With "design priority", I mean that there are a lot of possible features for a PEM that they could do research & development for, but they will need to focus there efforts on the most important ones. That, I think, is currently the over-all efficiency of the car (for the alpha builds apparently around 300 Wh/mile), so I think the design of the power train will prioritize that, and that other features (like the one TEG explained) may get added in future development.
Aha.
Modern AC drives have been around for about twenty five years and have about 97% efficiency already. There are no easy pickings there. Support for three phase AC charging using the motor drive, on the other hand, is a big, sweet fruit ready for picking and within reach.
You seem to be referring to this:
Electric vehicle network Information, Electric vehicle network Article & Encyclopedia Resource - iReference.ca
Apparently a canadian website (not necessarily the most informed about Mennekes) without an "About us".
Referring to an "interim report" from NPE, it says:
This is the "interim report" on charging infrastructure. It's in German, which is why I linked to an English-language summary. It's written by a VDE task force. VDE is the German equivalent of IEEE
(see wikipedia). They have been given the task of planning Germany's future EV infrastructure by the German government. Angela Merkel personally attended the opening session.
This is the main site of the interim report.
Again, you see that 3-phase will go up to 44 kW, whereas for 60 kW, the charging method is DC (expecting the latter post 2020). General expectation on this forum is that Tesla will be interested in charging speeds even higher than that, already for the mid-2012 Model S.
Furthermore, this "interim" report is merely talking about what is "considered possible", and about the "introduction" of 44 kW in "2014-2017".
I see this source basically as a confirmation that these plans are not interesting for Tesla as a fast-charging method replacing DC.[/URL]
Please take a deep breath, then go back and re-read my posts
I have never suggested that AC should replace DC for quick charging. What I have been arguing for years is that support for three phase is absolutely crucial, and that DC is too expensive to take its role. They have different niches, and both are needed. I have also said that J1772 is useless outside of the regions where high power single phase is common, and that CHAdeMO is too weak.
I will try to summarize.
DC is great for really high power charging, where the regenerative drive isn't powerful enough. This is somewhere around 50 kW, but the high cost of external DC chargers probably means that cost/benefit considerations only make DC charging attractive at around 100 kW and above. In practice, I expect that in Europe, the cutoff of AC charging will be at 44 kW, due to the standardized 400 V/63 A circuit size. I seem to remember that 480 V/80 A is a standard circuit size in the US, which might be why Tesla (I seem to recall) announced 480 V/80 A capability for Model S. I'm currently unable to find references for this last bit, but the exact amperage is really a minor point anyway. But references to Model S being able to charge from "a 480 V outlet" are easy to find. I really hope that Tesla Motors are not such dishonest weasels that they say "from a 480 V outlet" to the press when they mean "from a $50,000 external DC charger connected to a 480 V outlet".
DC is useless for charging at power levels that can be handled by the motor drive directly, because the car contains all the major components needed internally anyway, and the DC charger needs a three phase grid connection anyway. If the DC charger delivers the same amount of power that the motor drive could have handled by itself, there is significant cost and zero benefit. This ratio improves as delivered power increases above the capability of the motor drive, but remains unimpressive until DC power reaches at least twice the power of the regenerative circuitry. That would be somewhere around 50 kW for a small car, 100 kW for a large one. If CHAdeMO really supports 100 kW, then I will admit that it would be very useful for charging relatively small cars, and acceptable for large ones.
Single phase is useless in Europe at power levels above 16 A, because we have no infrastructure for it. We do, however, have infrastructure for the far superior three phase AC. Please take the time to look at the chart at page 13 in the VDE interim report linked to above. They don't even consider single phase at higher power than 16 A, all the rest is DC and three phase AC. They also note that "To enable pure BEVs to travel farther than their battery capacity would normally allow, a significant reduction in charging time is crucial. For this, DC charging is the appropriate way. The DC infrastructure requires much higher investment and will certainly only be available in selected locations, comparable to today's fossil fuel stations." The plan is to use single phase AC at 16 A where nothing else is available, three phase AC everywhere (including at home up to 32 A), and DC quick-charging in selected locations.
Electric power is distributed as three phase power all around the globe, the only difference is whether three phase is run all the way into the homes or stops at the transformer down the road.
Single phase is much harder to convert to DC than three phase. This is just physics. When really large rectifiers are needed, it is not unusual to include a special transformer with two secondary windings feeding the rectifier bridge, one delta wired, the other Y-wired. This converts the three phase to six-phase before rectifying it, because that lowers the overall cost. More phases is better. Look up "rectifier" on Wikipedia. This implies that a high-powered single phase charger is a big, heavy and expensive extra box that is not needed except in the US, the UK and Japan.
In addition, there are articles like this:
Power Politics: Competing Charging Standards Could Threaten Adoption of Electric Vehicles: Scientific American
which suggest that BMW is interested in the SAE DC standard as a universal standard.
Many of us are expecting similar charging times for the 300 mile pack, but even if 45 min applies only to the 160 mile pack, then the required charging time is already beyond 44 kW, so that wouldn't be very future-oriented.
Again, I think 480 V/80 A is a common circuit size in the US. Please correct me if I'm wrong. The exact number is unimportant, the interesting thing is to be able to use as high power as possible for the lowest possible cost. In the US, that might be 480 V/80 A, in Europe, it's 400 V/63 A.
CHAdeMO supports up to 100 kW and SAE (DC) 90 kW. I really don't think Tesla would even want to be the company to try pioneer 3 phase 44 kW ahead of time and on its own.
There really isn't much to pioneer. They've pulled off far more impressive things before, like pushing 900 amps through the motor from a battery than can only deliver 600 amps. That was nifty.
If the situation is as your source suggests, then maybe in 2014-2017 when those things actually start happening, and if european carmakers start announcing specific car models with that feature, Tesla might think about supporting 3-phase 44 kW as a medium-speed charging method as well, in addition to lower-power 3-phase slow/medium charging, and higher-power DC fast-charging.
I recently asked my local electrician what he would charge for a new 32 A three phase circuit with a connector on the outer wall. He wanted NOK 4000 for the job. That equals approximately USD 750. This is now, not the future.
It doesn't really matter when other carmakers announce support for three phase when the infrastructure development so clearly is going in that direction. Waiting would amount to giving away the technological lead.
If Model S does not support three phase, then it will be obsolete before it hits the street. But supporting any charging plug or standard that might come along should not be a problem: The charge port should contain an internal Tesla-specific plug hidden from view, into which is inserted whatever interface the user wants to see. As far as I know, the communication protocol is the same for all the plug types. If different communication protocols exist, then Tesla would just have to interface their way out of that problem too. Tesla does not have to choose what plugs to support, the whole problem can be removed at a relatively modest expense, as long as they support single phase, three phase and DC internally. Of course, it would have been cheaper if there was only one global standard, but that is not the situation.
