Question About 4680 Cells

[Bob Anderson]

I've always been curious about this slide from Battery Day. The 54% range increase and 56% $/KWH reduction shown, are these increases able to be stacked on top of each other?

Take a current M3 that now costs $10,000 for a battery (just a guess) w/ a 300 mile range. W/ the 4680 cells, would you now be able to get a range of over 1,050 miles for the same $10,000 battery cost? Or the same 300 mile range car for only $2,857 (vs $10,000) battery cost? The range increase and cost reductions by themself are mind-blowing, but stacked together makes it even more impressive.

I guess what I'm looking for is what is the 4680 range increase for an equivalent current 2170 KWH battery cost? That would answer my question from the slide below.

 

[Crissa]

No, they don't stack, They happen simultaneously.

So you get ~50% more range and ~50% less cost potentially.

That's not a thousand miles by any stretch. That would give the Model 3 Long Range a 529 mile range at a $35K price tag.

-Crissa

 

[Dids]

I've always been curious about this slide from Battery Day. The 54% range increase and 56% $/KWH reduction shown, are these increases able to be stacked on top of each other?

Take a current M3 that now costs $10,000 for a battery (just a guess) w/ a 300 mile range. W/ the 4680 cells, would you now be able to get a range of over 1,050 miles for the same $10,000 battery cost? Or the same 300 mile range car for only $2,857 (vs $10,000) battery cost? The range increase and cost reductions by themself are mind-blowing, but stacked together makes it even more impressive.

I guess what I'm looking for is what is the 4680 range increase for an equivalent current 2170 KWH battery cost? That would answer my question from the slide below.

Range is a function of moving mass. Doubling the battery size doubles the weight which decreases range.
The optimum battery would be no larger than ~300 miles of range (this optimal range was long established by gas vehicles). This perfect battery would need to recharge in ~10 min.
In other words. Putting a larger battery decreases miles/kwh, it decreases efficiency. Doubling the battery does not double the range. It increases the time spent recharging!

 

[Ogre]

Doubling the battery does not double the range. It increases the time spent recharging!

Having a bigger battery is less efficient but does not increase the time spent recharging when you are on the road.

Tapering will quickly rob any charge speed advantage the 300 mile battery has over the 500 mile battery. If you are adding 250 miles range (about 80% range on a Model Y), when you roll away from the charger, the charge rate is going to be about 50kW.

Charging a 500 mile range battery to that same 250 miles range means you unplug at a 50% state of charge and the charge rate is 110kW. Even though you've pushed more energy into the battery, staying to the left side of the tapering curve longer means you add miles of range faster.

You also don't need to double the battery size to double the car's range.

Unless there is some fundamental change which reduces that tapering curve, you won't see that 10 minute recharge adding 200+ miles unless you have a 500 mile battery.

Sorry to ramble, this is one of the reasons I am leaning towards the tri-motor Cybertruck.

 

[JBee]

I've always been curious about this slide from Battery Day. The 54% range increase and 56% $/KWH reduction shown, are these increases able to be stacked on top of each other?

Take a current M3 that now costs $10,000 for a battery (just a guess) w/ a 300 mile range. W/ the 4680 cells, would you now be able to get a range of over 1,050 miles for the same $10,000 battery cost? Or the same 300 mile range car for only $2,857 (vs $10,000) battery cost? The range increase and cost reductions by themself are mind-blowing, but stacked together makes it even more impressive.

I guess what I'm looking for is what is the 4680 range increase for an equivalent current 2170 KWH battery cost? That would answer my question from the slide below.

The easiest way to do this is to compare the cost per kWh for a 2170 and a 4680 cell.

According to Cairn Energy a Tesla 2170 cell battery pack costs around $156kWh. If a 4680 if 56% less cost it would be around $87kWh.

The largest 82kWh battery in a M3 would cost $12 792 in 2170 cells.
That same 82kWh battery would cost (82x$87kWh) $7,134 in 4680 cells.

So for $12792 (the cost of the 2170 battery) you could buy (12792/$87kWh) a 147kWh 4680 battery.

I hope this answers your question. ;-)

 

[ajdelange]

I guess what I'm looking for is what is the 4680 range increase for an equivalent current 2170 KWH battery cost? That would answer my question from the slide below.

