Why the LEAF Gen 2 and not the 220 miles Tesla Model 3?

GetOffYourGas said:

lorenfb said:

GetOffYourGas said:

So we are talking about two different things. Allow me to elaborate. Your numbers are looking at different C rates for the same battery. I was comparing the C rates for two different batteries. Like, for instance, a 30kWh Nissan battery and a 60kWh Tesla battery.

Let's assume both are 360V.

1C of a 30kWh battery (360V * 83.3Ah) = 83.3A
C/2 of a 60kWh battery (360V * 166.6Ah) = 83.3A

Both batteries output the same amount of current, despite having different C rates, due to the different capacities.

P = I^2 * R
Assuming again that both batteries have a 60mOhm internal resistance, they both have a power dissipation of 416W.

Click to expand...

Consider a 60kWh battery as being two 30kWh batteries in parallel. The result also affects the effective output
impedance of the combined batteries (a 60kWh resulting battery). It's now 1/2 of the single 30kWh battery.
The combined battery can obvious supply 2X the current output of the original 30kWh.

So driving at the same speed for either a single or parallel 30Ahr (60Ahr) battery results in the same power consumption,
as would be expected. Also, the total heating effect of the 60Ahr battery will be less than the single 30Ahr battery,
i.e. the lower output impedance of the 60Ahr battery.

Example - 2 parallel 30kWh

P (for each) = (I/2)^2 x R
P (for combined (60kWh)) = 2 x (I/2)^2 x R) = I^2 /2 x R = I^2 x R/2

That is P = 1/2 the 30kWh battery losses for the 60kWh battery.

Click to expand...

Yup, I'm with you now. We definitely started with different assumptions. You reasoning makes sense. In the end, though, a 2x battery would have 1/2 the heating, not 1/4, as you just showed.

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Did you overlook this?

That is P = 1/2 the 30kWh battery losses for the 60kWh battery.

Click to expand...

A 60kWh battery is a 2X a 30kWh battery and would dissipate 1/2 the original power of the single 30kWh
by itself supplying all the power, right?

The equations above also indicate that if you actually did combine (not practical) two 30kWh batteries to
make a 60kWh battery, each would dissipate 1/4 (as noted by Reg & indicated above) each's original power.
Remember, all the 'new' powers need to sum correctlly whether you actually did use two 30kWh batteries
or a single 60kWh battery.

lorenfb said:

GetOffYourGas said:

Yup, I'm with you now. We definitely started with different assumptions. You reasoning makes sense. In the end, though, a 2x battery would have 1/2 the heating, not 1/4, as you just showed.

Click to expand...

Did you overlook this?

That is P = 1/2 the 30kWh battery losses for the 60kWh battery.

Click to expand...

Click to expand...

No, you misunderstand me. I did not state myself clearly. I was saying that you just showed that the heating would be 1/2 and not 1/4. I am exactly agreeing with this quote.

Earlier in this thread, the claim was made that it would be 1/4.

SageBrush said:

BrockWI said:

Pulling a battery at 1C vs at C/2 is roughly four times the heat generated internally.

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Reference ?

Click to expand...

I think we just picked this problem apart and found that a 2x battery discharged at C/2 will produce 1/2 the heat as compared to a 1x battery discharged at 1C.

GetOffYourGas said:

lorenfb said:

GetOffYourGas said:

Yup, I'm with you now. We definitely started with different assumptions. You reasoning makes sense. In the end, though, a 2x battery would have 1/2 the heating, not 1/4, as you just showed.

Click to expand...

Did you overlook this?

That is P = 1/2 the 30kWh battery losses for the 60kWh battery.

Click to expand...

Click to expand...

No, you misunderstand me. I did not state myself clearly. I was saying that you just showed that the heating would be 1/2 and not 1/4. I am exactly agreeing with this quote.

Earlier in this thread, the claim was made that it would be 1/4.

SageBrush said:

BrockWI said:

Pulling a battery at 1C vs at C/2 is roughly four times the heat generated internally.

Click to expand...

Reference ?

Click to expand...

I think we just picked this problem apart and found that a 2x battery discharged at C/2 will produce 1/2 the heat as compared to a 1x battery discharged at 1C.

Click to expand...

My original post:

P (for each) = (I/2)^2 x R
P (for combined (60kWh)) = 2 x (I/2)^2 x R) = I^2 /2 x R = I^2 x R/2

Click to expand...

The first equation indicates 1/4 power for each 30KWh when used in parallel to produce a single 60kWh;
P = (I/2)^2 X R = I^2 X R divided by 4

Yes it is half the total heat generated, but assuming two separate 30 kWh packs (unrealistic I know) each of those packs would be 1/4 as hot as a single 30 kWh pack would be, ignoring ambient heating. Realistically it would be a single 60 kWh pack that would get 1/2 the heat.

lorenfb said:

GetOffYourGas said:

lorenfb said:

Did you overlook this?

