seasonal drop in gids. You should start to see your gid count rise soon (although it will not get back to where is was). Take a look at the graph I posted here. You can see that, starting April, gid count (blue dots) drops precipitously but recovers starting in October. During all this time the true capacity (other colored dots) degrades much more steadily. This seasonal variation, I think, contributed a lot to the hysteria last year as it makes it appear that the battery is degrading faster than it really is.

 

[philipscoggins]

Thanks ticktock, this was my first summer in the LEAF. I didn't realize GIDs come back with cooler weather. I've been getting lower 5s in m/kW, so I can get 90 miles in most days & was worried it was going to keep dropping at the same rate.

Philip

 

[surfingslovak]

I think it is just coincidence.

Same here. Please keep in mind that these cells are typically tested over a much wider range of voltages in the lab. Typically from 2.5V to 4.2V (the maximum voltage should be a bit lower for LMO cells). Turtle cutoff on the LEAF is in my experience about 3.2V, but lower values have been reported also. The rated capacity the manufacturer is using is presumably also based on a similar wide range of voltages. While it's not advisable to deep cycle the battery on a daily basis, because shallow cycling should be beneficial for the longevity of the pack, an occasional trip to turtle should not have a large and noticeable ill effect on the battery. That said, it's advisable to drive gently as you approach lower SOC reaches, if you can. I think the rationalization about the BMS learning the full potential of the battery through a deep cycle or two is more likely, as is the timing of the arrival of warmer weather. When my LEAF's battery dropped from 281 to 270 and then 265 in a matter of 2 or 3 months, I thought it was because my friend let it sit an entire weekend fully charged. In reality it was most likely the result of of the second spring and summer.

 

[philipscoggins]

Thanks for the uplifting information! I'll try to relax some. Summer in TN was hot at the beginning, not too bad in the middle & now back up in the 90s at the end. Hopefully I'll see some come back.

Philip