Porsche Mission E

[mnx]

Looks awesome. Unfortunately I think I read it's going to be ~2000kg... Lighter than a Model S, but a lot heavier than their current crop of sports cars.

Anyways it looks awesome, and when ~2020 rolls around I might have to decide this or the new Tesla Roadster.

 

[WarpedOne]

Can anyone explain how upping the pack voltage has any affect on c-rate? I don't see the correlation.

None, C-rate is an unit that is concerned with amperage.

Higher voltage charging needs higher pack voltage or voltage converters in cars.
Current DC chargers (Chademo,CCS and SC) all 'work' at battery voltage without any voltage conversion.
"Future 800V" chargers will be able to charge at 800V only when the battery has close to 800V nominal voltage. Or the car is equiped with DC/DC converter that converts those 800V down to 400V. And that is a bad move.
That is why there wont be much 800V chargers out there.

If charger lowers its voltage down to 400V, it also halves the power output. Max amps stay the same.

 

[techmaven]

None, C-rate is an unit that is concerned with amperage.

Higher voltage charging needs higher pack voltage or voltage converters in cars.
Current DC chargers (Chademo,CCS and SC) all 'work' at battery voltage without any voltage conversion.
"Future 800V" chargers will be able to charge at 800V only when the battery has close to 800V nominal voltage. Or the car is equiped with DC/DC converter that converts those 800V down to 400V. And that is a bad move.
That is why there wont be much 800V chargers out there.

If charger lowers its voltage down to 400V, it also halves the power output. Max amps stay the same.

That's mostly what I'm saying. The 800V capability has nothing to do with the max c-rate the battery chemistry can tolerate. We can charge faster already if the battery chemistry that allows for specific energy now at 260+ Wh/kg also allows for a charge c-rate of > 1.3 without significant affects on life cycle. Going to a higher voltage does allow for a higher charge rate over the same thickness of charge cable, but that's not really what is holding back faster charge rates in a Tesla at least. A chemistry that can tolerate far higher charge c-rates with the same lifecycle can hold a 120 or 135 kW charge rate for far longer than the current chemistry allows (which is extremely short). Going to 800v is a solution to a problem that doesn't exist right now.

 

[ev-enthusiast]

Porsche showed a concept car for an all electric BEV 4-seater sedan at IAA in Frankfurt (video in German).
Most important quotes from today's interview at IAA with Porsche CEO Matthias Müller:

We have very high technical requirements for driving experience, technology, top speed, range, rechargetime for this vehicle. The goal is very ambitious. It'll take quite some time till the technology for such an ambitious vehicle will be ready to start series volume production. Maybe the technology is ready at the end of this decade.

No comment on price ("premium price like you are used to from Porsche").
No comment on production estimates/numbers, waiting for feed back during IAA.
Sceptic on door opening mechanism and interieur design to be introduced in series volume production vehicle.
BTW Porsche slowed production volume down a bit due to China issues.

 

[WarpedOne]

From what I've heard is that CCS 2.0 developed by Porsche, VW and Audi will support 1000VDC and 250A. That's 250kW of power.

Haven't seen this before.... so, they will build EVs with batteries with 1000V?
If they go with 'common' 400V pack voltage, batteries will only get 100kW.
Yet more hype, throwing arund big numbers, trying to impress common people who understand nothing. And still no half decent EV from any of them.

 

[sandpiper]

That's mostly what I'm saying. The 800V capability has nothing to do with the max c-rate the battery chemistry can tolerate. We can charge faster already if the battery chemistry that allows for specific energy now at 260+ Wh/kg also allows for a charge c-rate of > 1.3 without significant affects on life cycle. Going to a higher voltage does allow for a higher charge rate over the same thickness of charge cable, but that's not really what is holding back faster charge rates in a Tesla at least. A chemistry that can tolerate far higher charge c-rates with the same lifecycle can hold a 120 or 135 kW charge rate for far longer than the current chemistry allows (which is extremely short). Going to 800v is a solution to a problem that doesn't exist right now.

The 800V is significant only to delivery more energy more quickly and you're right... it's doesn't solve the battery c-rate issue.

I think that Porsche is just pulling these specs out of their butts, anticipating that by the time 2018 (earliest) rolls around, the battery tech will be there to support the faster charging. If that happens, the 150kw charging will be significant. I don't think anybody imagines that that prototype is anything other than a (really nice looking!) shell.

On a slightly different tangent, I wonder how the emerg crews will feel about approaching a wrecked car with an 800 volt electrical system. 400V is might kill you. 800V will kill you.

