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Do androids dream of electric cars?

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PDR
1312766.  Thu Feb 07, 2019 4:25 am Reply with quote

Alfred E Neuman wrote:
My personal perspective on electric cars is in a bit of a state of flux.


That would be magnetic cars, surely... :0)

Quote:

To nit-pick, the extra weight does necessarily lead to a drop in range - at steady speed the mass of the vehicle doesnít affect consumption (all else being equal). Accelerating and climbing hills does though, but then regenerative charting will also be increased, so should offset that to an extent.


It's a good quibble, but the weight also incfluences the cornering friction rise (the extra friction due to the lateral forces being generated by the tyres which manifests as an increase in rolling resistance), so unless that drive is in a dead straight line it still has an effect. But the major issue is that the weight of an ICE car drops as you run the tank down, which gives benefits the electrci vehicle doesn't get.

PDR

 
barbados
1312768.  Thu Feb 07, 2019 4:44 am Reply with quote

PDR wrote:


That would be magnetic cars, surely... :0)



Oooo Mag-lev cars - now that would be an advance

 
Alfred E Neuman
1312775.  Thu Feb 07, 2019 7:46 am Reply with quote

PDR wrote:

It's a good quibble, but the weight also incfluences the cornering friction rise (the extra friction due to the lateral forces being generated by the tyres which manifests as an increase in rolling resistance), so unless that drive is in a dead straight line it still has an effect. But the major issue is that the weight of an ICE car drops as you run the tank down, which gives benefits the electrci vehicle doesn't get.

PDR

Agreed, the extra weight does increase consumption, but twenty percent extra weight will cause an increase in consumption of a lot less than twenty percent.

That weight of a tank of petrol (in my car about 45l or 35kg) will not result in a fuel saving that I could accurately measure outside of laboratory conditions. There are far too many other variables which will all have a greater impact on my consumption. Compare that to the batteries in an electric car which weigh around 500kg, a significant weight to drag around all over the place. Of course that is offset by the maybe 100kg* youíll save because the electric motor is lighter than the engine.

* This is a thumbsuck and Iíve only done a very rough mental calculation.

 
cnb
1312777.  Thu Feb 07, 2019 7:52 am Reply with quote

Alfred E Neuman wrote:
But around once a month I drive up to Joíburg and back and do some driving around there, so on any single leg of the trip Iíll be doing up to 700km. When I go on holiday or visit my daughter at university (a few times a year) a single dayís travel is about 800km, often going over 1000km. So Iíd need two cars. An electric for daily use (often around 200-250km a day), and one for road trips. Thatís not going to happen any time soon, because itís just too expensive.


You don't necessarily need to own two cars, you just need to live in a place with good charging infrastructure for your electric car. A friend of mine lives part of the time in south-east England, and part in the French Pyrenees. He makes a return trip approximately monthly, a full day's drive of about 1350km each way, in a Tesla. The extra time taken for charging over filling an ICE car changes it from a 13-14 hour journey to a 14-15 hour one. The only other disadvantage is that his lunch choices are limited to places within walking distance of a Supercharger.

 
PDR
1312780.  Thu Feb 07, 2019 8:19 am Reply with quote

Alfred E Neuman wrote:

Agreed, the extra weight does increase consumption, but twenty percent extra weight will cause an increase in consumption of a lot less than twenty percent.


Oh, I see what you're getting at. yes, I agree that's true.

PDR

 
PDR
1312781.  Thu Feb 07, 2019 8:23 am Reply with quote

cnb wrote:
The only other disadvantage is that his lunch choices are limited to places within walking distance of a Supercharger.


...and you need to time your journey so that the time when it needs recharging is both (a) when you're near a supercharger which no one else is currently using, and (b) a time when you need lunch (or breakfast/dinner/sleep). My prefered way of driving to the south of france, norther italy or most of germany was to drive overnight when the roads are clear. Having to waste an hour or more of that time while the car refuels at a time when I didn't want a meal (I'd had that on the ferry) or a nap (which would make me groggy for the rest of the journey) would be annoying.

PDR

 
Alexander Howard
1312790.  Thu Feb 07, 2019 8:53 am Reply with quote

Tesla coils on the side of the motorway which charge cars as they go along, and invoice the owner at the end of the month.