Click to expand...

No, you misunderstand me. I did not state myself clearly. I was saying that you just showed that the heating would be 1/2 and not 1/4. I am exactly agreeing with this quote.

Earlier in this thread, the claim was made that it would be 1/4.

SageBrush said:

Reference ?

Click to expand...

I think we just picked this problem apart and found that a 2x battery discharged at C/2 will produce 1/2 the heat as compared to a 1x battery discharged at 1C.

Click to expand...

My original post:

P (for each) = (I/2)^2 x R
P (for combined (60kWh)) = 2 x (I/2)^2 x R) = I^2 /2 x R = I^2 x R/2

Click to expand...

The first equation indicates 1/4 power for each 30KWh when used in parallel to produce a single 60kWh;
P = (I/2)^2 X R = I^2 X R divided by 4

Click to expand...

It seems you are having trouble with me agreeing with you. I don't understand why you are pushing this? You misread my (admittedly poorly written) statement in which I agreed with you. And when I clarify where the 1/4 figure came from (someone else - not you), you pull up an older post of yours in which you state 1/2. Seems defensive from this end of the 'net and I'm wondering why.

GetOffYourGas said:

lorenfb said:

GetOffYourGas said:

No, you misunderstand me. I did not state myself clearly. I was saying that you just showed that the heating would be 1/2 and not 1/4. I am exactly agreeing with this quote.

Earlier in this thread, the claim was made that it would be 1/4.



I think we just picked this problem apart and found that a 2x battery discharged at C/2 will produce 1/2 the heat as compared to a 1x battery discharged at 1C.

Click to expand...

My original post:

P (for each) = (I/2)^2 x R
P (for combined (60kWh)) = 2 x (I/2)^2 x R) = I^2 /2 x R = I^2 x R/2

Click to expand...

The first equation indicates 1/4 power for each 30KWh when used in parallel to produce a single 60kWh;
P = (I/2)^2 X R = I^2 X R divided by 4

Click to expand...

It seems you are having trouble with me agreeing with you. I don't understand why you are pushing this? You misread my (admittedly poorly written) statement in which I agreed with you. And when I clarify where the 1/4 figure came from (someone else - not you), you pull up an older post of yours in which you state 1/2. Seems defensive from this end of the 'net and I'm wondering why.

Click to expand...

Sorry for the back-and-forth, and also sorry if I caused you to get a headache too.

BrockWI said:

Yes it is half the total heat generated, but assuming two separate 30 kWh packs (unrealistic I know) each of those packs would be 1/4 as hot as a single 30 kWh pack would be, ignoring ambient heating. Realistically it would be a single 60 kWh pack that would get 1/2 the heat.

Click to expand...

Great, everyone's on the same page.

So a 60 kWh battery will heat up half as much as a 30 kWh battery?

Sorry for being crappy at physics.

internalaudit said:

EatsShootsandLeafs said:

Because I can't help myself, I thought I'd look into this more.

Here is a nicely detailed write up from a guy with a 2015 Leaf. The 2015 Leaf has a supposedly better heat-resistant battery than the early models. In two years and 14k miles he has a 10% range reduction. http://www.wind-works.org/cms/index.php?id=84&tx_ttnews%5Btt_news%5D=4464&cHash=92313192ff5b7949bd2086ad0bbfc94d

He says "This isn’t out of line with what others have seen.".

As for Tesla, a big matrix here shows that the average model s has projected loss of 23 miles over 100k (10%), with an actual loss reported of just under 6% @ 66k combining all results.
https://www.teslacentral.com/worried-about-tesla-battery-degradation-its-23-miles-every-100000-driven

The tesla data is more reliable because it's a large pool of drivers.

I don't know if relative geography of leaf and tesla is the same, but I imagine it's similar.

One of the teslas after 60k miles had a range reduction from 265 to 264. Anybody think any leaf can do that? The worst, and this was a significant outlier, had a 10% reduction after 54k miles.

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Does the Tesla data include battery degradation for battery packs that Tesla had replaced?

I have read a couple of comments over on TMC as well as additional information from a friend who has a Model S that Tesla proactively replaces components that it thinks may fail.

Maybe it's like the old Rolls Royce where there are very few customer complaints because RR fixes the issues and word doesn't go out about them?

I'm not biased for or against Tesla or Leaf but just want to make some informed decision making when it comes to buying a BEV, in late 2018 at the earliest.

Click to expand...

well from the chart, its easy to pick out the ones that live in Mojave and Phoenix...

The one consistent parameter is time so having driven 100,000 miles and seen 1% degradation is easy if in a decent climate and you drive 10,000 miles a month.

