Fast charge batteries for electric cars

[astroron]

Re the discussion of the limitations of electric cars distance traveled
before needing a long time to recharge the battery,it seems
the solution is nigh.
https://scitechdaily.com/breakthrough-enables-full-recharge-of-an-electric-vehicle-in-10-minutes/
Cheers:thumbsup:

[Sunfish]

Very interesting. 60 degrees sounds achievable although I suppose there is an energy cost to speed things up and a general addition heat compared to slow charging. But still cooler than combustion motors.

[AndyG]

Down the track it would seem like a good idea to divert Electric Motor cooling water from the usual external radiator, to the battery box to achieve this. More efficient, considering the heat energy could already be there after a short drive- unless I've missed something?

[ngcles]

Hi Ron,

I applaud this advance and it is good news as a way forward.

One other problem (so far as those living in rural areas is concerned) that also has to be addressed is the fact that the range of electric vehicles is far more limited in highway driving and high-speed cruising, than it is in "city-cycle". Because of the lack of gearing in electric vehicles, they are at their most inefficient when run at high speed almost constantly with few or no brake applications.
The recoup of energy via regenerative braking works well in urban or suburban environments but has virtually no benefit in sustained high-speed cruising and the claimed range decreases significantly. I know my "most used" journey is from my home to Cowra -- 36km (25 minutes), that involves just six brake applications in total and an average speed of 100kmph. Almost no "juice" is saved (or recouped) from regenerative braking there and the range is decreased somewhat.

One reason why electric vehicles work far better in suburban and urban environments than rural areas or highway driving.

Best,

L.

[gary]

Hi Les,

At least in the case of the Tesla's, that has not been true since their
introduction, with highway range at 100km/h being slightly greater
than driving a mixed cycle of slow, medium and high speeds.

For example, see :-
https://www.tesla.com/en_AU/blog/driving-range-model-s-family



From an engineering perspective, that is also incorrect.

In fact they are at their most efficient. :)

Internal combustion engine cars have non-linear power bands.
The amount of torque they can deliver is a function of how
many RPM the motor is spinning at.

There is typically an optimal point where they are rotating at a
specific number of RPM in order to produce the maximum torque.

By comparison, the type of AC motors used in a Tesla have
near constant maximum torque from 0 to about 6000 RPM, while
maximum power occurs at about 10000 RPM long before torque
drops off.

So internal combustion engines are at a distinct disadvantage. They
have to have multi-gear transmissions in order to help flatten out their
power curves.

The transmissions are of course bulky, heavy and expensive and so
it is an advantage if the power plant does not require them.

We engineers would probably refer to gear boxes as a bit of a kludge.
They are a cumbersome attempt to overcome the non-linear power-band
characteristics of the power unit.

Speeding up and slowing down sees energy losses in both internal
combustion engine and electric cars but any car with energy recovery
such as regenerative braking has a range advantage.

If anything, in the case of the Telsa's, given the mixed driving cycle
ranges versus the highway ranges are nearly equal, it probably highlights
more the inefficiencies of internal combustion engine vehicles without
regenerative braking in city cycles.

What is true in all vehicles is that aerodynamic drag goes up with
the square of speed. We all know that from driving long distances that
easing off the accelerator a little can increase the range noticeably.

It also says that anything that can be done to reduce aerodynamic drag
is good.

Without the need for the same levels of cooling that internal combustion
engines require, automotive engineers have the potential to design
vehicles with more streamlined profiles as opposed to the house bricks
most of us drive around in today. :thumbsup:

[ngcles]

Hi Gary & All,

From Tesla:

https://www.tesla.com/en_AU/blog/model-s-efficiency-and-range

See image: More speed = increased electricity consumption leads to decreased range per charge. Little or no braking means the batteries are not being recharged via energy recovery which worsens the "all-round" consumption figure.

Nearly all (if not actually all) internal combustion engined cars with gearboxes use less fuel on highway cycle than they do city. But this is not a direct comparison. My point is that in a rural area and high speed driving, the range of electric vehicles, particularly those with regenerative braking, is less than in the city at lower speeds. Also the energy advantage they have that is recouped from braking is largely lost.

From the graph, fuel consumption is 200W per mile at 60kph and 300W per mile at 100kph -- that's a 50% increase in "fuel" consumption per mile at high speeds over suburban speeds. It doesn't all come down to aerodynamic efficiency. Both petrol and diesel engined cars normally achieve a 15-20% reduction in consumption in highway-type driving over city despite their unsophisticated aerodynamic design. But to emphasise again -- I'm not trying to make a direct comparison electric -v- internal combustion. What I am saying is that for electric, range will still be compromised as average driving speeds increase and the number of regenerative braking events (and the capacity to recoup energy and re-charge the battery) decreases.

I'm not agin electric vehicles. I do believe they have arrived as a niche vehicle for suburban and urban use for many people.

