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Old 12-17-2016, 01:08 PM   #31 (permalink)
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Originally Posted by ohmman View Post
First, fast charging creates a lot of heat and the battery pack needs cooling.
Heat = wasted energy, no? Which kinda tanks the efficiency of your EV. Also, cooling the battery pack should not, with proper design, necessitate running the A/C to cool the passenger cabin.

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...if you go back to a car that's 120 degrees inside from sitting in the sun, your AC is going to be chugging away for the first 20 minutes or so once you get on the road. That's unnecessary consumption.
Not as much unnecessary consumption as keeping the A/C running for the whole time the car's charging. Of course a roof or other sunshade helps. So does leaving the windows open.

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Old 12-17-2016, 01:45 PM   #32 (permalink)
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Quote:
Originally Posted by oil pan 4 View Post
Where I work we use more power every day than a 2 story 2400sq.ft. house with a family of 5 uses in 12 years.
And they are not shy about spending several million dollars to lower the bills. 3 expansions to conserve natural gas, power but mostly to save water, all no less than 10 million each.
The 700hp ammonia compressor motors draw up to 1,100 amps of 480 on start up and they cycle on and off all the time.
500hp motors draw 500 to 700 amps depending on if they are driving compressors or turbo fans.
We don't use batteries.
Bank maintenance would cost more than it would save.
I work for a NG distribution company where i work directly with meters and consumption data. We have several ethanol producers that use around 400,000 cubic feet of gas per hour, typical house furnaces use 100 cubic feet per hour and run intermittently. A small efficiency increase goes a long way.

If these chargers are going to deliver 350kw, they pretty much have to be installed near hv transmission lines. Even at 7kv street lines it would pull 50 amps if it were a perfect conversion.
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Old 12-17-2016, 02:05 PM   #33 (permalink)
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Then the next question (which I really hope has been addressed) can the current infrastructure handle the increase in demand from widespread adoption of electric vehicles? Particularly, those that want to fast charge everytime they "fill up".

The system is already strained in the late afternoon on hot summer days when people get home and crank their a/c down, now charging their cars at the same time? I think the "connected" car is going to need to be present very early on to know when the system has capacity to charge it's battery.
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Old 12-17-2016, 03:57 PM   #34 (permalink)
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Quote:
Originally Posted by ksa8907 View Post
Then the next question (which I really hope has been addressed) can the current infrastructure handle the increase in demand from widespread adoption of electric vehicles? Particularly, those that want to fast charge everytime they "fill up".

The system is already strained in the late afternoon on hot summer days when people get home and crank their a/c down, now charging their cars at the same time? I think the "connected" car is going to need to be present very early on to know when the system has capacity to charge it's battery.
This is only a problem in places ran by idiots. Idiots who think they are helping the environment by not having enough power generation capacity to meet demand.

On the other hand Texas does not have this problem.
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Old 12-17-2016, 11:01 PM   #35 (permalink)
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The most economical energy storage isn't pumped water; it's an inclined electric railroad. Uphill for storage, downhill for power.

The DIY version might be barbell weights suspended by cables on a flagpole.
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Old 12-17-2016, 11:15 PM   #36 (permalink)
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This 350kW number is fun for them to throw around and get people excited about but no car can use this much charge rate. It would need a 1000v battery to keep the current down to 350 amps. And full liquid cooled contacts and cables. But it will be nice to have charge stations with the massive high kv grid connection and sub station needed to quick charge several cars at the same time at whatever the max rate they can take. I did read an article about the European qick charge start up that is accepting proposals for sites and the main consideration is access to high voltage power lines and easy access to major highway travel. And they all have grid scale Lithium battery storage units to smooth the demand. here is a post from the Leaf forum.
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350kW at 1000V. This was not mentioned. At 400V it is just 140kW. Slightly faster than Supercharger.
BUT that speed is only possible with liquid cooled pins in the plug. Without that extra it is less than 100kW.

1000V packs are big questionmark on small vehicles due to extra complexity.

Also charging at 350kW is not possible due to thermal limitations (car is not capable to extract heat
at that speed from the pack). Imagine at 90% efficiency 35kW of heat. Not going to work.
Even with absurdly massive AC compressor there is not enough surface area for radiators.

I've not even heard of patents about getting heat out of the car.
With my professional opinion, 350kW charging speed is not going to happen with normal cars (at least not within a decade).
I highly doubt 200kW (at least 10 minutes) will work within 5 years.

With buses, semis, ships - definitely possible.

Also another limitation of the lithium chemistry itself. 100kWh battery can do around 120kW (Tesla).
200kWh pack could do around 240kW. But 100kWh pack (no matter the voltage) will not charge at 240kW rate without
MASSIVE improvement. Voltage per cell would tip safe limit instantly.
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Old 12-17-2016, 11:58 PM   #37 (permalink)
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Quote:
Originally Posted by jamesqf View Post
Heat = wasted energy, no? Which kinda tanks the efficiency of your EV. Also, cooling the battery pack should not, with proper design, necessitate running the A/C to cool the passenger cabin.
If you're looking at overall efficiency, yes. Charging more slowly is more efficient from an energy-only perspective. The AC compressor is shared between the battery cooling system and the cabin on my vehicles. That doesn't mean the cabin is being cooled while the battery is cooled. On the contrary, when charging in 110F+ temperatures this summer, cabin cooling was significantly limited when I returned the car. The trade-off here is fast charging = convenience on trips. And having the pack temperature managed is paramount to longevity.

There's also the matter of range. You'd rather pre-cool your cabin on shore power than when you're on pure battery, at least if you've got a long haul ahead of you. That's less important than pre-heating the pack and the cabin, which obviously takes much more energy.

