Wednesday 17th October 2012

Lotus Evora 414E: the tech

A geek's guide to the technology underpinning Lotus's clever range extender Evora, driven recently by PH

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So the Evora 414E we drove delivers a typical Lotus experience, drivetrain notwithstanding. But it's certainly a complex vehicle, the antithesis to the 'add lightness' mantra so often employed by Hethel. So here's your PH guide to how the Evora's plug-in hybrid system functions, and how it could be used elsewhere in the near future.

Evora is a true product of GB PLC

Background
In 2006, the Labour Government created the Technology Strategy Board to boost manufacturing innovation in the UK and fund projects that demonstrated this. The 414E is one of these, part of a joint effort between the TSB, Lotus, Jaguar, Infiniti, Xtrac and Evo Electric. It aims to establish a supply base of EV vehicle components in the UK, with smaller companies such as Evo Electric benefitting from the corporate power of the larger partners whilst imparting their expertise.

Range-extender engine
The 414E is different to the Vauxhall Ampera  and Toyota Prius Plug-In as its internal combustion engine was designed specifically as a range-extender only, as opposed to borrowing a conventional engine. This means it can be optimised to work only at the speed required to power the generator (3,500rpm), making it more efficient. The Lotus range-extender is a 1.2-litre three-cylinder with 48hp and tri-fuel (petrol, methanol and ethanol) capability. It utilises Lotus's new mono block design, incorporating the block, head and exhaust manifold into one unit. This makes it lighter (51kg) and smaller, which is crucial when you see it crammed in amongst the elctronics in the back of an Evora.

Packaging the tech is no easy task

The Evora's range-extender (a prototype whose construction differs slightly from the production version) is modular, which allows parts to be added or taken away without significant internal modifications. Already a supercharged version with 68hp exists for higher-performance installations, whilst a two-cylinder also exists to be used where space is at a premium.

Battery pack
Sitting in place of the rear seats in the Evora 414E, the battery pack weighs 250kg and is rated at 14.9kWh. It comprises 1,780 lithium ion battery cells. Predictably, the charging of these batteries produces a huge amount of heat so there are four cooling pumps to ensure they remain at optimum temperature. A lot of time was invested in a battery management system to support the cooling and also ensure recharging takes place at the correct time.

At present, the range-extender will automatically assist the batteries when they have around 35 per cent charge level remaining. At 100 per cent, the EV range is 30 miles, whilst draining it and the 30-litre fuel tank of the range-extender gives a total range figure somewhere near 300 miles. CO2 emissions are rated at 55g/km

Lotus's range-extender motor promises much

Generator
The generator comes from British firm Evo Electric. It is driven straight off the crank of the range-extender, which saves on weight and cost.

Electric motors
Two synchronous axial flux drive motors also from Evo Electric power the Evora 414E, delivering 207hp and 369lb ft each. They are charged through four inverters (which are the four silver rectangular boxes in the images) and channel power to the road through an Xtrac single-speed transmission. Lotus has invested heavily in ensuring accurate torque distribution between each wheel, meaning that torque vectoring will feature in future developments of the 414E.

[pimpchez]

Impressive tech and packaging .But the battery only range is piss poor comapred to a tesla ,well there claimed figures anyway .

i think they should be investing more in innovative new batteries ,that last long and charge quicker
















edit : woo 1st time top poster

[kambites]

pimpchez said:

Impressive tech and packaging .But the battery only range is piss poor comapred to a tesla ,well there claimed figures anyway .

That's a completely different type of car though - the Tesla is electric, this is primarily a petrol powered car.

[LordFlathead]

kambites said:

That's a completely different type of car though - the Tesla is electric, this is primarily a petrol powered car.

No it's not, it's an electric car with a range extender (petrol) engine which is designed to charge the batteries not power the car directly.

[kambites]

LordFlathead said:

kambites said:

That's a completely different type of car though - the Tesla is electric, this is primarily a petrol powered car.

No it's not, it's an electric car with a range extender (petrol) engine which is designed to charge the batteries not power the car directly.

Yup, and to my mind that makes it primarily a petrol powered car. You could run a car like this quite happily without ever plugging it in, and I'm sure when they become widely available lots of people will. I don't really see that increasing the electric only range would benefit it significantly. The batteries are just being used as a buffer to allow the petrol engine to run at optimal efficiency all the time that it's active.

I think 30 miles is enough to cover most commutes, anyway.

ETA: According to the government, the average commute length in the UK is 8.5 miles each way, so 30 mile electric-only range seems pretty well judged.

