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Stanton
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Re: The Battery Replacement Thread

Fri Sep 11, 2015 8:02 am

jeremyz wrote:What's going to happen in 2021 when somebody's 24kWh battery from their 2016 Leaf S needs to be replaced under warranty? Is Nissan going to crank up some long dead battery factory to generate old cells that haven't been produced for years? Or are they just going to stick in some new modules in the 2011-2016 battery case?
That's the rub. I suspected they may "stockpile" some 24 kW battery packs since they are committed to it for the "S" trim, but what does that mean way down the line? I refuse to believe that Nissan would toss all of that "EV platform engineering" effort if there wasn't a way to continue to retrofit new modules into old Leafs.
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walterbays
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Re: The Battery Replacement Thread

Fri Sep 11, 2015 11:42 am

mxp wrote:I did read in the recent update for the 2016 Leaf that they had a new clause for the battery warranty...

quoted: "....As evidence of a growing confidence in the 30 kWh battery’s cell chemistry (and the fact it will now take less battery cycles to go further), Nissan warrants battery loss below 9 bars of capacity (70%), for the first 8 years or 100,000 miles (160,000 km) in the US and in Europe. The warranty on the S trim stays consistent with that of the 2015 LEAF, at 5 years or 60,000 miles...."
So they still will replace the battery only if capacity drops to 8 bars in a fixed time - a value much less than 70%, based on a metric (bars) loosely correlated with actual capacity and entirely under control of Nissan software.

In other words Nissan still does not have confidence in their battery chemistry with lack of thermal management. So neither do I.

What would convince me to consider another Nissan car would be a true (pro rata) warranty. I.e., we expect the battery will retain at least 80% capacity for 8 years. If your battery has less than 80% capacity at 8 years Nissan will pay the proportion of the cost of a replacement battery equal to your capacity shortfall.

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mwalsh
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Re: The Battery Replacement Thread

Fri Sep 11, 2015 12:45 pm

walterbays wrote: So they still will replace the battery only if capacity drops to 8 bars in a fixed time - a value much less than 70%, based on a metric (bars) loosely correlated with actual capacity and entirely under control of Nissan software.
That's the way I read it too. Sure you've got more years, but then you also have a larger percentage of the battery within those first 4 bars. It's the 30kWh equvalent of a 24kWh battery pack at 5 years/60k.
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Levenkay
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Re: The Battery Replacement Thread

Fri Sep 11, 2015 12:56 pm

WetEV wrote: As an engineer, I'd want to be somewhat cautious in putting a different battery in an older car. Might be a firmware compatibility problem, or perhaps other issues. The only way to be real sure is to instrument the communications and test over a range of conditions. If this is your car, of course, this is fun. Not so fun when it is a customer's car.

Testing costs money. Even if no changes are needed or unexpected issues turn up.

So is there a positive return on investment? If not, why should Nissan spend the resources on this? Even if there is, this has to be second priority to getting the car with the 30kWh battery into production.

Now, a year or two from now, with larger margin and larger expected sales, the answer might be different. And once the production of the 24kWh battery is ramping down, there may be savings from not supporting the old battery and just switching to the newer technology.

(Disclosure: I once worked in automotive electronics design.)
Hopefully, as more automakers offer EVs, having them use and adhere to an industry-standardized battery module interface will become a competitive advantage. Some suitably detailed generalized model for batteries should be adopted and provided via a standardized interface from the battery pack itself, and the car's electronics should adapt to it. Any module, including those from 3rd party aftermarket vendors, should be capable of plugging on (at least from an electrical point of view) and either work or throw an "incompatible battery" error. It's OK if Brand X battery modules don't perform quite as well as those from the OEM; maybe they're cheaper. Or lighter. Or simply obtainable.

LEAFs already adhere to such a standard for describing their batteries; this lets them plug into the same CHAdeMO DCFC stations that can also charge Souls, i-Mievs, or (via adapter) Teslas. I don't see that it would be such a big stretch to extend whatever battery model is presented to clue CHAdeMO stations in as to how to charge them, so that it can also describe to the car what's available for powering motors.

