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Preference of LFP vs NCA for hot areas (like Phoenix)?

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These aren't bad questions.

I also plan to keep my car for 20+ years. I have a 2014 Model S, so it obviously has the NCA battery. I knew more of the general things like not sitting at extremely low or high states of charge for a long time. Some of that more recent data I've been seeing from people here about keeping the car really near 40 or 50% to be most ideal sounds fine on paper, but I'm just not going to do that, because it's kind of an annoying and impractical way to use my car. I think this is where the 80/20 rule in life applies to this as well as most things. I am getting a reasonable amount of benefit by doing what is mostly good and avoiding the worst case treatment of the battery. That is good enough without having to stress and worry about it all the time.

And my wife and I recently had a talk about battery replacement or car replacement. With wk057 coming out with the battery warranty plans for older cars, we talked about should we get that warranty? Should we sell this car while it still is working perfectly before the battery fails? We came down to that I really love how this car is. It is grandfathered into the permanent data plan and permanent Supercharging. And we are going to keep it for as long as we possibly can, so we will just go with whatever comes--not get the warranty and probably just do a replacement whenever it happens. And we decided to go with the other way--keep this 2014 Model S and replace the old 2005 Honda Civic Hybrid with a new Model Y.

My daily driving should typically be 50 miles with occasional longer drives. Keeping to a 20% DOD should be no problem and charging to 50 or 60% whatever isn't an issue. I feel since my driving is kind of minimal, as in not many long commutes, I have a lot of flexibility in my charging options.

That's pretty cool about the grandfathering part. I think it will be interesting when battery replacements become more commonplace and hopefully not so expensive. I thought about replacing both cars with EV's, but that's a bit too bold for me :). We like to do camping and need at least 1 ICE vehicle around for more remote trips. Definitely would like to try camping in a Model Y once though just for fun.
 
I understand they don't just stop working, but since the rate of degradation once it reaches that magic number is not linear, you might as well consider it EOL for estimation purposes.

I'm trying to learn if I can control the rate of degradation meaningfully by adopting the best charging habits. So, determining what are the best charging habits and how do those correlate to between the NCA and LFP (are they the same) and lastly, does the AZ heat affect either of those differently.

And you hit the nail on the head wrt cycles on LFP's. Is that why LFP cycles counts are touted over NCA because they know you'll NEED more cycles due to the lower capacity battery? OR, do NCA's really degradate faster than LFP's so after a few years they are really the same capacity battery?
You can control the rate of degradation by adopting best charging habits as discussed previously; that is true. But remember there is a level of uncertainty in all cells and it is also luck of the draw sometimes even with following best practices. AZ heat is not "good" for either of the chemistries as compared to say New England. Best practices would also be to not park in direct sunlight and park where the ambient temperature is lower than the outside (i.e. garage). I live in SC and park in my garage at home and the parking garage at work instead of the surface level lot for this reason among many others as direct sunlight wears out paint, interior, etc. - they have free chargers also :)

For a simple math calc, the LFP has an EPA range of 272 miles while the LR is 358 miles. In order for the LR to have the same benchmark energy (or rated miles) as the LFP, it would have to degrade over 24% (1 - 272/358). That is also assuming the LFP model would have zero degradation in that same time period, which of course is unrealistic as it would have at least some. So while an NCA chemistry will certainly degradate more than an LFP chemistry would, the amount of "punch" an LFP has won't ever top an NCA chemistry even with meaningful degradation (IMO).

The LFP serves a specific purpose for Tesla: it costs less. That is prefect for a shorter range vehicle at a lower price point.

I have linked the master thread on battery health and life below as well:

 
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Interesting discussion. Spend half the year south of Tucson and now have a MY LR AWD, just turned back our Bolt ($35,700 from GM) yesterday and ordered a M3 SR LFP model a couple of weeks ago (timing was good!).

My questions are basically the same as posed by the OP at the start of this thread, plus a couple of others:


Would it be best to charge to 100%, leave the M3 unplugged till it gets down to around 50% SoC and charge up again to 100% SoC?

If I should leave the M3 for six months at a time (in a garage in Tucson) I've been trying to determine if leaving it at 50% SoC is the proper thing to do. I cannot imagine leaving an EV at 100% SoC, LFP or not, especially during a Tucson summer!!

Thoughts?

Rich
 
Would it be best to charge to 100%, leave the M3 unplugged till it gets down to around 50% SoC and charge up again to 100% SoC?
Never charge to 100% unless you are going on a road trip and need the full battery capacity. Best to keep it at 80% max or even lower if your daily driving doesn't take you very far each day. My daily commute is around 25% total each day so I only charge to 50-60% each day. You certainly have more leeway with an LFP model then with an NCA LR model, but there is still no reason to charge to 100% unless you need it.