Edited by kambites on Wednesday 17th October 14:24

[pimpchez]

kambites said:

LordFlathead said:

kambites said:

That's a completely different type of car though - the Tesla is electric, this is primarily a petrol powered car.

No it's not, it's an electric car with a range extender (petrol) engine which is designed to charge the batteries not power the car directly.

Yup, and to my mind that makes it primarily a petrol powered car. You could run a car like this quite happily without ever plugging it in, and I'm sure when they become widely available lots of people will. I don't really see that increasing the electric only range would benefit it significantly. The batteries are just being used as a buffer to allow the petrol engine to run at optimal efficiency all the time that it's active.

i dont think it matters how u define it per say .

At the end of the day it has a mode that lets the car run of batteries "ONLY".Yes i know the tesla is battery only so would have more space for added capacity ,but the evoras range is still **** ,one lap around any major city in the country and that engine is firing back up.

thats why i say ,look at improving battery technology and go into the smaller suppliers.

[kambites]

It's a bit of a shame that they've had to sacrifice the boot, though. That doesn't bode especially well for squeezing the system into smaller, more mainstream cars.

[kambites]

pimpchez said:

i dont think it matters how u define it per say .

At the end of the day it has a mode that lets the car run of batteries "ONLY".Yes i know the tesla is battery only so would have more space for added capacity ,but the evoras range is still **** ,one lap around any major city in the country and that engine is firing back up.

thats why i say ,look at improving battery technology and go into the smaller suppliers.

Oh I agree it's not exactly pushing the boundaries of battery technology, I just don't think it needs to. I see no problem with the engine firing up if your'e driving over 30 miles. More batteries would make it (considerably) heavier than its already rather hefty kerb weight and for what benefit?

I guess there's no fundamental reason they shouldn't offer cars with various different sized battery packs.

Edited by kambites on Wednesday 17th October 14:30

[stolenink]

kambites said:

LordFlathead said:

kambites said:

That's a completely different type of car though - the Tesla is electric, this is primarily a petrol powered car.

No it's not, it's an electric car with a range extender (petrol) engine which is designed to charge the batteries not power the car directly.

Yup, and to my mind that makes it primarily a petrol powered car. You could run a car like this quite happily without ever plugging it in, and I'm sure when they become widely available lots of people will. I don't really see that increasing the electric only range would benefit it significantly. The batteries are just being used as a buffer to allow the petrol engine to run at optimal efficiency all the time that it's active.

I think 30 miles is enough to cover most commutes, anyway.

ETA: According to the government, the average commute length in the UK is 8.5 miles each way, so 30 mile electric-only range seems pretty well judged.

Edited by kambites on Wednesday 17th October 14:24

Absolutely agree. This has to the future. There is no where near enough central electrical infrastructure to support plug in cars and that idea should have been blocked by central government loooong ago (and saved us the pain of the Gee-Wazz abonimation). Fossil fuel alone has a short life span of maybe a generation (resource reserve arguments to one side for a mo), but this has the best of both worlds in a single glorious package. Just need to sort the p1ss-poor energy/mass battery bit. Fair play to GB Plc I say - we've still got the engineering potential to rival the world IMHO.

[suffolk009]

Brilliant that they've built this. A crying shame that batteries are still so big - do they BTW have a better shelf life than the ones in my laptop, they seem to only be any use for a year or two.

It makes sense as a project, 30miles to cover the commute/run to teh shop or school run, the range extender is there to let you get to LeMans in a normal manner.

I know there are all sorts of issues about the cost of electricity and how you make it, but this type of package isn't going to go away. Nice to see the Lotus name on it.

[kambites]

suffolk009 said:

Brilliant that they've built this. A crying shame that batteries are still so big - do they BTW have a better shelf life than the ones in my laptop, they seem to only be any use for a year or two.

Yes, the batteries should last much longer in a range extender car than in almost any other application because it's one of few situations where the battery management system has complete control over the recharge cycle of the batteries (since it always has energy on demand).

I think the batteries in a system like this should easily out-last the rest of the car. I suppose extremes of temperature might still hurt them.

[kambites]

I suppose the batteries might still fail if left for months on end unused, too.

[f1ten]

the batteries are very heavy. this technology is a long way off making it an interesting alternative. i hate to think how many hours and miles those batteries will last before they need to be replaced... 5 years??? and then the cost of new batteries?!

[kambites]

f1ten said:

i hate to think how many hours and miles those batteries will last before they need to be replaced... 5 years??? and then the cost of new batteries?!

