Does the 70D have new batteries and will the 85D become a 100D?

[thegruf]

but notice also the S70D is only 329hp = 2x 165hp?

this could indicate the 221hp motor running with less volts (and presumably a smaller inverter too)

 

[LargeHamCollider]

I posted this in the "does the the EPA range make sense" thread before seeing this thread, it probably belongs here.

Because range gives us efficiency which varies with mass, the rated range of the new 70D is the only real (if a bit shaky) data we have to determine whether or not the new 70D uses a new cell chemistry. New cells means mass very close to old 60, old cells mean significantly more mass.

Efficiency of old line up:
208 miles on 60 kWh (60) = 3.467 miles per kWh
265 miles on 85 kWh (85) = 3.118 miles per kWh
270 miles on 85 kWh (85D) = 3.176 miles per kWh

Efficiency of the new 70D:
240 miles on 70 kWh (70D) = 3.429 miles per kWh

If it does not use a new cell chemistry then it's efficiency should be about 10/25ths of the way between the efficiency of the old 60 and the S85 plus (270/265 -1)% to account for dual drive or 3.390 miles/kWh.

If it *does* use a new cell chemistry then it's efficiency should be about equal to the efficiency of the old 60 plus (270/265 -1)% to account for extra dual drive efficiency or 3.532 miles/kWh. Actual efficiency is 3.429miles/kWh, closer to the "old chemistry" number. I think this gives some evidence in favor of the "old chemistry hypothesis" but not enough to definitively call it one way or another.

credit to arijaycomet who I copied the initial efficiency calculations from.

 

[Cottonwood]

but notice also the S70D is only 329hp = 2x 165hp?

this could indicate the 221hp motor running with less volts (and presumably a smaller inverter too)

The 85D has an advertised horsepower of 422 HP or 211 HP per motor. The 70D has an advertised horsepower of 329 HP or 165 HP per motor. Power in a resistive load is V[SUP]2[/SUP]/R. If we use a resistive equivalent for the motor (excuse handwaving), then the power should scale as Voltage Squared. The Voltage ratio between the 60 and the 85 was 14/16 (module number) or 7/8.

211 HP * (7/8)[SUP]2[/SUP] = 162 HP

That is close enough for me to bet on the 70D having the same number of modules as the 60 (same pack Voltage as the 60) with either more cells per module or improved cells. My wild guess would be more cells per module to transform the 60 battery to a 70.

If we see a near zero State of Charge Supercharger charge rate on the 70D of 105 kW, then the pack Voltage in the 70D is the same as the 60. Initial charge rate in both the 85 and 60 were about 120 kW and 105 kW and limited by the 330 Amps max on a Supercharger. 105=120*7/8

 

[Saghost]

The 85D has an advertised horsepower of 422 HP or 211 HP per motor. The 70D has an advertised horsepower of 329 HP or 165 HP per motor. Power in a resistive load is V[SUP]2[/SUP]/R. If we use a resistive equivalent for the motor (excuse handwaving), then the power should scale as Voltage Squared. The Voltage ratio between the 60 and the 85 was 14/16 (module number) or 7/8.

211 HP * (7/8)[SUP]2[/SUP] = 162 HP

That is close enough for me to bet on the 70D having the same number of modules as the 60 (same pack Voltage as the 60) with either more cells per module or improved cells. My wild guess would be more cells per module to transform the 60 battery to a 70.

If we see a near zero State of Charge Supercharger charge rate on the 70D of 105 kW, then the pack Voltage in the 70D is the same as the 60. Initial charge rate in both the 85 and 60 were about 120 kW and 105 kW and limited by the 330 Amps max on a Supercharger. 105=120*7/8

Clever thinking. This supports my expectation that the 70 is an 85 pack minus the front two modules - which simplifies Tesla's logistics at the same time as well.

 

[CHG-ON]

I just don't know why. But something about this change and upgrade strikes me as odd. Range increase seems middling. Power increase...meh. Perhaps it may be a harbinger of some significant range increases coming down the road. Battery swap anyone?

 

[trond.strom]

Clever thinking. This supports my expectation that the 70 is an 85 pack minus the front two modules - which simplifies Tesla's logistics at the same time as well.

So assuming 3% efficiency loss from batteri to motor and 14 modules in s70d 16 modules in s85d and p85d we hve the following

	motor	kWp	kWp to motor	kWp from battery	Battery size kWh	C	# of cells	Wp per cell
S70D	522	389,3	245,7	253,071	76,08	3,33	6216	39,53
S85D	522	389,3	314,8	324,244	86,95	3,73	7104	44,31
P85D	737	549,6	514,8	530,244	86,95	6,10	7104	72,47

Using 3% loss from battery to motor confirmes the 325kWp draw reported on the s85d

Using the Wp per cell number the amperage draw per cell would be 10,98 12,31 and 20,13 respectively which all seems reasonable.