However the range issue, the fact that they are frequently re-charged from electricity produced from fossil fuels, current sticker price and lack of a spare tyre (in some cases) means they are not yet ready to replace all or most internal combustion engined cars -- particularly in rural areas. The number of places at present that service electric vehicles in the city is quite limited and for all intents and purposes does not exist in the bush. Things will likely change in the future, but we're not there yet. I'm perfectly okay with the future and change but they're not there right now for the vast majority of people.

There was an article recently about a 4x4 dual-cab ute electric start-up in the U.S -- the Rivian. Works out the price for such a vehicle imported here now is about $140,000 AUD after import, luxury car tax, exchange rate, shipping and GST. For that amount of money, you could buy two Mitsubishi Triton's and 13,000 litres (about 120,000 kms of driving) of diesel. Or one Triton and 430,000km of diesel. On that basis who would buy a Rivian now?


Best,

L.

[gary]

Hi Les,

Thanks for the response but I see you are confused. :)

The graph shows speed versus energy consumption per mile.

They state :-


In a nutshell the graph shows that the faster you go the more energy you use.

There is nothing new here. We are all familiar with exactly that with
our petrol driven cars. The faster we go, the more fuel we use.

So why do we go faster? To get there quicker! :)

For example, we know if we were to drive from Sydney to the Gold
Coast for a holiday that if we were to drive at an average speed of
100km/h that we will use more petrol than we would if only doing an
average speed of 50km/h.

But we arrive in half the time.

As Tesla says, the drag of a vehicle goes up with the square of the speed.

I know you watch F1. As you are aware, since in-race refuelling is no
longer permitted, you get some drivers conserving petrol by "lifting
and coasting". In order to ensure the range of the car will be enough to
complete all the laps to the end, sometimes drivers are forced to drive
a little slower.

Anyway, so far, so obvious. :)

However ...



No. It means that when driving in stop/go conditions that the range
would be further than it would be if your car did not have an energy
recovery system.

Your logic is back-to-front. :) In a topsy-turvy world where such logic
held true, one would then go further by intermittently braking whilst
driving along the highway, which clearly is a nonsense. :)

I believe one of the sources of your confusion might be where Telsa state :-


They are saying with an electric vehicle you are using less energy
in a city typically because you are driving more slowly. This is also
true of a petrol driven car when it is not stop/start. Then they go onto
say that not only do you conserve energy by driving slowly but that
in stop/go conditions, in addition to that, you have the benefit of
energy recovery.

They are not saying you will get more range by stop/go than you would
compared to just go.

However, the real bottom line is the figures they provide in the first
document I cited.

For example, for their model 85D in the year 2014, it had a quoted range
of 295 miles at 65 mph on a highway and 270 miles in a "EPA 5-cycle
Range" standard, which is a metric of slow, medium and fast driving.

Your final point with regards fitness for purpose across all demographics
as the state of the art of the technology stands today and its level of
deployment, everyone understands.

But for the well-heeled, perhaps retired, country gentleman or lady
who goes from the homestead an hour into town and back now
and then, the choice is there. The decision for people such
as that is not the Tesla versus the Hilux. They are contemplating
the Tesla versus a Porsche Cayenne or possibly even a Ferrari.
They are seeking a little bit of an adrenaline rush cross-multiplied
with some class.

It is early adopters that help drive the price of the technology down.

It was not that long ago that computers costs hundreds of thousands
and millions of dollars.

[gary]

It seems like the Cayenne does have the advantage of being able to do
300km/h on the European autobahns as opposed to the Tesla Model X 's
250km/h.

https://youtu.be/aBOCS0GnWAI

[ngcles]

Hi Gary,



No, I'm not confused, you've got it right and I'd contend you are in furious agreement with me. The faster you go in an electric over a set distance, the more energy you consume.

The reverse applies (up to a point) in a petrol/diesel because they have gearboxes. As you have conceded, an electric uses much more "juice" at highway speed than in suburban/urban speeds. This precisely is my point. However your contention that petrol/diesel vehicles use also use more fuel the faster they go is incorrect.

My 2012 2.5 litre diesel Mitsubishi Triton uses about 10.5 litres per 100km in city driving but that drops to less than 8.5 litres per 100km in the bush. That's an increase in fuel efficiency of about 20%. This is pretty much the same as all petrol/diesel vehicles. The reality is that as engine RPM rises (not speed per se) diesel/petrol fuel consumption increases. But conventional vehicles use gearboxes to they are being propelled quickly for comparatively low RPM.

Again, I'm not here to compare diesel -v- petrol -v- electric. All I am trying to point out, and you have helped prove, is that at highway speeds, the amount of "juice" you use in the Tesla (and nearly all electric vehicles) goes up and range consequently goes down compared to city driving.

Unless you are going to do your highway driving at 60kmh in the Tesla, you are going to use more "juice" on the open road per kilometre than in the city and consequently there is a reduction in range -- possibly up to 50% 60kmh -v- 100kmh.

They seem to have overcome one of the problems with electric vehicles with this new fast-charging tech. But, there are several others that need to be addressed before they can become truly mainstream.