Or at were called petrol stations you hoick out the discharged cells from your battery and swap them for ready-charged and refurbished cells.

Or just get a hybrid.

I'd suggest hydrogen, but with an overall efficiency of about 2% between power station and engine output, it would need the full output of several village nuclear power stations to keep the gas coming.

 
PDR
1312793.  Thu Feb 07, 2019 9:08 am Reply with quote

Alexander Howard wrote:
Tesla coils on the side of the motorway which charge cars as they go along, and invoice the owner at the end of the month.


Have you any idea of the field strengths required to achieve a viable magnetic circuit over that kind of range? It would not only be hideously inefficient, but it would melt the rest of the car (and anyome in the vicinity) in the process.

Quote:
Or at were called petrol stations you hoick out the discharged cells from your battery and swap them for ready-charged and refurbished cells.


This might be do-able, but the batteries will be big lumps of dangerous stuff, so they need proper mountings and secure fastening. I can't see my daughter manhandling a 200lb lump of sparky stuff as a matter of routine. The electrical connections (and the electrical safety aspects) are also non-trivial problems to resolve before this becomes practicable for untrained users. And then there's the detail that it would require standardised battery packs - same physical configuration, same voltage, same instrumentation, same electrical interface. And personally if I'd just bought a car with a £20,000 battery I ain't going to swap it for some tired old piece of junk at some random roadside garage...

Quote:

Or just get a hybrid.


How about getting a hybrid but without the electrical bits - the same emissions but with lower weight, complexity, cost and failure rate...

Quote:

I'd suggest hydrogen, but with an overall efficiency of about 2% between power station and engine output, it would need the full output of several village nuclear power stations to keep the gas coming.


Depends how you make the hydrogen. I agree that making it electrically from water isn't that efficient, but the biohydrogen concept is a very different prospect. Of all the alternative avenues open to us biohydrogen-fuelled vehicles (whether using fuel cells or ICE, and if it can be made practicable in the required scale) offers the most attractive solution at the moment

PDR

 
Alexander Howard
1312794.  Thu Feb 07, 2019 9:48 am Reply with quote

These were all suggestions I have heard in the aether so I thought I would bring them all together. Thank you for expertly demolishing them! It is rare for engineering practicality to trump vision in discussions of these matters, but the engineers are the ones lumped with trying to bring reality to bear.

 
PDR
1312795.  Thu Feb 07, 2019 10:00 am Reply with quote

Alexander Howard wrote:
It is rare for engineering practicality to trump vision in discussions of these matters, but the engineers are the ones lumped with trying to bring reality to bear.


That's essentially the reason why most engineers are opposed to brexit...

:0)

PDR

[no, I have no idea whether most engineers are opposed to brexit or not - most of the ones I know are, and it happens to suit my argument to assume that they are a representative sample, so that's what I'm going to do!]

 
cnb
1312796.  Thu Feb 07, 2019 10:10 am Reply with quote

PDR wrote:
...and you need to time your journey so that the time when it needs recharging is both (a) when you're near a supercharger which no one else is currently using, and (b) a time when you need lunch (or breakfast/dinner/sleep). My prefered way of driving to the south of france, norther italy or most of germany was to drive overnight when the roads are clear. Having to waste an hour or more of that time while the car refuels at a time when I didn't want a meal (I'd had that on the ferry) or a nap (which would make me groggy for the rest of the journey) would be annoying.


You don't have to charge from empty to full. In fact, it's better if you don't. Sure, if you're going to make a long stop for lunch or a nap it's better if the battery's near empty at that point, but it doesn't make a huge difference.

On a long journey you're presumably stopping for rest/toilet/coffee breaks every two or three hours anyway, and in the middle part of the battery range a current model Tesla car/Supercharger combination will charge at 650-750km/h. As an example, if you have a 100kWh Model S, start an all-motorway (lowest km/kWh) journey with 75% battery, and charge for 15 minutes after each 2.5hrs of driving, the battery will run out at around 1000km. If you make each charging stop 20 minutes, you get past 2000km.

 
dr.bob
1312798.  Thu Feb 07, 2019 10:59 am Reply with quote

PDR wrote:
True enough, although to get a greater range mostly comes from using a bigger battery, and the specific range will then drop due to the greater weight of the larger battery so the gains would not be pro-rata.