Since battery chemistry and energy storage varies quite a bit betwen cells I would also expect the 70d pack to be using cells screened out with lower than 3400mah this would probably enable Tesla to accept cells from producers with less strict quality controls

 

[GregRF]

Interesting. I was expecting the other obvious approach - 14 S85 modules = 76 kWh using your math, while eliminating the need to manufacture/stock S60 modules.
Walter

Why not 13 S85 modules = 70.6kWh?

 

[Saghost]

Why not 13 S85 modules = 70.6kWh?

Mostly because we have a precedent for 14 modules (which is what the 60 kWh pack has,) and changing modules changes voltage. It could be that everything can handle a still lower voltage without issues, but I don't know - and even if it works, it would mean slower Superchargers - which have a 330A limit as well as power limits.
Walter

 

[mgboyes]

The 85D has an advertised horsepower of 422 HP or 211 HP per motor. The 70D has an advertised horsepower of 329 HP or 165 HP per motor. Power in a resistive load is V[SUP]2[/SUP]/R. If we use a resistive equivalent for the motor (excuse handwaving), then the power should scale as Voltage Squared. The Voltage ratio between the 60 and the 85 was 14/16 (module number) or 7/8.

211 HP * (7/8)[SUP]2[/SUP] = 162 HP

That is close enough for me to bet on the 70D having the same number of modules as the 60 (same pack Voltage as the 60) with either more cells per module or improved cells. My wild guess would be more cells per module to transform the 60 battery to a 70.

If we see a near zero State of Charge Supercharger charge rate on the 70D of 105 kW, then the pack Voltage in the 70D is the same as the 60. Initial charge rate in both the 85 and 60 were about 120 kW and 105 kW and limited by the 330 Amps max on a Supercharger. 105=120*7/8

See Fascinating and intriguing power/performance figures on the TM website for info on the power of the individual motors (which is much higher than you think).

 

[mhpr262]

Yes but in reality you'll see step changes let's say every 3 or 4 years where capacity increases, corresponding to an average improvement of 3-5% per year.

I'm not saying it's impossible that there's a new chemistry in the 70 kWh cars, Im just saying to me it's very unlikely and the explanation I suggested above (just filling up the pack more) is way more likely to be true. Occam's razor and all that...

The batteries in the first 2012 cars needed thorough testing, so they are 2010/2011 tech. Three or four years later would be ... right about now!

Also, Occam's Razor works both ways here. We know that new cell tech WILL inevitably supersede the old one and it must be tested, too. So what better way to do this than in the car with, most likely, the lowest sales numbers, and thus teh lowest risk in case of a recall, in the Model S line-up? The 400 mile roadster is already a good indication of what to expect. To me it seems perfectly logical that they would try out the new cells in the roadster first, then take it one step further and ramp up production with the 70D.

 

[scaesare]

The batteries in the first 2012 cars needed thorough testing, so they are 2010/2011 tech. Three or four years later would be ... right about now!

Also, Occam's Razor works both ways here. We know that new cell tech WILL inevitably supersede the old one and it must be tested, too. So what better way to do this than in the car with, most likely, the lowest sales numbers, and thus teh lowest risk in case of a recall, in the Model S line-up? The 400 mile roadster is already a good indication of what to expect. To me it seems perfectly logical that they would try out the new cells in the roadster first, then take it one step further and ramp up production with the 70D.

The next-gen Roadster cells would seem to be less energetic than current Model S cells, much less what would be needed if the 70D was garnering it's additional capacity from more energy-dense cells.

 

[glhs272]

Hate to be a party pooper... but likely curb your enthusiasm. How they got from 60 to 70 kWh was by putting in cells where there was earlier just ballast in the 60 pack. Probably no new chemistry. The 85 pack is already full.

So with all the back and forth when the 70D was released about being a new chemistry or not... I was predicting it was a new chemistry.... So now that the 90kwh pack has been released and has been confirmed that it was new chemistry, does the 70 pack also contain the new chemistry (just not disclosed)?

 

[Johan]

So with all the back and forth when the 70D was released about being a new chemistry or not... I was predicting it was a new chemistry.... So now that the 90kwh pack has been released and has been confirmed that it was new chemistry, does the 70 pack also contain the new chemistry (just not disclosed)?

Don't you think they would have said so on the call, if that was the case?!?

 

[spottyq]

So with all the back and forth when the 70D was released about being a new chemistry or not... I was predicting it was a new chemistry.... So now that the 90kwh pack has been released and has been confirmed that it was new chemistry, does the 70 pack also contain the new chemistry (just not disclosed)?

It seems to me the majority was in agreement to say that the 70kWh uses 14 of the same exact modules that the 85kWh uses. (The 85kWh has 16 modules.)
Previously, the 60kWh battery also had 14 modules, but they were of lower capacity (some cells were replaced by ballast.)

As I remember it (sorry — too tired to check up the links now), the evidence we had was an 85kWh pack disassembly by a forum user, then a picture of the disassembly of a 60kWh module by some official agency (NTHSA?), and supercharging screenshots of the 60, 70 and 85 (which gives us the battery voltage, thus the number of modules.)

 

[S'toon]

I'm pretty sure I read somewhere that the 70D battery pack had more cells, replacing some of the "ballast" cells that were in the 60.