Tesla Model S Vs Sunswift eVe.. 500 km range on 1/5 the battery capacity

Recently EV News had the opportunity to test drive two electric vehicles with 500 km range within a fortnight of each other. One, a Tesla Model S P85+ and the other a world record breaking electric car, the University of New South Wales Sunswift eVe solar race car.

I wrote last year how in many ways the two share a common heritage with technology in the Tesla having a direct evolutionary path from the inaugural World Solar Challenge in 1987. While I was massively impressed by my short drive in the top-of-the-line Model S, it's interesting to analyse the strengths and weaknesses of two EVs that both achieve the holy grail of plug-in vehicles, 500 km range on a single charge.

Following Sunswift eVe's World Record run in July, Wired magazine hailed the student-run university project as Tesla's new competitor, ahead of the likes of BMW or General Motors. Hyperbole? Perhaps as eVe is not a road registered vehicle let alone production ready. But that doesn't detract from the fact that during the world record run, Sunswift eVe achieved 500 km range at highway speeds of 107 km/h (66 mph), sans solar array charging, with a battery pack made of the exact same Panasonic cells used by Tesla but with 1/5 th the capacity of the Model S.

It should also be noted that the Tesla Model S maximum range of 502 km is set under the NEDC (New European Driving Cycle) test procedure. Tesla motors themselves claim a maximum range of 480 km at a steady 88 km/h (55 mph) while the official EPA rating is 426 km.

Taking into consideration that much of the Model S design, from the large wheelbase to the all aluminium body construction, is dictated by the 500 km range goal and the size and weight of the battery pack required to achieve that, any vehicle that achieves energy efficiency sufficient to reduce the 18650 battery cell count from 7,104 to 1,200 must offer some advantages.

Number one on the list is direct drive in-wheel motors. Sunswift eVe is rear wheel drive powered by 2x 1.8 Kw (10 Kw Peak) Australian developed direct drive CSIRO wheel motors that give eVe a top speed of 140 km/h. The axial flux BLDC wheel motors are 98.3% energy efficient and because the wheel rim is bolted directly to the permanent magnet rotor, there are no gearing losses which typically reduce energy efficiency at the tires by 20-30%.

Sure, rated power of only 1.8 kw is barely enough to run a 4 slice toaster but the driving experience demonstrated that 20 kw peak (27 horsepower) provides enough performance to accelerate and maintain highway speeds with minimal fuss. Each wheel motor weighs in at only 15 kg with the 99.2% efficient motor inverters adding less than 1 kg each to over-all powertrain weight.

Next up is aero efficiency. Because the car was deigned for a 3,000 km race with a high average speed on extremely limited solar power, aerodynamic efficiency is king. Sunswift eVe has a 1800 x 4500 mm footprint (larger than a Tesla Roadster) and although the car has twice the frontal area of its blade-like solar car predecessor, Sunswift has achieved a similar drag coefficient. It’s managed this partly through a unique high-set “tunnel” underside design, giving the car the look of a catamaran.

Where the Tesla Model S 0.24 drag coefficient is the lowest of any production vehicle, Sunswift eVe, designed exclusively using Computational Fluid Dynamics (CFD), achieves a Cd less than half that of a Tesla Roadster. During my test drive of eVe, even though the vehicle had both doors removed for easy access, the lack of aero drag seemed noticeable while coasting. One team member told me it takes eVe several kilometers to coast to a stop from 100 km/h.

While the Model S monocoque is entirely aluminium, every panel on the Tesla Roadster was carbon fibre and UNSW has taken that a step further and fabricated the entire chassis from the material. Manufactured through a sponsorship deal with New Zealand firm Core Builders Composites, the company that built much of the America's Cup fleet, the vehicle has a kerb weigh of just 320 kg. A Tesla Model S weighs 2100 kg.

The main benefit of light weight when at constant speed is reduced rolling resistance. Approximately 5–15% of the fuel consumed by a typical car may be used to overcome rolling resistance. Sunswift eVe uses Michelin special order low rolling resistance tyres which are run at 80 psi. While not exactly the same kind of road car tires as the 285/30 R21 at the rear of a P85+, they are possibly not too far removed from the bicycle like 155/70 R19 tires fitted to the BMW i3.

The combination of zero mechanical transmission losses, high electrical energy efficiency, low aero drag and rolling resistance means a 16 kWh battery made from 1200x Panasonic NCR18650 cylindrical Lithium Ion cells with a pack weight of only 63 Kg is enough to give eVe a single charge highway speed cruising range of over 500 km. That's the same battery capacity as a Mitsubishi iMiEV which has a maximum range of 155 km or a Volt which achieves 70 - 80 Km in EV mode.

Although carbon fiber is roughly 20 times more expensive than steel, BMW believe it is the future of electric vehicle production and have invested €400 million to launch the first carbon fibre reinforced plastic (CFRP) production car, the all electric i3. BMW’s goal is to get the expense of a carbon-fiber frame down to the level of aluminium by 2020. While only the passenger cabin of the i3 is made from carbon fiber with the drive train, battery and suspension attached to an aluminium chassis, it seems only a matter of time before 100% CF chassis like eVe become economically viable for mass produced road cars.

The next challenge for the Sunswift team is to make eVe the first road-legal solar-powered car in Australia. They expect it to meet Australian road registration requirements within as little as one year.