Surely a greater range comes from developing battery technology. As an example, the 2012 model of the Renault Zoe was powered by a 22 kWh battery with a weight of 275 kg. Four years later, the new Zoe was launched with a 41 kWh battery. This very-nearly-doubling of energy capacity (and, therefore, range) weighed in at an impressive 300 kg, very nearly the same as the older model. More power, more range, virtually no increase in weight, so your logic above doesn't apply.

PDR wrote:
Also the limiting factor on the recharge time is the capacity of the charger. The standard is currently 100kW for commercial "fast" charging and a bigger battery will take longer to get to the 80% charge point from the same charger.


Two things here. Firstly the 100kW "standard" is Tesla's invention and has been around for a while now. The majority of "traditional" car manufacturers are keen to be able to trump Tesla, which is why they've already standardised on 175kW chargers and some (starting now with Porsche) are intending to develop 350kW chargers.

Secondly, I thought Jenny's initial post was designed to encourage us to think about what the future will bring. There's little point basing an argument on today's technology when that's likely to be superseded in the very near future.

PDR wrote:
And you'd need custom home installations even to use the 100kW charger at a house


Clearly people will not have the same charging facilities in their houses that they do at charging stations, in the same way you cannot fill up a petrol car at someone's house in the same way you can at a filling station.

PDR wrote:
So Jenny* won't be able to do a 1hr recharge at her friend's house unless her friend also has special power provision for an electric fast-charger.


That's true, so unless Jenny's friend lives close to a fast charging station, there are two obvious solution to this problem: Either the range of electric cars becomes good enough that Jenny can make the return trip on a single charge, or the chargers become fast enough that she can pause half way for a minimal amount of time to get a sufficient boost to keep her going.

Given that Jenny has said that her friend lives 130 miles away, my money is on the former. We already have EVs that claim they can do more than 260 miles on a single charge. Clearly these sorts of claims need to be taken with as much of a pinch of salt as ICE vehicles' claims of mpg do, but in a few years time, 260 miles is likely to look as primitive as the 100 mile range of the early Nissan Leafs looks today.

PDR wrote:
I take your point, but if you have a part of your car which costs even £2,000 and has to be replaced every 2-3 years I suspect you' not be happy - I certainly wouldn't!


Where does this "2-3 years" figure come from? It certainly bears no relation to the current reality where manufacturers such as Mercedes are offering an 8 year warranty on their EVs' batteries. To be clear, they confirm that Lithium Ion batteries lose performance over time. However, they guarantee that, if the capacity of the battery drops below 70% at any time in the first 8 years of life, they will replace the battery free of charge.

Also, the cost of replacing batteries is not clear. There is currently a growing market in repurposing old EV batteries. For instance, a UK power company is using them as a kind of "Tesla powerwall" to power your house. This kind of innovation will produce a market for second-hand EV batteries which means that you'd be able to trade in your old battery, not simply have to fork out for the entire cost of a new battery.

Finally, a point I missed earlier. When you said 'I don't know about the E-niro but most of the others like the Nissan Leaf only allow one or two consecutive "fast" charges before you have to do one or more "slow" charges to protect the battery.' it turns out this is not true. Idaho National Laboratory an a test where they compared four Nissan Leafs. Two of them were only charged using slow chargers, and two were only charged using fast chargers. They were all charged and driven twice per day. After over 40,000 miles of travel, they compared the capacity of the batteries. The slow charged vehicles had seen their battery capacity drop by 22.3%, while the fast charged vehicles had experienced a drop of 25.3%. That lead the researchers to conclude that "The impact of quick charging is negligible."

PDR wrote:
Current ICE units last at least 100,000 miles and typically 150-200,000 miles, which amounts to 10-20 years in typical domestic usage. Batteries won't even get close to that


8-10 years is close, no?

PDR wrote:
Elon Musk says all sorts of things - he hasn't delivered on many of them.


But it's not just him. Did you look at the link I provided to the study done by UC Berkeley that said much the same thing?

PDR wrote:
Personally I'd like to see if we can make biohydrogen work before we commit to that sort of thing.


But surely that has its own inherent infrastructure challenges. Plus it's an unproven technology, while EVs are not only tested and proven, but are seeing large-scale uptake in many parts of the world.

