Enveiling the i-MiEV battery degradation mystery

[Malm]

Here in Portugal Nissan Leaf owners, with 2 and an half years and 35.000 miles, all have 18 to 25% degradation. That's strange for me that we all are far from that. Even me, I couldn't ride that 200 km last summer if I have such degradation. So, I´m suspecious, but far from certain, that an i-MiEV, when it is new, only charge 16 kW.h, when it's batteries could charge more, maybe 16,5 kW.h. An i-MiEV is prepared to charge 16 kW.h, never more (even if it could). When degradation advances, and batteries only can take 16 kW.h (lost 0,5 kW.h of original capacity), they will charge the same 16 kW.h, and so we will ride the same distance as it was new. When it is 1 year old, it could have 3% degradation but exactly the same autonomy.

This method of "hiding" degradation is used on motorbikes like Vectrix, but never described for the i-MiEV (I think), so just an idea.

Now that I have more then 3% degradation, I see one bar going away when I stop for awhile. Charges 16 but when I stop after 20 miles, when I start it, one bar is not there any more. That's it telling me that 5% of energy in not there anymore. So 3% + 5% of degradation after 3 years. Even so, much better then the Leafs.

 

[PV1]

I've always thought hiding capacity was a good long-term idea. This way you maintain the same range for much longer before degradation shows.

I've also heard that the i-MiEV battery is a different chemistry than the LEAF, one that is more heat tolerant.

 

[johnr]

Now that I have more then 3% degradation, I see one bar going away when I stop for awhile. Charges 16 but when I stop after 20 miles, when I start it, one bar is not there any more. That's it telling me that 5% of energy in not there anymore. So 3% + 5% of degradation after 3 years. Even so, much better then the Leafs.

If that's the case, then the i_MiEV also has a much better SOC meter than the Leaf's. In the Leaf, the SOC meter still shows all bars lit up on a full charge even after significant capacity loss, which means each bar now has fewer miles. I much prefer the i_MiEV's way of displaying it (assuming your observation is accurate of course), so you lose a bar or more as the battery ages but each bar still represents the same number of miles. This makes a big difference especially when you're running low - you see two bars left and you know you have the same remaining range as when it was new and had two bars left!

 

[Malm]

I prefer the Leaf way. In the Leaf there are two gauges, one of them will show you always 12 bars in a full charge and the other will be loosing bars as degradation advances. Yes, in the first gauge, every bar will have less energy. The second shows you the difference relatively to a new one.

And now its different, now (with 3 years and 4 months, 70.000 km) it charges all the sixteen bars like a new one, but every bar has less energy. I think every bar has 10% less energy that when it was new. And it goes from 100% to 0% SoC. The car, now only stops at 0% SoC. An 10% turtle.

I now think that my car has 10% less autonomy then in April 2011. If in april I could do 120 km at 70 km/h, now only 108 km.

 

[Barbagris]

I'm playing with Canion and his log record.

Unfortunately I have had many problems lately for recording long distances (app crashes)

In the last three records I have calculated, with partial consumption of 4.84, 5.80 and 6.19 Ah, my battery an estimated 44.0, 41.42 and 42.68 Ah capacity. If I were to take this last as "good", since the nominal battery capacity is 50Ah, we are talking about a remaining capacity of 85.4% compared to new. If I take the "trip timer" screen (wh out & reg) and calculate with 16 kWh battery, 91.3%; with 16,28 kWh battery (88 cells*3,7 volts*50Ah), 89.7%. I feel the first estimation (85.4%) is better than the others.

But these data are not yet sufficiently reliable; should take a long trip spending virtually all of the battery to have better information.

(27,000 kms / 16,000 mi and almost three years)

 

[jray3]

EVen here in the mild climate of Seattle, 2011 LEAFs are dropping like flies, with owners eagerly anticipating a warranty claim or EVen pushing to achieve that loss of the fourth bar to trigger their subsidized battery replacement. Here's today's victim, a LEAF at 100% SOC and 52 miles RR after 51k miles.

https://www.facebook.com/photo.php?fbid=10208768705959947&set=pcb.1096630197035083&type=3&theater
SOrry folks, but EVen with the duh subsidized replacement and 'Lizard Pack' improvements, I'm happier to have a battery that does at 50k miles what it said it would do new, and looks to continue on for a long time yet.

 

[PV1]

If the specs on the LEV50N cells are true, the cycle rating would give us about a 15 year life before degraded to 80% capacity, if driven a full cycle every day (ignoring calendar life and going by cycle life alone). Even the original LEV50 cells have a lower energy density than most any other EV battery cell out there, so that inherently improves cycle life and current ratings.

Koorz, although I haven't tracked any range or energy statistics like I do for Bear, has a noticeably shorter range, which I think is caused mainly by lithium plating from charging through Michigan winters (Grand Rapids, to be precise). Koorz still has the original pack from January 2012 (pre-dating the updated LEV50N cells). The Yokohama front tires are also having an impact, and when I swapped them between cars, Bear lost about 1.7 miles between full charge and losing the top bar of charge during my drive to work.

Nissan makes a nice car, but Mitsubishi better engineers a car. That's at least been my impression between the LEAF and i-MiEV.

Wonder if CaniOn could do an on-the-fly ETE (Energy to Empty) calculation?

 

[FrostyCanada]

Hello PV1, out of curiosity which batteries does Mitsubishi install in the iMiEV sold in the USA, Canada?

LEV50N, or LEV50

Brian

 

[PV1]

Up until sometime in the summer of 2012, they installed 88 LEV50 cells in the i-MiEV. After that, they were using 88 LEV50N cells. Many of the i-MiEVs sold in the US were built prior to the summer of 2012 (my cars are January and February of 2012, found in the driver's door jamb). However, all 2014 and 2016 models, as well as those of us who had battery packs replaced under warranty have the LEV50N cells.

The main difference between the two cell types is that the N cells are more resistant to heat and may have their cycle life improved.

 

[FrostyCanada]

Hello, and thank you for the information.

We loving our car, but one thing we found weird when we got our new Miev was a warning in the manual saying that you shouldn't expose the batteries to extreme cold (more 7days in a row), but we're like you do realize Mitsubishi that you're selling a car in a country that experiences extreme cold.

I don't know how the batteries will respond to the cold, but we're expecting long life and very good reliabilities from the LEV50N batteries.

Fingers crossed,
Brian.