 

[gg_got_a_tesla]

Glad that Porsche/Audi/VW are getting in on the act. After a couple of years of dissing Tesla and electrification - see Winterkorn's statements in the past - the VW group has seen the light (if all these come to production, that is). Kudos to Tesla for waking these sleeping giants up.

 

[lolachampcar]

by the time you get to 400 Vdc, a jump to 800 Vdc is not that big a deal from a safety standpoint. Both will kill you in very short order.

The biggest thing you get with higher voltage are (1) smaller components to handle smaller currents for the same power levels and (2) significantly more efficient use of the batteries as you are charging and discharging at lower "C rates" for a given power level (mentioned earlier by other posters). The down side is that you have fewer cells in parallel so one cell failing has a significantly larger impact on the pack's capacity.

 

[techmaven]

(2) significantly more efficient use of the batteries as you are charging and discharging at lower "C rates" for a given power level (mentioned earlier by other posters).

That's what I'm not getting. I see some of these comments, but I don't get why there is any difference in C-rate. You take a cell with an operational voltage range of 3.1 to 4.15 volts. You string a bunch together to get to a pack voltage of 400v nominal when the cell are at > 4 volts. You string double the number to get to 800 volts at the pack level. Still the same charging characteristics at the cell level. I don't see how this increases c-rate at all. I don't see how this helps the pack charge any faster. What am I missing? If the limiting factor was the thickness of the charging cable, then yeah, increasing voltage makes sense. But we're not limited by the charging cable now and are unlikely to be limited in that fashion by 2018/2019/2020, unless there is some big unknown breakthrough in battery chemistry.

 

[JST]

That's what I'm not getting. I see some of these comments, but I don't get why there is any difference in C-rate. You take a cell with an operational voltage range of 3.1 to 4.15 volts. You string a bunch together to get to a pack voltage of 400v nominal when the cell are at > 4 volts. You string double the number to get to 800 volts at the pack level. Still the same charging characteristics at the cell level. I don't see how this increases c-rate at all. I don't see how this helps the pack charge any faster. What am I missing? If the limiting factor was the thickness of the charging cable, then yeah, increasing voltage makes sense. But we're not limited by the charging cable now and are unlikely to be limited in that fashion by 2018/2019/2020, unless there is some big unknown breakthrough in battery chemistry.

This may be a dumb question (and forgive me if it is), but could you start with a cell that has a higher nominal voltage? And would that impact anything as far as C rate goes? Tesla famously started with commodity cells, but Porsche is (probably) not doing that.

 

[Johan]

This may be a dumb question (and forgive me if it is), but could you start with a cell that has a higher nominal voltage? And would that impact anything as far as C rate goes? Tesla famously started with commodity cells, but Porsche is (probably) not doing that.

All lithium based chemistry has about 4.2V maximum. Alkaline usually is 1.5V or multiples thereof (3,6,9,12).

 

[techmaven]

This may be a dumb question (and forgive me if it is), but could you start with a cell that has a higher nominal voltage? And would that impact anything as far as C rate goes? Tesla famously started with commodity cells, but Porsche is (probably) not doing that.

This paper provides some sketch into the near future of lithium ion cell chemistry:

http://case.edu/cse/eche/daigroup/Journal%20Articles/2013/Xu-Cathode%20materialsfornextgeneration.pdf

The constituent materials determine the possible operational voltage ranges. Thus far, high voltage NMC has failed in lifecycle tests with significant voltage fade:

Can the worlds most promising electric-car battery be saved? - Quartz

This is the current state of research:

BMR Reports - Battery Materials Research

Even if high voltage NMC comes to pass, we're talking 4.7 volts up from 4.1/4.2. I still don't see 800 volts as being something useful - can someone explain other than 800v = 400v * 2 and so it must be twice as good?

I have to assume that these announcements out of the VW group are assuming that LMR-NMC chemistry variants end up working by then, or maybe one of the solid state chemistries will work in production.

I find it a bit disingenuous to show vehicles and specs that there is currently no way of making them... that fundamental research breakthroughs are required in order for them to be made, or the resulting specs would be very far from the concepts shown. You might as well show hover boards.

 

[lolachampcar]

Rated capacity is tied to a given discharge rate. Sometimes it is "1C" and others it is something like "C/10". Internal cell losses are not fixed and tend to increase as you draw more current from the cell. Applying this to discussion at hand and you simply get more usable energy from a given pack if you use half the current draw. Less is lost to cell internal resistance which makes more available to do work.