If I should leave the M3 for six months at a time (in a garage in Tucson) I've been trying to determine if leaving it at 50% SoC is the proper thing to do. I cannot imagine leaving an EV at 100% SoC, LFP or not, especially during a Tucson summer!!
Leave it plugged it and set to 50% charge level. This is the best practice for storage.
 
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My assessment of charging best practices, for NCA chemistries...
  • Tesla's battery management system (BMS) requires a quiescent vehicle for some of its calibrations. So let the car sleep as much as possible. Resist the urge to wake the car to check on it. Note that the Tesla mobile app will always wake the vehicle. Some others, like Tessie and TezLab, have settings to avoid waking the car. And note that none of this affects actual battery health... only BMS reporting.
  • Heat is the greatest enemy of battery cell health, and will accelerate degradation faster than anything else. Whenever possible, park the vehicle in cool ambient conditions. Keep Cabin Overheat Protection on.
  • Higher states of charge induce voltage stress to battery cells. A 100% SOC equates to ~4.2v/cell and provokes significant stress. Reduction of voltage/cell proceeds in a roughly linear fashion equating to lower SOC's, with steadily improving life cycle counts. At ~3.92v/cell little further improvement in life cycle counts are seen. 3.92v/cell equates to ~60-65% SOC. So using 65% SOC as a charge ceiling, wherever practicable, is advised.
  • Depth of discharge (DOD) induces permanent internal resistance in the cells, resulting in lower capacity. The difference between a 10% DOD and a 100% DOD is very significant - approximately two orders of magnitude in terms of life cycle counts. A 10% DOD is not very practical, of course. But shallow DOD's are to be encouraged wherever possible.
  • Related to DOD, extended charge sessions where the SOC is significantly bumped cause more cell stress than do multiple, shallower charge sessions.
  • Whereas cold temperatures are preferable for cell health on a static basis, those temps are not ideal when charging or discharging the battery (which, of course, includes driving). Preheat the battery via climate control settings for ~30 minutes in cold weather. Note that cabin temp will rise and stabilize much, much faster than will battery pack temp. And note that charging the cells in cold temps also induces stress. If at all possible, avoid charging a vehicle with a cold pack until pack temperature can be raised.
  • Elevated charge rates (C-rate) induce cell stress. This, along with the heat that accompanies it, is the reason that frequent SuperCharging sessions will introduce some additional level of pack degradation.
  • Elevated discharge rates (C-rate) induce cell stress. This is not really a factor for most people, as most of us don't have an environment in which extended discharging is possible. But if someone were doing lots of track days, or spending lots of hours driving at high speeds, then it could be a factor. Conversely, a car driven in Chill mode over its lifetime is likely to see better battery health, all else being equal.
My sense is that NFP chemistries are far closer to a set-it-and-forget-it kind of use paradigm. Much/most of this doesn't apply. Their upside is easier use and longer lifecycle. Their downside is poorer capacity and efficiency. And weight. They simply don't store as much energy/mass as NCA.
 
And you hit the nail on the head wrt cycles on LFP's. Is that why LFP cycles counts are touted over NCA because they know you'll NEED more cycles due to the lower capacity battery? OR, do NCA's really degradate faster than LFP's so after a few years they are really the same capacity battery?
An LFP battery with 3/4 the capacity of an LNCA battery will need 4/3 the cycles for the same amount of energy charged and discharged.

However, an LFP battery is likely to get far more than 4/3 the cycles of an LNCA battery before each has only 80% capacity.

Of course, an LNCA battery with 80% capacity still has more than an LFP battery that started with 3/4 (75%) of the LNCA battery's capacity. But the LNCA battery was more expensive the begin with, and the continuing faster degradation may eventually leave it with less capacity than the LFP battery over the very long term.
 
You are misinterpreting the graph. The battery doesn't just stop working at 1500 cycles. The graph is showing the remaining full capacity of the battery (as compared to original capacity). You will notice the the graph stops at 80% of the original capacity. So you can easily get 1500 cycles out of the battery, the question is how much degradation will there be.

And yes, lower DoD (in theory) increases the # of cycle counts. You also must take into account the LFP battery has less energy available. So while the LFP battery may withstand more cycles, those cycles are taking you less miles around town than a similar cycle with an NCA battery.
When reading the research we see that both battery manufacturers and researchers use 80% remaining capacity as the end of life degradation level. The reason is that at about 80% remaining (20% degradation) the degradation process most often has reach the level where the battery start loosing much more. A degradation curve can be quite straight until the 80% level where it bends downwards and the degradation after that point happens quicker. This is not always the case, as the conditions can affect that. But mostly the batteries is done at that point. I would think that teslas 70% remaining is set to that level, to be sure the most of the "battery is used up" and the battery really need replacement by then(and of course, haveing only 70% of the speced range is a factor as well.
 