Can I say my 10/2016 build date 30 kwh pack is bullet proof because I have gone over 22,000 miles with zero quantifiable degradation? That extrapolates to 1% over 100,000 miles, right?

So the graph tells half the story, a story we know but most do not.

Here is more extensive and up to date data from the Tesla owners Battery Life database:

https://docs.google.com/spreadsheets/d/t024bMoRiDPIDialGnuKPsg/edit#gid=154312675





As related to battery age (notice the scale -- this one starts at 85% SoC):
Average 94% SoC remaining after 5 years. Also note that after the first ~ 5% loss further degradation is negligible

SageBrush said:

Here is more extensive and up to date data from the Tesla owners Battery Life database:

https://docs.google.com/spreadsheets/d/t024bMoRiDPIDialGnuKPsg/edit#gid=154312675

As related to battery age (notice the scale -- this one starts at 85% SoC):
Average 94% SoC remaining after 5 years. Also note that after the first ~ 5% loss further degradation is negligible

Click to expand...

http://www.mynissanleaf.com/viewtopic.php?f=6&t=24433&start=100

Joe6pack said:

Still nonsense. The oldest car on that graph is 4.5 years old with the vast majority being less than three years old. We all know from the LEAF that time and charging cycles play an enormous part in degradation. In fact, it's interesting that several Tesla's on that graph have lost more than 10% in the first couple of years.

BTW, that graph has been floating around for several months now. Wonder if they will ever update it. I kind of doubt it.

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Just like LEAF owners there are Tesla owners that abuse their packs. Some drive then to almost 0 and charge to 100% and leave it there for days. Other charge only from 90-100% ever day and only use the top 10%, I see this quite a bit at superchargers. I Have also seen 2014 Models with 100K plus mies and almost no degradation. In general the packs hold up very well. I think the 3 and the LEAF G2 comparisons are a bit off, the cars are too different in too many ways and the group of people deciding between these two models is a very small subset of the large number of Tesla buyers.

For those that may have missed or overlooked the up-thread post of comparative per cell internal
impedance of Tesla (present MS/X 18650 cell) versus Leaf 1; Tesla - 59 mohms, Leaf - 12 mohms.
So for any given battery load current, e.g. supplying rolling resistance (weight/tire size) energy,
each Tesla cell's internal impedance will consume 5X the energy and generate 5X the heat than
will the Leaf's cell, i.e. for the same cell current. Therefore, each Leaf cell is 5X as efficient as is
the 18650 cell in the Tesla.

Note: The overall battery impedance for both the Tesla (80kWh) and Leaf (24kWh) is about the same
(56 - 60 mohms).

Since the Tesla battery has about 3.5X more parallel cell 'legs' than the Leaf's battery and neither
the Model S nor X is 3.5X heavier than the Leaf, the extra power loss won't approach 5X. But since the
overall output impedance is about the same for both the Leaf and the Tesla, and the Model S is about
1.4X the weight of the Leaf, the Model S will be using about 1.4X the battery current of the Leaf at the
same speed just for rolling resistance losses. Since battery loss power is equal to I^2 X R, the Tesla will
develop about 2X the battery heat as the Leaf will at the same speed just for rolling resistance losses.
That's one reason why the Tesla battery requires TMS, notwithstanding cell instability.

Data from here: https://rennlist.com/forums/mission-e/984855-probable-base-price-2.html

Note: Obviously each Tesla cell will dissipate less power than each Leaf cell.

The chart shows packs with more than "100% of original range"

so if we want to make Tesla longevity look REALLY good, we just need to load up the database with a bunch of hypermilers?

DaveinOlyWA said:

The chart shows packs with more than "100% of original range"

so if we want to make Tesla longevity look REALLY good, we just need to load up the database with a bunch of hypermilers?

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No

Driving has NOTHING to do with the RM range meter.
This is really not that hard. The RM reading is functionally equivalent to the fully charged Ahr battery capacity reading from LeafSpy in a LEAF, albeit multiplied by a constant.

I didn't think you are stupid -- are you just trolling ?

Anecdotal: I'll update the plot.
After 1635 days, my 2013 Model S85 stood at 95.3% of original capacity. And I'm no hypermiler.
After roughly the same period of time, my 2011 LEAF was at 77% of capacity (which is pretty good for SoCal).

Also, lifetime miles/kWh in the LEAF is about 3.4
Lifetime miles/kWh in the Tesla: 3.0

So driving the Tesla costs me about 13% in efficiency losses. (So worth it, BTW).

I will still test drive a LEAF gen 2 ASAP but for me it's clearly not a a good value if I can get a Model 3 within a year.

sparky said:

I will still test drive a LEAF gen 2 ASAP but for me it's clearly not a a good value if I can get a Model 3 within a year.

