“and claims a charging rate of up to 11 kW and with an efficiency of about 90% for easy overnight charging.”
That’s a some 9kW lost on a 80kW battery. I get the convenience, but I think the best use for those would be when standardized and installed in public parking spots, for a brief charge bump, not to charge fully at home, e.g overnight, which is what Porsche aims for.
The 90% efficiency of the wireless transmission would be on top of the efficiency of typical charging (which is mostly losses after the power reaches the vehicle).
Do we? Because if you're invoking scare quotes, I don't think you have a good grasp on what's actually happening here.
90% is pretty good efficiency at this level of power. One cannot give an exact figure because it depends heavily on environmental factors, primarily temperature. 90% is pretty much exactly what I'd expect to see in the real world under same conditions.
>One cannot give an exact figure because it depends heavily on environmental factors
Right there. You've restated the problem. "up to 90%" is nothing guaranteed. If the suspension does not lower, you're not getting 90%. If the charger is covered in dirt, you're not getting 90%. If nothing is guaranteed, I'm scared to volunteer.
Well at least doesn’t have to worry about “suspension does not lower” and “charger covered in dirt “ or “cat hides under there for warmth” problems. Those are on top of the existing charging losses.
Heh. I didn't mean it in a gruesome way :-) just saw that someone mentioned it has a sensor to shut it off. So assuming it works as designed a cat might like the nice warm pad to hang out on in the winter. Owner parks hoping to charge their car by morning, the pad charges for 10 min, stray cat notices car is back and hides in there for warmth, charger stop charging immediately, cat moves on, and next day the car is not charged and the owner can't leave for work. It's just not a failure mode a cable has to worry about.
Porsche is famous for underpromising and overdelivering.
For instance they claim a 0-60 time of 2.4s for this car. Car & Driver independently tested it and achieved 2.1s. They also claim 298 miles of EPA range (mixed highway & city driving). Car & Driver worked out 300 miles at a constant 75 mph (which is harder on an EV than city driving.) On the base model, which claims 303 miles range, MotorTrend achieved 350 miles of pure highway driving.
Pick any Porsche and you'll see that they lie to make things sound worse than they really are.
Yeah, the difference between "reported and delivered" in the range of 350-298=62miles is actually that one special thing, that makes Porsches worth the price :-D
German brands in general tend to do that - BMW is notorious for under-reporting power, for example. They'd rather understate than have customers be mad at them for underdelivering.
"This may sound like one of those overly pedantic fixations... but it's not. Power and energy are very different concepts." -Technology Connections
Charging rate of 11 kW, with efficiency of about 90%, means that the charger sucks around 12.2 kW of power from the grid, of which 1.2 kW is continually lost*, and only 11 kW is effectively being stored in the battery at any point in time.
I don't understand the mention about battery capacity (80 kWh, which would translate to around 7½ hours of charging at 11 kW, if a battery could charge at a uniform rate) or where the "9 kW lost" figure comes from.
*Which is probably useful to melt snow above the device, when installed outdoors on cold climates.
The Cayenne seems to need about 315Wh / mile. I assume a substantial number of them are sold in California, where rates are often above $0.50/kw. I think $1.50 would get you about 9 miles.
I drive a more efficient PHEV and spend much more than $1.50/day.
Average cost of electricity is around 18¢/kWh. $2 of electricity at 18¢/kWh is about 11kWh. 11000 / 315 = 34.9. The average US driver does about 40 miles of driving a day. Its a pretty close gut-estimate figure to a median US driver paying an average price per kWh with this particular car.
> I drive a more efficient PHEV and spend much more than $1.50/day.
Cool story bro. I drive a more efficient EV and spend less than $1.50/day. Isn't it fun to share anecdotes?
I keep wondering why a robot-vacuum-charging-dock style solution hasn't materialized. We've seen to robotic arm demos but those aren't around because they are overkill for the task. But something that the car autonomously and accurately docks into and attaches from either the front fascia or underneath. Same charging standard but with a more forgiving connector design that guides and locks in.
Probably because it requires working connectors and humans driving into the exact centimeter correct parking position each and every day, no matter if in a hurry or at night or in snow with impaired vision.
There were rumors flying that WiTricity had a deal to provide wireless charging for Kia and Hyundai’s joint EV power train project.
They were claiming that they’d gotten the losses down to 2x the wall to battery losses of wired chargers, by removing the transformer in the charger and handling the voltage conversion in the coils.
Also you’re prematurely optimizing. By comparing wireless charging to wired instead wireless to internal combustion. If we did things your way it would reduce the rate of electrification of the market. So calm down.
The way my house is set up I can only get power from the passenger side of my car and almost twenty feet away. There’s no EV I’m interested in that can b charged from that side. They tend to put them on the driver’s side to keep you from driving off while still plugged in. Wireless has no plugin. Which would also simplify public charging stations.