Best,

L.

[Peter Ward]

No.

I never even considered the Porsche. :D

[The_bluester]

Actually I would argue this from the opposite direction. It is not so much that the EV is worse in freeway cruising, it is that they have a big advantage in urban use.

While I believe that the typical EV does trade off a little high speed efficiency for the sake of low speed punch, your Triton will certainly use more fuel the faster you go, aerodynamics mean it is just going to happen, faster = more drag = more engine power required to maintain a speed = more fuel used over a given distance. It is the stop start of urban driving that makes the bigger difference rather than the speed.

Drive from Melbourne to Sydney and back twice, once maintaining whatever minimum speed is required to hold on to top gear (My Navara for instance is a 7 speed auto but does not pick up seventh until 90KMH) and then do it again at 110 and you will measure a clear difference.

The bigger difference is that the EV (And hybrid cars) have a clear advantage in city driving due to the stop start giving them the opportunity to capture energy in regenerative braking that a traditional car can only turn into brake dust, noise and heat. I read recently of a mob developing a two speed transaxle for lower cost EVs to bring motor speeds down into a more efficient range at highway speeds and coincidentally improve their overtaking performance where anything not costing megabucks (Think Nissan Leaf and Hyundai Ioniq) starts to trail off. I am ignoring anything above about 130KMH myself as it is not relevant in the real world of our speed camera infested nation.

[Retrograde]

Speaking of megabucks I noticed that Porsche's new Taycan EV has a two speed transmission to boost performance and range at highway speeds.

[gary]

Hi Paul,

What I believe Les is referring to is that the fuel efficiency versus speed
curves for internal combustion engine vehicles is rarely linear.

A profile often seen is that the economy starts poorly at low
speeds, gets worse as you start to go faster, then at a sweet spot where
you might be cruising in overdrive it can improve and then if you push
it beyond that in speed the efficiency drops off again.

The gears are trying to match the limited optimal spot in the power band.

[The_bluester]

That is a given and the two speed transaxles starting to appear in top line EVs show that they have the same issues with a most efficient engine operating range, but the comparison being made is urban driving versus long distance touring, and that is not really a comparison between speeds but speed patterns. It is highlighting the advantage an EV has over a traditional car in stop start traffic (Energy recovery) which it largely loses as soon as you get away from traffic.


In my case of a 140km round trip commute in mixed conditions it probably still hands the advantage to an EV, it would be nice to know that it could recover energy all the way down mount Pretty Sally in the morning to contribute to going back up it again in the evening.

[gary]

Hi Pete,

Did you see the video of that thing going around the Nürburgring a couple
of months ago? I have a feeling the driver has been around there a few
times before. :lol:

https://youtu.be/8m31EgQkswg

Also check out the Turbo Cayenne doing 300km/h on the autobahn starting
at the 1m55s mark on the previous YouTube link I posted. Don't try this
at home.

https://youtu.be/aBOCS0GnWAI

Having saved up and thinking you had found a prescription for some
mid-life crises, it would be just one's luck if someone then overtook you
on the autobahn in their Porsche 919 Hybrid doing 350km/h :lol:

[Retrograde]

I didn't see it in its entirety - thanks for posting.
It still seems a bit strange not having any engine noise accompanying a performance car but in time I expect we'll re-calibrate our ideas of what a performance car should sound like.



I did about 210km/h on the autobahn last time I was in Germany. It was surprisingly difficult to find the space to do so between traffic, roadworks and the speed-limited zones near large population centres.
300km/h? :eyepop:

[AussieTrooper]

Interestingly, doing a lap of Australia in an EV is starting to get a cult following. There are 'standard' routes being developed, which often divert from the usual highways. This is due to the presence/absence of suitable charging locations.
It's definitely going to start providing an incentive to provide them to ensure customers arrive for motels etc.

[ngcles]

Hi All,

Here is another development which, provided it fulfils its promise might be a game-changer:

https://www.dailymail.co.uk/news/article-7592485/Father-eight-invents-electric-car-battery-drivers-1-500-miles-without-charging-it.html?fbclid=IwAR3GhcBEuN0RwGA6uw S4Tdd7NdTzdRJ49lAOMfOKrz22deLBTBWU0 aAhCrs

Best,

L.

[gary]

Philip E. Ross reports today (https://spectrum.ieee.org/energywise/aerospace/aviation/lithiumsulfur-battery-project-aims-to-double-the-range-of-electric-airplanes) at the Institute of Electrical and Electronics
Engineers (IEEE) Spectrum magazine web site on a company called
Oxis Energy, of Abingdon, UK, who have developed a lithium sulphur
battery that would provide “in excess” of 500 Wh/kg.

They have joined up with a company in Colorado named Bye Aerospace
to have the new battery power an electric plane.




Story here :-
https://spectrum.ieee.org/energywise/aerospace/aviation/lithiumsulfur-battery-project-aims-to-double-the-range-of-electric-airplanes