SageBrush
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Re: Nissan "Out-of-Warranty" support for battery pack degradation

Thu Nov 30, 2017 7:41 am

GRA wrote:Guess I was lucky to learn on a stick

Same here. Not only was my early driving on a manual, I lived in a VERY hilly city at the time. Down-shifting on steep declines is second nature to me. The terrain also taught people to leave a generous distance from the car ahead at stops since some drivers would slip the better part of a car length backwards before going forward.

Those were the days: three pedals and a hand brake -- all synchonized -- for effective driving. Nowadays I only have to put a pinch of pressure on the steering wheel once in a while so the car knows I am still awake.
2013 Model 'S' with QC & rear-view camera
Bought off-lease Jan 2017 from N. California with 63.9 Ahr after 22k miles
Car is now enjoying an easy life in Colorado

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abasile
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Re: Nissan "Out-of-Warranty" support for battery pack degradation

Thu Nov 30, 2017 10:29 am

I have no doubt that many people drive down mountains without even considering the need to use engine braking. In many cases, they are probably the same people who slow to 30 mph for curves (on a road with a 55 mph limit) and fail to use turnouts. Virtually anyone who drives up and down (or down and up) regularly, however, quickly learns to avoid riding the brakes.

So, I picked up the LEAF at the dealer yesterday and brought it back home. I did have an opportunity to meet with the head LEAF technician at the dealer and discuss my concerns with him. While I truly appreciated his conscientiousness, candor, and diligence, I felt that he was too willing to let Nissan off the hook.

Initially, the technician ran diagnostics on the car and found nothing wrong. I'm sure Nissan considers the behavior of our car, at a battery capacity of "nine bars", to be "normal". At the end of the day, and I really have to give him credit for this, the technician reports that he performed a "road test" by driving our LEAF home to his residence in another mountain town which is roughly 1000 feet lower than our home yet about two miles further away from the dealer. He reported being nervous about the range of the car, understandably so!

The following morning, on a pretty low charge (it couldn't have been any higher than roughly the "low battery" warning or so), the technician descended the mountain. Although the battery would have cooled overnight (I don't know whether the LEAF was garaged or not), the first 3.5 miles or so of his drive would have involved both descending and ascending (little net elevation change), a bit more than my 2.0 miles of descending/ascending before my big descent. His ensuing descent would have then been about 3550' over 12.2 miles on CA-138 and CA-18, versus 4800' over 16 miles on CA-330 to CA-210 for the main portion of my descent.

The technician reported that regenerative braking worked fine for him during the first ten minutes or so of his descent, and then faded out. Even at a pretty low state of charge, though, there was no available regenerative braking as he got closer to the bottom of the mountain. He reported that he took the descent slowly (he reports being a very conservative driver) and did not have an issue with the brakes shuddering. I would note here that, all the way down the mountain from the junction of CA-138, CA-18 has two lanes in each direction and it's easier to simply stay in the right lane and take the descent slowly. CA-330, the road we take when leaving our mountain community, has a single lane of travel and more pressure to maintain the flow of traffic at 45 - 55 mph during commuting hours.

The technician told me that he believes Nissan never intended the LEAF to be used for going up and down mountains, and that regenerative braking was not intended as a substitute for engine braking. He said it was his understanding that the LEAF limits the amount of regeneration in order to keep the motor/generator from becoming hot, and that the motor may have to work harder to charge a degraded battery. There may be a grain of truth here, but really I don't buy this explanation. Would 15 - 20 kW of regen be any harder on the motor than fast freeway driving?

Anyway, my response was that our LEAF's regenerative braking worked quite well when the car was newer. I added that there's never been anything in Nissan's literature for the LEAF which suggests that the LEAF may have issues with long downgrades, and he concurred with that. Here I'll also add that California, the number one state for EV sales, is quite mountainous and millions of people have relatively easy access to big grades. I'm not aware of other EVs having issues with mountain descents, unless of course the battery is close to fully charged but that's the user's fault. The technician said that the 2017 LEAF has a much improved battery, but based on the reports I've read here of excessive degradation of 30 kWh packs, I'm doubtful.