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Originally Posted by jamesqf View Post
Not as much unnecessary consumption as keeping the A/C running for the whole time the car's charging. Of course a roof or other sunshade helps. So does leaving the windows open.
Again, while the cabin fans aren't running and cooling the cabin, the compressor is indeed necessary for pack stability. A shaded spot is much more efficient for the vehicle and the cabin. If it has PV on it, fine. My argument was that the shade is beneficial. Hopefully I've been clearer.
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Old 12-18-2016, 03:11 PM   #38 (permalink)
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Quote:
Originally Posted by sendler View Post
This 350kW number is fun for them to throw around and get people excited about but no car can use this much charge rate. It would need a 1000v battery to keep the current down to 350 amps. And full liquid cooled contacts and cables.
Agreed that none of the present EV's may be able to charge at 350KW.

Fast-charging a 100 KW-H pack in 20 minutes needs 300 KW. But there is a point of diminishing return, just like all engineering. If 200 KW or 250 KW is reasonably priced and does most of what is needed, that's a good place to start. Having the charging standard impose the limits is short-sighted ... and they have all done that at least once already. If we can't get to 350 KW for a while - that's fine by me.

700V for a DC bus voltage is quite common in the US when fed with 480/460V three phase. 1000V DC bus is common in Canada with 600/575V three phase. I don't have experience in Europe, but we have some european equipment that runs up to 690V three phase, so that's over 1000V DC.

My point - these are already common voltages in industry. It will take some engineering to make that safe for vehicles. Again - avoid building the limitations into the charging standard. Aim HIGH. Let the designs strive to reach them.

350A is only 400 HP at 600 VAC. We would normally run parallel 2/0 conductors so that they are easier to handle, but single conductor 500 MCM cable will run 350A 24/7/365, with a 110F ambient temperature. The cables are hard to handle - I would expect an automated system to engage the charger to the vehicle. If you are expecting intermittent use (like a charger does) with temperature monitoring of the conductor a single run of 2/0 is reasonable. But as you mention further down, the connector is the issue.

My point - the cabling is not particularly difficult. A cable-way can take most of the weight, like the monster-sized TV mounts that let you raise/lower/swing the TVs. The difficulty is in the connectors and the user interface. And I'll repeat myself a bit - aim HIGH and let the designs or the materials or the connectors be the limitation - NOT THE STANDARD

Quote:
350kW at 1000V. This was not mentioned. At 400V it is just 140kW. Slightly faster than Supercharger.
BUT that speed is only possible with liquid cooled pins in the plug. Without that extra it is less than 100kW.
I guess that is for smarter people than I to deal with. Maintaining a large enough contact surface to prevent heating while making the connector light enough for a consumer to move around ...

Quote:
1000V packs are big questionmark on small vehicles due to extra complexity.
You have mentioned complexity a few times. There is more insulation at 1000V than there is at 400V. Above 1000V there are corona issues that need to be dealt with. The techs that troubleshoot need better equipment and a bit more training. The contactors and electronics are more expensive. But I'm obviously missing something on the complexity.

Quote:
Also charging at 350kW is not possible due to thermal limitations (car is not capable to extract heat
at that speed from the pack). Imagine at 90% efficiency 35kW of heat. Not going to work.
Even with absurdly massive AC compressor there is not enough surface area for radiators.
I'm not familiar with this issue.

If your battery is charging at 90% efficiency ... it's time to retire it! I would expect 97% would be a bad day. Again - I must be missing something.

Quote:
Also another limitation of the lithium chemistry itself. 100kWh battery can do around 120kW (Tesla).
200kWh pack could do around 240kW. But 100kWh pack (no matter the voltage) will not charge at 240kW rate without
MASSIVE improvement. Voltage per cell would tip safe limit instantly.
This is not consistent with my limited experience. You are listing charge rates just over 1C. NiCd, NiMh, LiFePO4, LiMnO(whatever the Leaf uses), Lithium Polymer ... every rechargeable chemistry I can come up with ... can charge faster than 2C. I must be missing something.
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Old 12-18-2016, 04:08 PM   #39 (permalink)
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The main point is that Tesla is already pushing the limits of charge rate at 120kW for a 400v battery via any reasonable cable/ connector a normal person could be expected to deal with. 1.2C is not too bad on a big Tesla but this would be 2C on a Bolt and 5C on Leaf which would cut the cycle life substantially. The Leaf doesn't even have liquid cooling in the pack and is limited to 50kW/ 2C. These are not hobby batteries with projected cycle lives of 300. I would really hope to get 2000, 80% cycles out of a $100,000 Tesla to 70% capacity.
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800v packs are needed to charge at 300kW such as the upcoming Porsche Mission E but the motor winding insulation and the components in all of the the controllers get excedingly expensive and bulky.
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Old 12-20-2016, 12:10 PM   #40 (permalink)
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VW Group putting the 350kW charging as the strategic basis of its Porsche Mission E. Production by 2019.

Wolgang Hatz, Porsche’s R&D boss, “We don’t do a car because Tesla has done a Model S. We have our own plans. The time was not right before now to bring a pure battery car onto the market. But now the time is right.”

Oliver Blume, Chairman of the Executive Board of Porsche AG on 800v or 400volt 'Porsche Turbo Charging.' “There are two decisive aspects for us: ultra-fast charging and placing the charging stations at the right positions,” “Together, these two factors enable us to travel in an all-electrically powered car as in a conventional combustion engine vehicle. As automobile manufacturer, we actively shape our future, not only by developing all-electrically powered vehicles but by building up the necessary infrastructure as well.”



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