Jaguar I-Pace

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Col Lamb
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Post by Col Lamb »

Range is a concern.

Not specifically for daily around town or shortish journeys.

If we had an EV like the iPace with its limited range then as my Wife and I go into the Lake District or Yorkshire Dales from home for the day fairly regularly we can easily rack up 200 miles so yes range is an issue but it will only be an issue if we cannot get some form of booster charge whilst we are out.

We are shortly going to the NEC which is 115 miles each way at 70 mph for 110 of the 115 miles. We would do the 115 miles in one go and as long as charging at the NEC is available then we can get home without having to find a rapid charge point at a dealer or on the motorway.

W/mile is all well and good but I am more interested in range at a series of constant speeds, 50/60/70 etc that would be for more usefull in giving a ball park estimate of how far you could plan on driving before a boost charge was required, and then mire figures on how far you could travel on at the constand speeds before another boost charge was required.
Col
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Macananon
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Post by Macananon »

Only place to charge at NEC is in resort world car park. And that will cost you £15 for more than 2 hrs.
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Post by Deleted User 1874 »

Col Lamb wrote: Wed Oct 10, 2018 12:36 pm W/mile is all well and good but I am more interested in range at a series of constant speeds, 50/60/70 etc that would be for more usefull in giving a ball park estimate of how far you could plan on driving before a boost charge was required, and then mire figures on how far you could travel on at the constand speeds before another boost charge was required.
Plenty of real world data out there now. Sweet spot for speed vs overall trip time is already well above legal motorway speeds for large battery EVs. I usually cruise along at a leisurely indicated 75 mph on long haul, but mainly so I don't have to pay much attention to speed traps. Gone are the days of ton plus motorway cruising in the UK. You'd lose your license in no time these days with big brother looking everywhere.
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Post by Deleted User 1874 »

Macananon wrote: Wed Oct 10, 2018 10:48 am the elephant in the room is still range, especially at motorway speed of 70-80.
This was the whole point of the Tesla Supercharger network, so rapid charge times allow a 70-80 mph cruise without losing time overall due to long charging stops. The public charging infrastructure has not yet caught up with the Tesla standard, but surely will in the next few years. The reality is that range is less of an issue than most people believe it is.
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Post by Macananon »

The point of my post is that it would be better to concentrate on range and not speed, hence my comment on gearing. If the cat goes further for the same amount of charging that surely has to be good for the environment and the owner.
johnd
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Post by johnd »

Macananon wrote: Wed Oct 10, 2018 2:56 pm The point of my post is that it would be better to concentrate on range and not speed, hence my comment on gearing. If the cat goes further for the same amount of charging that surely has to be good for the environment and the owner.
Still don't really understand the argument. I would say:

1. I'm no engineer, but it doesn't appear that the efficiency of the electric motor changes materially over its normal operating rpm range. So gearing won't help efficiency. It simply takes a defined amount of energy to sustain the car at a certain speed and that energy is not related to the rpm of the electric motor, to a first approximation at least, it's mostly down to aerodynamics and (presumably) frictional losses in the drive train, tyres etc.

2, If you're concerned about extra energy being used during acceleration then limit the energy supplied electrically. Everything is there already to do this without extra mechanical weight/complexity.

3. There is already a trade-off between speed and range. IF you want more range then drive more slowly - it certainly makes a material difference to drive at eg low 70's rather than low 80's say for motorway driving.
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Col Lamb
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Post by Col Lamb »

Macananon wrote: Wed Oct 10, 2018 2:56 pm The point of my post is that it would be better to concentrate on range and not speed, hence my comment on gearing. If the cat goes further for the same amount of charging that surely has to be good for the environment and the owner.
Whilst the idea is sound the realities will be a bit different.

Weight increase will be a fair few additional kgs but the complexity of integrating a gearbox with each electric motor unit will be a major Engineering task. Do remember that EVs do have more than on electric motor with the iPace having two whilst other EVs can have three or four motors.

Additionally transmission losses between the engine and wheels in an ICE account for up to 10% of the engines power and translate this into an EV which has gearboxes and that would equate to even less W/mile and hence reduced range.

The electrical controls of an EV is a very sophisticated system, it has to be for if it is inefficient then the dreaded W/mile and hence range will suffer. The electric motors used in an EV are state of the art units that are Engineered to minimise the current flow required to initiate rotation and hence forward motion in the EV, current flow generates heat which is the enemy of electrical systems since heat directly affects efficiency.
Col
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Macananon
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Post by Macananon »

Deleted User 1874

Post by Deleted User 1874 »

Macananon wrote: Wed Oct 10, 2018 2:56 pm The point of my post is that it would be better to concentrate on range and not speed, hence my comment on gearing. If the cat goes further for the same amount of charging that surely has to be good for the environment and the owner.
They do already concentrate on maximising range. Adding a gearbox would not be of any benefit given the operating speed range of these motors. That's why they don't generally have or need multiple gears. The engineers have certainly given it more thought than you or I! The first Tesla Roadster was tested with a dual speed gearbox, but they soon ditched the idea and it never made it into production.

The real key to efficiency is aerodynamics, which Jaguar appear to have compromised on to some extent. The styling trend of ever bigger wheels and ultra-low profile tyres is also proving to be a significant issue for EV range. I predict we will see a move back to more practical rim sizes and tyre profiles, which the chassis engineers will be thankful for too! These things were always an issue for ICE range/efficiency too, but nobody really gave a monkeys simply because range was not a limiting factor. Now that range is a critical parameter with EVs, this will drive the efficiency benchmarks forward. A Tesla Model S has a Cd of only 0.24 and the Model 3 is down to 0.23. These are way below the industry norm.
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VanB
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Post by VanB »

Interesting figures, Peteski as I think most "aerodynamic" cars fall in the 0.3-0.32 cd range so 0.24 and 0.23 cd is very impressive
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