Those public chargers are likely to see much higher utilization than in-home ones. If your concern is wasted energy, time an individual vehicle spends charging seems like the wrong metric.
cromka · · focus · HN ↗
That’s a some 9kW lost on a 80kW battery. I get the convenience, but I think the best use for those would be when standardized and installed in public parking spots, for a brief charge bump, not to charge fully at home, e.g overnight, which is what Porsche aims for.
cisc · · focus · HN ↗
It's about the same as wired AC charging. There are always charging losses:
<a href="https://insideevs.com/features/711659/ev-charger-efficiency-losses/" rel="nofollow">https://insideevs.com/features/711659/ev-charger-efficiency-...
onetwentythree · · focus · HN ↗
cisc · · focus · HN ↗
1970-01-01 · · focus · HN ↗
It is "up to 90%"
We all know what this means in reality.
unrented7977 · · focus · HN ↗
90% is pretty good efficiency at this level of power. One cannot give an exact figure because it depends heavily on environmental factors, primarily temperature. 90% is pretty much exactly what I'd expect to see in the real world under same conditions.
1970-01-01 · · focus · HN ↗
Right there. You've restated the problem. "up to 90%" is nothing guaranteed. If the suspension does not lower, you're not getting 90%. If the charger is covered in dirt, you're not getting 90%. If nothing is guaranteed, I'm scared to volunteer.
blackoil · · focus · HN ↗
rdtsc · · focus · HN ↗
phoronixrly · · focus · HN ↗
drcongo · · focus · HN ↗
DANmode · · focus · HN ↗
If a pet, person, or metal object gets between the pads, the system supposedly stops working so nothing overheats.
So, it might get a cat yelled at ^_^
rdtsc · · focus · HN ↗
crote · · focus · HN ↗
DANmode · · focus · HN ↗
Then you don’t, unfortunately.
> 90% is pretty good efficiency at this level of power
Too good. That’s what they’re saying.
randerson · · focus · HN ↗
For instance they claim a 0-60 time of 2.4s for this car. Car & Driver independently tested it and achieved 2.1s. They also claim 298 miles of EPA range (mixed highway & city driving). Car & Driver worked out 300 miles at a constant 75 mph (which is harder on an EV than city driving.) On the base model, which claims 303 miles range, MotorTrend achieved 350 miles of pure highway driving.
Pick any Porsche and you'll see that they lie to make things sound worse than they really are.
KellyCriterion · · focus · HN ↗
piperswe · · focus · HN ↗
joinHNtheysaid · · focus · HN ↗
[dead]
beAbU · · focus · HN ↗
*kWh
Using the right units is important.
cheschire · · focus · HN ↗
<a href="https://www.youtube.com/watch?v=OOK5xkFijPc" rel="nofollow">https://www.youtube.com/watch?v=OOK5xkFijPc
yunnpp · · focus · HN ↗
tommica · · focus · HN ↗
helsinkiandrew · · focus · HN ↗
Wouldn't an overnight (usually cheaper) 10+ hour charge be a great use for (slow) 11 kW charging?
PetitPrince · · focus · HN ↗
solarkraft · · focus · HN ↗
(Some of this becomes clearer when you have a feeling for the units: kW is a measurement of power, not energy)
Rygian · · focus · HN ↗
I don't understand the mention about battery capacity (80 kWh, which would translate to around 7½ hours of charging at 11 kW, if a battery could charge at a uniform rate) or where the "9 kW lost" figure comes from.
*Which is probably useful to melt snow above the device, when installed outdoors on cold climates.
idiotsecant · · focus · HN ↗
onlyrealcuzzo · · focus · HN ↗
This would cost $0.15 to $0.20 per average trip to NOT plug in.
Average person spending $100k on a car would likely pay that without a second thought.
scottm01 · · focus · HN ↗
I drive a more efficient PHEV and spend much more than $1.50/day.
vel0city · · focus · HN ↗
> I drive a more efficient PHEV and spend much more than $1.50/day.
Cool story bro. I drive a more efficient EV and spend less than $1.50/day. Isn't it fun to share anecdotes?
xyst · · focus · HN ↗
DANmode · · focus · HN ↗
Seemingly not.
[deleted] · · focus · HN ↗
[deleted]
pyaamb · · focus · HN ↗
sodastar · · focus · HN ↗
MisterKent · · focus · HN ↗
namibj · · focus · HN ↗
ramses0 · · focus · HN ↗
...obviously never productionized.
[deleted] · · focus · HN ↗
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hinkley · · focus · HN ↗
They were claiming that they’d gotten the losses down to 2x the wall to battery losses of wired chargers, by removing the transformer in the charger and handling the voltage conversion in the coils.
Also you’re prematurely optimizing. By comparing wireless charging to wired instead wireless to internal combustion. If we did things your way it would reduce the rate of electrification of the market. So calm down.
The way my house is set up I can only get power from the passenger side of my car and almost twenty feet away. There’s no EV I’m interested in that can b charged from that side. They tend to put them on the driver’s side to keep you from driving off while still plugged in. Wireless has no plugin. Which would also simplify public charging stations.
sagarm · · focus · HN ↗