Does equivalent mean equivalent in cost or capacity? In either case it's impossible to answer the question as we don't know what Tesla is going to do. We can push a couple of numbers around though. For the same battery cost the new tech will evidently give us 1/0.56 = 1.785 times more kWh and, thus, approximately 78% more range. But Tesla won't do that. They will put in just enough of the new batteries to give us 300 or 500 miles range and either pocket the savings or reduce the sales price or some combination of the two.

 

[Bob Anderson]

Does equivalent mean equivalent in cost or capacity? In either case it's impossible to answer the question as we don't know what Tesla is going to do. We can push a couple of numbers around though. For the same battery cost the new tech will evidently give us 1/0.56 = 1.785 times more kWh and, thus, approximately 78% more range. But Tesla won't do that. They will put in just enough of the new batteries to give us 300 or 500 miles range and either pocket the savings or reduce the sales price or some combination of the two.

The over 1,000 mile range in my original post I'll admit is completely unnecessary, more just laying out my thought process. I imagine there'll be a slight increase in range, and even more significant decrease in price. Price I'd argue is more important at this point.

Now... If only we knew what the charging rate will be!

 

[ajdelange]

Now... If only we knew what the charging rate will be!

That's pretty easy to take a stab at. It's going to be about 1C, that is, you will be able to take on 50% charge in about half an hour. Thus half an hour will get you about 150 miles in the AWD and about 250 in the TriMotor.

This is clearly a rough estimate and also it needs to be recognized that the first 10% (0 to 10% SoC) will go a lot faster than 1.0C and that the last 10% (90 - 100% SoC) will go a lot slower but what you really want to know is how long you will have to be at a charger to add 200 miles to the battery. That's going to be about 2/3 hr in the AWD and 2/5 hr in the Tri.

As charging speed seems to be a hot area of competition right now the overall rate may turn out to be over 1.0C, perhaps 1.2C - 1.3C. There are cars being sold now that charge at those rates. Tesla now seems to have the self confidence or arrogance or whatever you want to call it to ignore this to some extent. They know 300 - 400 is plenty of range (that's more than my Lexus has) and that half an hour to 40 min at a SC is quite acceptable. As long as they are selling more cars than anyone else they can afford to maintain this posture. In the future things may change.

 

[CyberGus]

Those figures are for the cells, not the pack. Even if the cells were free, the pack itself would still have a non-trivial cost.

 

[Dids]

Having a bigger battery is less efficient but does not increase the time spent recharging when you are on the road.

Indeed it does! You are exchanging less frequent charging for longer charging.
EG.
Both CT2 & CT3 start with battery at 80%. They leave the same location at the same time.
CT2 range =240 miles
CT3 range=400 miles

I don't know the battery pack sizes for the 2 trucks but let's use 400w/mile which gives.
CT2= 120kwh pack
CT3=200kwh pack
And I'm setting them equally efficient which you agree is not possible since ct3 must be heavier and therefore requires more energy....

They both charge their batteries to 80% at a 250kw fast charger. both stop when their battery is 20%.
Ct2 drove 192 miles @ 65mph for 177minutes
Ct2 charges for 14.4 minutes
He is 3.2hrs into his trip
Ct3 drove 320 miles @ 65mph for 295minutes
Ct3 charges for 24 minutes
He is 5.3 hrs into his trip.
CT2 continues to drive for another 2 hrs. when he reaches 320 miles he charges at the same supercharger that ct3 is charging at.... he is 5.2 hrs into his trip. he has 23% battery remaining. After charging for 12 min both him and ct3 pull out at the same time both of them have 80% battery and are 5.3hrs into their trip.
The only difference is. CT 2 stopped to refill twice and Ct3 driver has a UTI....?

This scenario is not accurate though.... in reality both trucks will not charge at exactly the same continuous rate... and CT3 must be less efficient... but if they are identically efficient and they both charge at the same rate then bigger battery only means less frequent fills.

 

[CyberGus]

Indeed it does! You are exchanging less frequent charging for longer charging...

You're actually exchanging for longer charging and less efficiency, due to the extra weight.

 

[ajdelange]

You're actually exchanging for longer charging and less efficiency, due to the extra weight.