My next step may be to contact Nissan's EV support line again.
2011 LEAF at 71K miles, pre-owned 2012 Tesla S 85 at 98K miles
LEAF battery: 9/12 bars and < 49 Ah (-28% vs. new)
Tesla battery: 250+ miles of range (-5% vs. new)

Joe6pack
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Re: Nissan "Out-of-Warranty" support for battery pack degradation

Thu Nov 30, 2017 11:14 am

FWIW, when my battery degraded, I lost a great deal of regen as well. I rarely had more than the first two bubbles of regen available unless I was in the red on charge. Because I live where it is relatively flat, this was never an issue from a braking standpoint. However, it did annoyingly contributed to further reduced range.
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Valdemar
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Re: Nissan "Out-of-Warranty" support for battery pack degradation

Thu Nov 30, 2017 2:04 pm

Leaf has oversized brakes for the size of car it is and even larger cars. Sure it is heavier than other cars of the same size, but the overheating concern while not unfounded is likely not much to be worried about unless we are talking about race track like driving down the mountain. After all even when the car was new leaving home on a full charge was a guarantee not to get any regen all the way down.
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abasile
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Re: Nissan "Out-of-Warranty" support for battery pack degradation

Thu Nov 30, 2017 3:49 pm

Valdemar wrote:Leaf has oversized brakes for the size of car it is and even larger cars. Sure it is heavier than other cars of the same size, but the overheating concern while not unfounded is likely not much to be worried about unless we are talking about race track like driving down the mountain.

While Nissan is to be commended for giving the LEAF larger brakes, I would have to disagree about brake overheating. It is a very real concern for anyone descending a big mountain in a LEAF with a degraded battery. As our LEAF technician demonstrated, loss of regen on a nine bar LEAF is less of a problem if descending on a very low charge (at around "low battery" warning or below) and a warmer battery. But if I want to descend our mountain at 50-60% SOC and four temperature bars, the brakes do overheat and start to shudder. That's true even if I drive well below the speed limit (I've tried virtually everything).

There are multiple problems with having to descend the mountain at a very low SOC:
1. Occasionally, there are emergency road closures (due to rockslides, fires, or serious accidents) that necessitate turning around. I always prefer to leave enough charge to be able to make it back home, or off the mountain via an alternate route.
2. We wouldn't be left with much charge to drive around after completing the descent.
3. We don't normally leave the car sitting at low SOC (see 1, above); it gets charged most nights and/or early mornings. When our LEAF was newer, I usually charged it to 60-70% or so, in order to strike a good balance between available regen, efficiency, and range. That doesn't work now!

Valdemar wrote:After all even when the car was new leaving home on a full charge was a guarantee not to get any regen all the way down.

Yes, but anyone with a basic understanding of EVs shouldn't be surprised by that.

Note that I'm not asking for the 2011 LEAF to be an ideal mountain car, as it never was. I do, however, think it's unreasonable to have such poor regen. I'd be more satisfied if, in regenerative braking, Nissan allowed the same amount of power as when using a DC Fast Charger.

By the way, even at close to 90% charge, our 2012 Tesla Model S usually allows about 30 kW of regen when descending. That's probably commensurate with what a Supercharger would provide at that SOC. On most days that we need to leave the mountain, I charge the Model S to 75% and it gets up to about 81% at the base of the mountain.

Honestly, with respect to our LEAF, I'd probably be fine writing this off as an experiment with mixed results, but it seems that Nissan is continuing to sell cars with battery packs that degrade rapidly and leave their owners with very poor regen.
2011 LEAF at 71K miles, pre-owned 2012 Tesla S 85 at 98K miles
LEAF battery: 9/12 bars and < 49 Ah (-28% vs. new)
Tesla battery: 250+ miles of range (-5% vs. new)

SageBrush
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Re: Nissan "Out-of-Warranty" support for battery pack degradation

Thu Nov 30, 2017 4:55 pm

How does the technician 'take it slow' down his hill without using brakes ?
Perhaps by starting the descent at a particularly slow speed ?