Nope. They should comfortably out-last the rest of the car.

Li-ions have pretty much an infinite life-span if treated properly. Certainly well into the tens of years as long as they aren't allowed to get too hot or left to discharge for months on end.

Edited by kambites on Wednesday 17th October 14:51

[zebedee]

30 litres of fuel and 300 miles - how many mpg is that?

And how much would it cost in electricity to charge the batteries for the first 30 miles?

Or put another way, 270 miles for 30 litres of fuel - how many mpg is that?

[Alfanatic]

LordFlathead said:

kambites said:

That's a completely different type of car though - the Tesla is electric, this is primarily a petrol powered car.

No it's not, it's an electric car with a range extender (petrol) engine which is designed to charge the batteries not power the car directly.

It's range is 300 miles, I don't see any reason to ignore the 270 miles that you can get when using the complete power unit, not just the electric element. If you wanted an electric only car then better to chuck the combustion engine out and fill that space with more batteries instead. As it is, you get 300 miles and you don't need to plug it in overnight, which to my mind beats the Tesla hands down for practicality, but loses heavily (I would guess) on miles per £ of energy.

Still, it's closer to a Prius than a Tesla IMO, i.e. it's a hybrid, but turned around so that the electric motor is the primary motivator, not the combustion engine, and that gives it much better efficiency than the Prius (which I believe can only manage a fraction of the distance on battery power alone). So it gives you the range and practicality of a Prius but with better efficiency, and the power and torque delivery of the Tesla but with better range and practicality.

Even if you turn that on its head and say it's not as efficient as a Tesla, it still stands that this power unit seems to be a better way of doing hybrid than the Prius solution, with no relative drawbacks. So it trades punches with the Tesla but seems to win across the board against the Prius, powerplant wise at least.

[kambites]

zebedee said:

Or put another way, 270 miles for 30 litres of fuel - how many mpg is that?

41mpg on petrol alone.

[ugg10]

Nice one Lotus, loads of innovation on show here -

Love the idea of an engine that has no head gasket to blow, great for turbo/supercharging opportunites, casting and machining this must have been a real challenge.

IMHO Rnage extenders are the way to go in the near/medium term. These work well for most situation when prolonged hard acceleration is not required (i.e. everyday motoring, sorry not very PH but a reality on today's conjested roads). The idea of a constant speed, ultra efficient petrol or diesel generator providing energy through a battery or capacitor buffer to electric motors makes sense.

In simplistic terms, if you draw a graph of power vs time for any journey the area under of the graph is the fuel required and this dividied by the time is the average power needed to complete the journey. If the buffer can then provide extra power for the spikes and regen breaking and the generator can fill in the dips in the graph you have a very efficient system.

I'd be interested to see this system with 2x100HP motors, capacitors rather than batteries in a small, lightweight car which should be very efficient and still pretty good to drive. Aim - car under 1250kg (being realistic), fiesta or S2000 size/shape, 200 HP, 300 ft lbs, 50+ mile range and 100 miles/gallon on a 100 mile journey of mixed real world driving (i.e. my commute !!!)and the same price as a mid range similar car (not the silly price that the Ampere is going for compared to a mid range Insignia, £37k vs £22k)

Out of interest, does anyone know whether this engine also has the electric valve actuation on it that Lotus were playing around with on the Rover K series a while back (I suspect not but would be intersting to see)?

Edited by ugg10 on Wednesday 17th October 15:21

[Alfanatic]

zebedee said:

30 litres of fuel and 300 miles - how many mpg is that?

And how much would it cost in electricity to charge the batteries for the first 30 miles?

Or put another way, 270 miles for 30 litres of fuel - how many mpg is that?

40.91 according to this site:

http://www.mpg-calculator.co.uk/

[kambites]

ugg10 said:

Out of interest, does anyone know whether this engine also has the electric valve actuation on it that Lotus were playing around with on the Rover K series a while back (I suspect not but would be intersting to see)?

Would it give any benefit on this engine, since it only ever runs at one speed and under one load?

[crofty1984]

ugg10 said:

Nice one Lotus, loads of innovation on show here -

Love the idea of an engine that has no head gasket to blow, great for turbo/supercharging opportunites, casting and machining this must have been a real challenge.

I had a play with a range extender block once, you could easily pick it up with 1 hand, sit it on your knee, etc.
This kind of tech is the way for electric cars really. At least until you can charge a battery to 300 miles range in 5 mins (comparable to filling up a normal car with petrol).