Valdemar
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Re: The Battery Replacement Thread

Fri Sep 11, 2015 1:28 pm

Levenkay wrote:LEAFs already adhere to such a standard for describing their batteries; this lets them plug into the same CHAdeMO DCFC stations that can also charge Souls, i-Mievs, or (via adapter) Teslas. I don't see that it would be such a big stretch to extend whatever battery model is presented to clue CHAdeMO stations in as to how to charge them, so that it can also describe to the car what's available for powering motors.
No, Chademo is a charging protocol, it has nothing to do with standardizing the battery for the purpose of easy swap.
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Levenkay
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Re: The Battery Replacement Thread

Fri Sep 11, 2015 7:02 pm

Valdemar wrote:
Levenkay wrote:LEAFs already adhere to such a standard for describing their batteries; this lets them plug into the same CHAdeMO DCFC stations that can also charge Souls, i-Mievs, or (via adapter) Teslas. I don't see that it would be such a big stretch to extend whatever battery model is presented to clue CHAdeMO stations in as to how to charge them, so that it can also describe to the car what's available for powering motors.
No, Chademo is a charging protocol, it has nothing to do with standardizing the battery for the purpose of easy swap.
My point is that the CHAdeMO stations are supposed to adapt themselves to a wide variety of batteries; from what was said on one of the EVTV programs, anything from 50V to 500V, and a wide range of currents (although apparently some allegedly CHAdeMO - compliant stations don't actually meet the spec). That's quite a range of adaptability, which I assume is under control of information the charger gets over the CAN pathway. Whether the information presently comes straight from the battery pack as I'm proposing, or from a proprietary computer elsewhere in the car, it proves that the right data model can support the charging of interchangeable battery packs. And it oughtn't be much harder to have the motor drive system adapt itself to the description a modular battery pack gives of its capabilities. Or throw an error. This would be a sensible way for Nissan to take its designs anyway, as it would let them keep pace with what we all hope is rapidly improving battery technology.

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Re: The Battery Replacement Thread

Mon Sep 14, 2015 11:02 am

The loose and coarse 4 bars loss requirement, always concerns me.What is to say that the first 4 bars are matched to 50% of the capacity, and not 70%?

70% of 107 is 75 miles, or a usable range of 65 miles EPA.
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Re: The Battery Replacement Thread

Mon Sep 14, 2015 11:31 am

I don't much like the marketing math, either. Saying that Nissan will replace the battery if capacity drops below 70%, knowing that the firmware won't extinguish the fourth capacity bar until the battery reaches 64-66% capacity is dishonest.

-Karl (66.00%)

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Re: The Battery Replacement Thread

Mon Sep 14, 2015 1:37 pm

kolmstead wrote:I don't much like the marketing math, either. Saying that Nissan will replace the battery if capacity drops below 70%, knowing that the firmware won't extinguish the fourth capacity bar until the battery reaches 64-66% capacity is dishonest.
I think Nissan's answer here is that what we've identified as SOH in the CAN with our unsanctioned tools like LeafSpy is not "really" SOH. But of course they won't share how they measure it.

If push comes to shove, it seems range testing the car should be an unambiguous way to determine if they're really lying about the 70% figure. The usable capacity of a new pack is fairly well-established (although I'm not sure there's an official Nissan source on this) as a bit more than 21 kWh. So we could conservatively say that if you have 70% capacity you should have at least .7 * 21 = 14.7 kWh available.

Test the car by doing a 100% charge then resetting the trip odometer and efficiency meter. If you can only drive 56 miles (until shutdown - not just turtle) at 4.0 miles / kWh, then that means your usable capacity was only 14 kWh. Now of course "4.0" on the dash could mean anything from 3.95 to 4.049, so the capacity would be between 13.8 and 14.2 kWh - multiple range tests could remove some of that error in measurement. I could imagine Nissan even complaining about this approach - saying that range could be affected by weather, e.g. But if several such tests are done in warm weather and consistently show less than 70% of the expected miles achieved, that seems to me to be fairly irrefutable evidence that Nissan's full of crap.

-Mike (65%)
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dhanson865
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Re: The Battery Replacement Thread

Mon Sep 14, 2015 1:51 pm

kolmstead wrote:I don't much like the marketing math, either. Saying that Nissan will replace the battery if capacity drops below 70%, knowing that the firmware won't extinguish the fourth capacity bar until the battery reaches 64-66% capacity is dishonest.

-Karl (66.00%)
Good point, we don't know anything about the number and granularity of bars on the new leaf. Will it be 12 bars + 0 bar like on the 2011-2015 Leafs? Will the first bar be ~15% or will it be a higher capacity bar 12 to make degradation less noticeable or will they go for more even bar values to make it easier to understand?
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