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But why, if you truly believe you can purchase a Model 3 for the same price and; greater range, better battery life,
more features, and "prestige"? Why even minimize one's self like those of us 'having to hide' when at a light next to
a Tesla and having to endure a "marginal BEV" - the Leaf?

sparky said:

Anecdotal: I'll update the plot.
After 1635 days, my 2013 Model S85 stood at 95.3% of original capacity. And I'm no hypermiler.
After roughly the same period of time, my 2011 LEAF was at 77% of capacity (which is pretty good for SoCal)...

Click to expand...

So, nominal pack capacity loss of your LEAF as reported by its BMS (LCB) was .23 X 24 kWh, or ~5.5 kWh

And nominal capacity loss of you Tesla pack,reported by its BMS was 4.7 X 85 kWh, or ~4 kWh.

Using more accurate methods of measuring pack capacity loss would probably show that 2013 Tesla packs lost kWh capacity faster, on average, than 2011 LEAF packs in similar climates over identical miles and time of use, but since Tesla has never allowed independent testing to assess its pack capacity losses, we likely will never know.

By hoarding kWh in an over-sized pack, you can easily reduce its percentage of capacity loss, but the kWh loss benefits gained by lower kWh throughput and gentler cycling will tend to be overcome by calendar losses suffered by the entire pack.

I expect the "60 kWh" LEAF pack using passive thermal management to be very close in total and available capacity to the "55 kWh" liquid cooled Tesla three pack, and that both will show substantially identical rates of capacity loss, both as a percentage and also in kWh loss, over time and miles driven.

But I expect to buy neither of those cars, as the LEAF "40 kWh" pack is likely to be a superior option.

I was quite impressed with my 2011 LEAF's performance in the 864 mile trip it made last week to the LEAF events in the bay area, other than my slight disappointment in not losing the ninth capacity bar.

If a "40 kWh" leaf pack losses available kWh capacity at the same rate as my 2011 has, ~0.8 kWh per year (as measured by range test results and recharge capacity, NOT by using the LBC estimate) the the useful life of the pack will almost certainly exceed that of the rest of the car.

sparky said:

Anecdotal: I'll update the plot.
After 1635 days, my 2013 Model S85 stood at 95.3% of original capacity. And I'm no hypermiler.
After roughly the same period of time, my 2011 LEAF was at 77% of capacity (which is pretty good for SoCal).

Also, lifetime miles/kWh in the LEAF is about 3.4
Lifetime miles/kWh in the Tesla: 3.0

So driving the Tesla costs me about 13% in efficiency losses. (So worth it, BTW).

I will still test drive a LEAF gen 2 ASAP but for me it's clearly not a a good value if I can get a Model 3 within a year.

Click to expand...

That's pretty amazing because the Model S has 3.5X the power of the Leaf, and is a heavier car. That's one of the great things about EV. You take any ICE car with 107 horsepower and compare it to a 300+ horsepower heavier car and yet the heavier one only burns 13% more power and you win an award!

lorenfb said:

sparky said:

I will still test drive a LEAF gen 2 ASAP but for me it's clearly not a a good value if I can get a Model 3 within a year.

Click to expand...

But why, if you truly believe you can purchase a Model 3 for the same price and; greater range, better battery life,
more features, and "prestige"? Why even minimize one's self like those of us 'having to hide' when at a light next to
a Tesla and having to endure a "marginal BEV" - the Leaf?

Click to expand...

It's interesting that I wrote that hypothetical scenario about pulling up to the lights in a model 3 next to a leaf some weeks ago and you're still going back to it. I wonder if it hurts because it's so true.

The Leaf is a decent hatchback that would fit in well with other hatch backs like a Golf or a subaru imprezza. But, the Model 3 doesn't look out of place parked next to a BMW or a Lexus IS. Different class of car, really. The model 3 will clearly be more expensive, because it's a ton more car.

If we're honest with ourselves, and by God we should be, this thread is a bit like "What should I get a BMW X3 or a Nissan Rogue?" Certainly nobody thinks the Leaf is as much car as the Model 3. Surely. But, the Tesla does clearly charge more for being more.

EatsShootsandLeafs said:

The Leaf is a decent hatchback that would fit in well with other hatch backs like a Golf or a subaru imprezza. But, the Model 3 doesn't look out of place parked next to a BMW or a Lexus IS. Different class of car, really. The model 3 will clearly be more expensive, because it's a ton more car.

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The Model 3 starts at $36k delivered. Other than the glass roof which I am going to buy as an extravagance, in my opinion the only option I would really miss in the base package is DRCC. The 40 kWh LEAF is ball-park the same price as a model 3 with DRCC, so to me one choice could be between a markedly inferior EV with DRCC Vs a much better EV without DRCC.

The bottom line: I cannot imagine buying a new LEAF. The silver lining is that their inferior battery tech leads to depreciation that outpaces the actual loss of performance so a used LEAF can be a good deal for an informed consumer.