 
Alexander Howard
1312800.  Thu Feb 07, 2019 11:24 am Reply with quote

Purely coincidental, I must emphasise - I did not know it was going to be published nor have I ever heard of the writer - but an article urging 'village nuclear' has just appeared on ConHome:

https://www.conservativehome.com/platform/2019/02/stephen-haraldsen-how-smaller-reactors-offer-a-step-forward-for-nuclear-communities.html

 
cnb
1312802.  Thu Feb 07, 2019 12:03 pm Reply with quote

dr.bob wrote:
Where does this "2-3 years" figure come from? It certainly bears no relation to the current reality where manufacturers such as Mercedes are offering an 8 year warranty on their EVs' batteries. To be clear, they confirm that Lithium Ion batteries lose performance over time. However, they guarantee that, if the capacity of the battery drops below 70% at any time in the first 8 years of life, they will replace the battery free of charge.


One of the Tesla owners' forums collected battery capacity and mileage data from a few hundred members. The data was all from cars less than 4 years old, but most Tesla owners drive high mileages.
Their data suggests that for a very high-mileage driver (60,000km/year), you will exceed the average lifetime mileage of an ICE car in Europe (~300,000km) and still have 85-90% of your Tesla's original capacity remaining.
It's less clear what happens over the longer term when the battery is used less (because there's no real data yet), but it looks likely that you'd get to the average lifespan of an ICE car (19 years) with 55-60% of the capacity left.
If those figures are representative then I don't see battery lifespan being a real problem.

Just out of interest, do Mercedes offer the same warranty everywhere? Tesla have a warranty on Model 3 batteries which appears to be the same wordwide (70% after 8 years or 100,000/120,000 miles depending on the exact model). Their Powerwall warranty, however, is 80% after 10 years in cold countries and 70% after 10 years in hot ones.

dr.bob wrote:
Also, the cost of replacing batteries is not clear. There is currently a growing market in repurposing old EV batteries. For instance, a UK power company is using them as a kind of "Tesla powerwall" to power your house. This kind of innovation will produce a market for second-hand EV batteries which means that you'd be able to trade in your old battery, not simply have to fork out for the entire cost of a new battery.


There is clearly a market for used EV batteries. As we move more of our electrical generation capacity to variable sources like wind and solar, there will be a need for lots of energy storage to smooth out that supply. In a static installation energy density and weight are not particularly important, so a battery made of used car cells at 75% of their original capacity but only 50 % of the price will be ideal.

 
suze
1312803.  Thu Feb 07, 2019 12:10 pm Reply with quote

PDR wrote:
Alexander Howard wrote:
Or at were called petrol stations you hoick out the discharged cells from your battery and swap them for ready-charged and refurbished cells.


This might be do-able ... (But) personally if I'd just bought a car with a £20,000 battery I ain't going to swap it for some tired old piece of junk at some random roadside garage.


Alexander's idea was tried in Israel, and the company behind it went bust in fairly short order. That is said to have been down to bad management as much as a bad concept, but the objection which PDR raises absolutely was part of the issue.

See post 1309227, where I talked about some tangents to the discussion which has subsequently been started here.


Alexander Howard wrote:
Purely coincidental, I must emphasise - I did not know it was going to be published nor have I ever heard of the writer - but an article urging 'village nuclear' has just appeared on ConHome:


That writer notes that two under-way projects to build new nuclear power stations have seemingly been abandoned, and a third is only proceeding because a former Chancellor of the Exchequer agreed to pay too much for the electricity that it will produce. This hardly encourages anyone to set about building yet more nuclear power stations. What's more, I rather thought that agreeing to pay too much for the electricity was somewhat at odds with Conservative philosophy. There would be twenty pages of bile in the Daily Mail if a Labour government did it.

It also notes that these new build nuclear power stations were to be built close to existing nuclear power stations. Two plans to build nuclear power stations in locations where there isn't one already were "not shortlisted as deliverable after significant local opposition".

In other words, and as I suggested yesterday, no one wants a nuclear power station in her back yard. There will be "significant local opposition" to any and every proposal to build one in a populated area. The article does not consider how that can be overcome, perhaps because it can't be.

 

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