There is also the added benefit of less loss in the wiring and related electronics but this tends to be but a small fraction of the benefit you get at the cell level as wire diameter and the related electronics are often scaled to the reduced current.

 

[brucet999]

That's mostly what I'm saying. The 800V capability has nothing to do with the max c-rate the battery chemistry can tolerate. We can charge faster already if the battery chemistry that allows for specific energy now at 260+ Wh/kg also allows for a charge c-rate of > 1.3 without significant affects on life cycle. Going to a higher voltage does allow for a higher charge rate over the same thickness of charge cable, but that's not really what is holding back faster charge rates in a Tesla at least. A chemistry that can tolerate far higher charge c-rates with the same lifecycle can hold a 120 or 135 kW charge rate for far longer than the current chemistry allows (which is extremely short). Going to 800v is a solution to a problem that doesn't exist right now.

What am I missing here?

Tesla's battery pack runs modules of cells wired in series, at 4V nominal power each, to operate at 400V, right? With x-many modules the pack can store 85 kWh and charge at C = 1.3 rate for some time without damaging cells. The current at 400V charging potential is divided among the cells in the module so that each stays within safe C rate limits.

Same amperage at twice the voltage delivers twice the watts, so why doesn't it follow that modules of twice the number in series, operating at 800 volts, would still charge at the same C rate but take half as long?

 

[dsm363]

There is already a network of VW, Porsche, Audi dealerships all over the world. It would be a simple matter to install charging stations since they already have large capacity electrical installations and most of them are located in auto malls near major highways.

- - - Updated - - -



IF??? Where have you been for the last 6 years?

Are there dealerships spaced exactly every 160-200 miles along all major highway routes even in the middle of nowhere?

 

[apacheguy]

Nissan tried the dealership model with charging points. It didn't work out. I see no reason for it to work out for Porsche.

 

[mmccord]

I find it a bit disingenuous to show vehicles and specs that there is currently no way of making them... that fundamental research breakthroughs are required in order for them to be made, or the resulting specs would be very far from the concepts shown. You might as well show hover boards.

Like autopilot a year ago?

 

[MartinAustin]

Additional details and photos:

Porsche Mission E Concept puts Tesla Model S in its sights [w/video] [UPDATE]

Also, the 500km range is NEDC - which is always higher than the range determined by the EPA. This car won't actually drive as far as a 90D does today.

The seats make the Tesla Gen #1 seats look comfortable! And that is saying something.

There's a huge "transmission tunnel" running along the center of the cabin floor - even though this car has no exhaust pipes or driveshafts running from front to back. Limited interior space.

I think it's dead in the water.

 

[hiroshiy]

What am I missing here?

Tesla's battery pack runs modules of cells wired in series, at 4V nominal power each, to operate at 400V, right? With x-many modules the pack can store 85 kWh and charge at C = 1.3 rate for some time without damaging cells. The current at 400V charging potential is divided among the cells in the module so that each stays within safe C rate limits.

Same amperage at twice the voltage delivers twice the watts, so why doesn't it follow that modules of twice the number in series, operating at 800 volts, would still charge at the same C rate but take half as long?

I understand what techmaven said. With 120kW charging for example, at 800V you have 150A at the battery. Model S has 333A max. Assuming you have 800V 85kWh pack, at 120kW charging, C rate for this pack is the same as C rate for 400V 85kWh pack. However, 800V pack takes half the amps of 400V pack.

Now these two packs have the same C rates, so same charging taper curve. You don't get faster charging battery pack by making more module serial than parallel.

Thus, to obtain faster charging speed, for example 2x times, you need to bump the battery to 170kWh. I think that's why it weighs 2t - the battery would be over 1t.

Next question is slow performance, if 170kWh battery is assumed.

 

[techmaven]

What am I missing here?

Tesla's battery pack runs modules of cells wired in series, at 4V nominal power each, to operate at 400V, right? With x-many modules the pack can store 85 kWh and charge at C = 1.3 rate for some time without damaging cells. The current at 400V charging potential is divided among the cells in the module so that each stays within safe C rate limits.

Same amperage at twice the voltage delivers twice the watts, so why doesn't it follow that modules of twice the number in series, operating at 800 volts, would still charge at the same C rate but take half as long?

Except at the cell level, voltage is the same. The number of watts in a cell doesn't change. The amperage at the cell level doesn't change. Therefore the c-rate doesn't change.