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I think you’re overthinking one aspect of economically owning a car long-term at the expense of everything else.

I have a 2016 Model S 75 that I plan to keep a long time. It is currently brushing 140k miles, with about 88% of its original capacity/range remaining. So far the battery and drive unit have been rock solid after the initial relatively steep degradation. It’s been nearly flat for 2 years now.

I purposely spec’d the car in a way that I thought would minimize long-term repair and maintenance. No air suspension. No sunroof. RWD instead of AWD because that’s one less drive unit to worry about out of warranty. I realize not all of that applies to the 3 but the principle would generally apply. These are the sorts of things I’d be adding to the calculation.

In the end though, it sure seems like most batteries fail due to dumb luck and not as the result of any meticulous care or reckless abandon. At least in the S/X, it’s not usually the cells that go - it’s the electronics, BMBs, coolant lines, etc etc etc.

Mostly I think you’re torturing yourself over something that really has no binary answer that is going to satisfy you.

Get the car you’re actually going to enjoy getting in and driving for the next 20 years. That’s a long time to be stuck listening to a shitty stereo.
 
There is also an element of uncertainty in the batteries as some people baby the battery like crazy and still have a good amount of degradation.

I know I think different than many other here on TMC. My thoughts come from reading a lot of research. The research shows that degradation is quite predictable.

I think there is many cases where people think that 80% SOC is the best SOC to keep the car at, hence ”I did everything I could and still have high degradation”.

My car have shown very high range and no appearent degradation on the range and still higher battery capacity than many new M3P have. I did know that this is most probably not true. From my own calculations, where I started the capacity at 82.1kWh (full pack when new and about what the EPA-test showed), I should be around or slightly above 3% degradation today. That would be 79.5 kWh or so.
Remember, this is not a very precise calculation but the spread in degrsdation in research is low. The highest source of error is my average SOC and average cycle size.

So with a NFP of 80.9kWh, I knew that this is probably not true. Two earlier tests did not change the NFP, running down to 3% and 0.39% SOC and leave the car at that SOC overnight did not change the NFP.

Last sunday I arrived from a long trip and planned to have low SOC at home. I had a full charge nit long before this trip.
I drove the car down to -2% SOC and let it stand overnight before charging.
The next morning the NFP had dropped to 79.4kWh. This is very close to my calculations. I think this is very close to my batterys current capacity.

From my pount of view, I was not lucky in the battery lottery when it comes to the degradation. Maybe, maybe I was lucky getting a battery with ”full” initial capacity but for the degradation from delivery to today, my battery follows the main principle for NCA calendar + cyclic aging.

There is one UK member which has a low NFP on his M3P, it started low so maybe unlucky with the capacity. (China built with the 82.1-pack).
Despite this it seem to not loose any capacity now when he use the low SOC principle.

I still have to be a bit humble about being completely wrong, but so far more or less every sign or data points to that the research / science is correct…
 
I purposely spec’d the car in a way that I thought would minimize long-term repair and maintenance. No air suspension. No sunroof. RWD instead of AWD because that’s one less drive unit to worry about out of warranty.

I guess that's what I'm trying to do between NCA / LFP choices. Try to minimize downstream costs... Is the LFP a better long term choice because 1) it may last longer due to cycle count and 2) if I do have to replace it, will it be less expensive because it's an overall cheaper battery and 3) if it is more heat tolerant
 
Very interesting thread. Main reasons I bought a Tesla are for performance and wanted an EV better than the other company we had.

For me it would be hard pass on the LFP RWD ones. One they came out with the LFP versions the 0-60 times went from about 5.2 to 5.8. That with a fully charged battery. So other than fresh off the charger at 100% it is likely to be slower. So if I want a slow EV, I have a lot of other options besides Tesla that would qualify for some sort of incentive.

I also appreciate AWD so the long range versions were an easy decision for me. RWD may be at times more fun to drive but given the power Teslas can put down, AWD means I can exercise the throttle with a big more enthusiasm. Also I would think the RWD would be hell on rear tires with all the torque just sent through them.

As for acceleration boost - worth every penny of it. Added it to 2 cars so far and don't regret the purchase a single time.

Finally - give Teslas spotty build quality and expensive out of warranty repairs (when they happen), I am looking at 5-6 year life cycle and then I'll move on to a new model with Tesla or another company. Mostly because I hope there will be real advancements in autonomous driving.
 
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