If we assume, based on ABRPs estimate of 420 Wh/mi that the TriMotor battery is 210 kWh and the 300 mi AWD is 126 kWh and that the 100 kWh battery in the S weighs 2240 kg and so we estimate the weights of the batteries as 1.3*2240 = 2912 kg for the AWD and 2.1*2240 = 4704 kg. We can then estimate the rolling resistance loads as
AWD: 0.01*2912*9.8*1063/3600 = 84.3 Wh/mi
Tri: 0.01*4704*9.8*1063/3600 = 136.1 Wh/mi

Thus the TriMotor will consume 51.9 more Wh/mi than the AWD which is 12.3% of the 420 Wh/mi total
If the promised improved specific energy improvements are realized in these new batteries then, of course, the impact of the larger pack will be less.

Now charging time for a given delta SoC should not be effected based on average 1C rate provided, of course, that you use a charger that can deliver 1C. A 150 kW (V2) or 70 kw (urban) supercharger clearly cannot deliver and average charge rate of 210 kW and the average rate will be less than 1C for the Trimotor. But the Trimotor and AWD should charge at about the same rate from a V3 SC and presumably those will be supplanting the V2s over time.

Looking at time required to replace X miles it is apparent that one would need to allow about 12.3% longer for the Trimotor based on the assumed 12.3% increase in Wh/mi for the extra battery weight.

You can't hold me to these exact numbers, of course. They aren't supposed to be accurate predictions but rather indications of what one might expect.

 

[Ogre]

You are exchanging less frequent charging for longer charging.

You are skewing the numbers in favor of the dual motor by requiring the tri motor have much more range in the tank at the end of the trip. If you had both trucks end the dat with the same range, the CT3 would have had more than enough time for an extra bathroom stop. Or more likely would have just added a bathroom stop at the same Supercharger the CT2 driver stopped at.

I ran a sampled trip on a real route I've taken. The default setting in ABRP has the CT3 at the same efficiency as the CT2 so I lowered it's efficiency by more than 10% and it still arrives more than half an hour before the CT2.

Literally any route you pick, the CT3 will be just as fast or faster than the Ct2. Tapering has a much bigger effect on range than the ~10% or less efficiency loss you are going to get from that extra range.

This all ignores the fact that the longer range means you are more likely to stretch the distance a bit so you can only use the higher speed 250kW chargers. Also... skipping a single congested Supercharger can easily shave you 20-30 minutes of a trip.

 

[Ogre]

You're actually exchanging for longer charging and less efficiency, due to the extra weight.

At your home charger or a destination charger where tapering doesn't come into play, you are 100% correct. But I really most people aren't worried if their truck takes 4 hours or 5 hours to charge in their garage. When you are on the road going between Superchargers, tapering has a massive effect on charge rates and that's when you care about charge speeds most because you are sitting there waiting for it.

A typical Supercharger stop, you roll in with 30 miles range left and you charge up to whatever mileage you need to hit the next charger +10%

If you charge the CT2 from 30 miles up to 240 miles. Your average Rate of charge is 100 kW. You start around 150kW and at 80% state of charge your battery only accepts power at 50kW.

If you charge the CT3 from 30 miles up to 240 miles. Your average rate of charge is 130 kW. You start around 150kW and at 50% state of charge your battery only accepts power at 110kW.

The effect tapering has on your charge speed is much higher than the 10% or so efficiency loss you will see.

 

[Dids]

You are skewing the numbers in favor of the dual motor by requiring the tri motor have much more range in the tank at the end of the trip. If you had both trucks end the dat with the same range, the CT3 would have had more than enough time for an extra bathroom stop. Or more likely would have just added a bathroom stop at the same Supercharger the CT2 driver stopped at.

I ran a sampled trip on a real route I've taken. The default setting in ABRP has the CT3 at the same efficiency as the CT2 so I lowered it's efficiency by more than 10% and it still arrives more than half an hour before the CT2.

Literally any route you pick, the CT3 will be just as fast or faster than the Ct2. Tapering has a much bigger effect on range than the ~10% or less efficiency loss you are going to get from that extra range.

This all ignores the fact that the longer range means you are more likely to stretch the distance a bit so you can only use the higher speed 250kW chargers. Also... skipping a single congested Supercharger can easily shave you 20-30 minutes of a trip.

No. They both start with 80% charged battery and they both leave the charger at 320 miles with 80% charge. I didn't end the trip they keep going forever.... and I did say that it wasn't reality since the rate of charge is unknown as is the battery size as is the efficiency gap due to the weight.... I just pointed out if you hold both equal then a larger tank doesn't speed up your trip.