Too bad he did not drive your route, or measure the rotor temperatures.
The good news is that he noted complete loss of regen on the descent. That should be enough to show that the LEAF is not safe going down steep descents since the car only has friction brakes at that point, as opposed to friction brakes plus regen in a normally operating LEAF
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Bought off-lease Jan 2017 from N. California with 63.9 Ahr after 22k miles
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abasile
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Re: Nissan "Out-of-Warranty" support for battery pack degradation

Thu Nov 30, 2017 5:20 pm

SageBrush wrote:How does the technician 'take it slow' down his hill without using brakes ?
Perhaps by starting the descent at a particularly slow speed ?

I don't think he normally drives a LEAF to work, or at least not a degraded LEAF.

In our LEAF, the technician did have regen for the first part of the descent, and due to a Nissan software quirk, there's generally more regen available at slower speeds. In addition, CA-18 does have some sections where the grade is pretty gentle. That said, he most definitely did need to use the friction brakes. Had his descent been much longer, I expect the brakes would have started to shudder.

SageBrush wrote:Too bad he did not drive your route, or measure the rotor temperatures.
The good news is that he noted complete loss of regen on the descent. That should be enough to show that the LEAF is not safe going down steep descents since the car only has friction brakes at that point, as opposed to friction brakes plus regen in a normally operating LEAF

While it would have been ideal if he had driven my route, I'm grateful he made the effort that he did. Yes, he did establish that, even at a very low SOC, the LEAF lost all regen significantly before completing a 3500' descent. And my main descent is about 4800'.

Of course, the standard response seems to be that this is "normal".
2011 LEAF at 71K miles, pre-owned 2012 Tesla S 85 at 98K miles
LEAF battery: 9/12 bars and < 49 Ah (-28% vs. new)
Tesla battery: 250+ miles of range (-5% vs. new)

SageBrush
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Re: Nissan "Out-of-Warranty" support for battery pack degradation

Thu Nov 30, 2017 7:06 pm

"Normal" just means typical.
Yeah -- a typical, defective LEAF
2013 Model 'S' with QC & rear-view camera
Bought off-lease Jan 2017 from N. California with 63.9 Ahr after 22k miles
Car is now enjoying an easy life in Colorado

DaveinOlyWA
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Re: Nissan "Out-of-Warranty" support for battery pack degradation

Thu Nov 30, 2017 8:40 pm

regen is reduced to keep from burning up the motor? Is the speed of fast charging reduced as well? Seems like a downhill descent like that would not heat up much of anything besides brake pads. So the motor should be nice and cool.

I mean his explanation doesn't make any sense at all. I could see a reduced level of regen like no more than 20 kw but no regen at all? That is a bad programming decision and nothing more

LEAF Spy added temp reading for inverter and or motor I think. are you seeing excessively high temps on your logs?
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abasile
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Re: Nissan "Out-of-Warranty" support for battery pack degradation

Thu Nov 30, 2017 8:58 pm

DaveinOlyWA wrote:LEAF Spy added temp reading for inverter and or motor I think. are you seeing excessively high temps on your logs?

My OBD adapter doesn't appear to be working, so I haven't checked. LEAF Spy is great, but we haven't found it necessary for routine driving.

However, I agree that it makes no sense to blame the motor temperature for bad regen. Particularly if I've only been driving for ten minutes and the ambient air temperature is about 45 F.

I can understand regen limitations when the battery is cold, but as long as it's possible to charge the car on L2, there should be at least some regen. Plus it should be possible to offset the heater consumption.
2011 LEAF at 71K miles, pre-owned 2012 Tesla S 85 at 98K miles
LEAF battery: 9/12 bars and < 49 Ah (-28% vs. new)
Tesla battery: 250+ miles of range (-5% vs. new)

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