Wildly inaccurate battery %

My 2019 Leaf plus battery percentage decreases normally to about 70% then begins to plummet. On my most recent drive, I started at 86% and after driving 56 miles was indicating 22% remaining. Leaf Pro said I had 63% remaining, and I used that figure to calculate time needed to bring the battery to 85%. The charge indicator worked normally for the first year, but began giving me bogus information a couple of months ago. Has anyone else encountered this problem?

One bit of information I forgot to include in my post is that Leaf Spy indicates that cell #68 is weak. Could one weak cell cause this problem?

The Distance To Empty (DTE or GOM, aka Guess-O-Meter) has always been optimistic on my 2019 SL Plus. It tends to drop faster after the battery is partially discharged (the SOC % display also drops faster as the DTE drops). I have a couple of cells that Leaf Spy sometimes shows as weak, but am not too worried about them. If you have a failing cell that just started showing as weak, it may be causing the change you are seeing.

It could help to run the car down to 0% indicated SOC and then take a reading with LeafSpy. It would be interesting to see what the low cell is reading at that point. I'd do this close to home in case the car decides to go into turtle mode at some point.

WLJ said:

One bit of information I forgot to include in my post is that Leaf Spy indicates that cell #68 is weak. Could one weak cell cause this problem?

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Yes.

There is another recent thread almost identical to yours.

Yes. I am fairly sure the battery % becomes correlated with the lowest cell voltage when the lowest cell is below a certain voltage . I know that sounds confusing. Above that voltage, it looks like it sets 100% by multiplying pack ahr times pack voltage, and then reduces battery % based on ahr discharged. Battery % drops slowly, GOM is dropping slowly as well--pack looks normal. Then the lowest cell crosses some voltage, and the battery% is now based on tracking the weakest cell (and likely using some calibration curve in the firmware). Battery % plummets, GOM does as well. You may notice that after really dropping quickly, it slows down again.

I could be totally wrong.

MikeinPA said:

I could be totally wrong.

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Sounds right to me

Update 1. Was on my way to dealer to check weak cell when EV warning light illuminated 5 miles from dealer and car went into turtle mode. Left car at dealer where I was told battery will be pulled and faulty cell replaced or entire battery will be replaced under warranty.

Update 2. Good news: Bad battery module will be replaced under warranty. Bad news: Module will be shipped from mainland to Hawaii by boat, which will take about 3 weeks.

^^^
That is good news they determined what's wrong. Did they give you a loaner? That's a hell of a long wait.

They did give me a loaner,but it wasn't made clear at the time that it was a loaner. I thought I had rented a car until I returned it 2 days later, and was told that Nissan would have covered the cost. Fortunately we have a spare car, and I only needed the loaner to drive 50 miles home since no one was available to pick me up at the time. One problem with living in Hawaii is that retailers like Amazon will not ship anything with a lithium ion battery to Hawaii, and anything with a L-I battery that is shipped must come by boat, which takes a minimum of 2-3 weeks.

The dealer provided a loaner, and the battery module arrived in 3 weeks, but another part was required, so after 5 weeks my car was returned as good as new.

Great news...enjoy that car now