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A 'quick' test drive in a Tesla Model S P85+

Earlier this week EV News had the opportunity to test drive a Tesla Model S P85+ around the streets of Sydney. It was only a very brief experience compared to the week long test drives we've had with most other EVs, but it was long enough to confirm that Tesla Motors make electric vehicles that are in a league of their own.

The first thing you notice about the Model S is that it's a big car. All dimensions including wheelbase and track are larger than a full-size car like the Holden Commodore VF. The wheelbase seems governed by the size of the floor mounted flat-pack battery enclosure which makes up 700 kg of the vehicles 2,100 kg kerb weight. The upshot of this being the Model S has more interior storage space (1,796 L) than the Mitsubishi Outlander PHEV SUV we tested a few weeks ago.

For such a heavy car the weight wasn't noticeable while driving, although I am familiar with driving full sized cars and the test route didn't allow for any high speed loaded cornering. In acceleration the P85 Model S is stunning! Unlike all other EVs I've driven which have synchronous BLDC permanent magnet motors, the asynchronous AC induction motor in the Model S really gives a kick in the back off the line. So much so I'm thinking perhaps Elon Musk should consider issuing Tesla reps with neck braces for test drives.

The BMW i3 I drove in Munich earlier this year was, up until this week, the fastest EV I had driven. I noticed from a standing start, full off the line acceleration in the i3 didn't really come on strong until over approx 25 km/h, on it's way to 100 km/h in 7 seconds. With 310 kw and 600 Nm peak torque from zero RPM, the 3 phase AC induction motor launches the P85 Model S from a standing start to 100 km/h in just 4 seconds. That's faster than your average Porsche. As with all EVs, mid-speed acceleration was also impressive but with the Tesla, mind blowingly so!

One of the reasons I've been so keen to sample a Model S is because on paper it is the only EV that is broadly comparable to my current daily driver, which has 255 Kw / 475 Nm with a 1600 kg chassis. The 5.7 Lt 4 door sedan does 0-100 km/h in around 5 sec which is faster than both a standard Model S 85 (5.6s) and the 60 version (6.2s). I've clocked up over 300,000 km in this car so am very familiar with it's above-average acceleration, yet the Model S P85 absolutely kills it!

Ever since the Tesla test drive I've been trying to get my head around how the Model S P85's mid-speed acceleration could feel twice as fast as my ICE car. Multiplying the Tesla's 600 Nm peak torque by the 9.73:1 reduction gear ratio gives 5,898 Nm at the rear wheels. Divide that by the 2,100 kg kerb weight and the Model S has 2.8 Nm /kg. Running the same numbers for my Corvette engined family sedan gives 4,476 Nm (in first gear only). Divided by 1,600 kg kerb weigh surprisingly results in the same 2.8 Nm/kg figure.

So why does the P85 feel twice as fast at mid speed? The 3 phase AC, copper rotor, induction motor's torque curve gives a flat 600 Nm between 0 and 5,000 rpm. As with all EVs this broad torque curve allows the Tesla to have a single speed transmission. With the gear ratios commonly used in EVs they're effectively in the equivalent of first gear all the time. So while my ICE powered car has approx the same torque to weigh ratio in first gear, the V8 engine doesn't reach peak torque until 4,000 rpm (which accounts for the extra second 0-100) and rear wheel torque reduces with every up-shift of the gearbox until top gear where maximum torque is down to 'only' 1,000 Nm. By comparison, the Tesla has approx 6,000 Nm available on-demand from standstill up to 70 km/h. Over this speed electric motor torque starts to decrease but at 120 km/h the Model S P85 still has 3,405 Nm at the wheels.

The bottom line is, from a standing start the Tesla has full torque almost immediately (see dyno chart below) and at mid-speeds, due to the advantage of a permanent low gear ratio, the Tesla has up to 6x more peak torque available at the flick of the throttle pedal compared to my reasonably powerful internal combustion engine equipped car. There's no waiting for auto gearbox kick-down, it's just immediate torque at any speed. The results are... absolutely devastating acceleration from any speed and an almost permanent 'Tesla grin'.

When a start-up company like Tesla Motors can execute a new luxury car with such startling performance, 500 km range and running costs that are 1/10 th that of equivalent ICE cars, It's no surprise that Mercedes, Audi and BMW are already working on their own versions of the Model S. I don't think it's much of an exaggeration to say this car is revolutionary!

The Model S P85+ as driven was priced around $190k. A basic P85 option package with the full 310 kw / 600 Nm and 21" wheels is $130,600. Unfortunately luxury tax and other government charges add another $25k bringing the total cost to $155k in Australia.

(dyno torque curve from a Tesla Roadster - the Model S P85 has 2x more torque @ the wheels)

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Mitsubishi Outlander PHEV Plugin hybrid Test Drive [VIDEO]

Mitsubishi Australia were kind enough to loan EV News an Outlander PHEV for a week long test drive and we're not surprised it is already the best selling plug-in EV in Europe.

The Mitsubishi Outlander PHEV is the first 4x4 SUV to combine 'series' and 'parallel' hybrid systems. It has all the benefits of a plug-in electric car with a part-time duty cycle 87 kw 2.0 L 4 cylinder MIVEC (Mitsubishi Innovative Valve timing Electronic Control system) petrol engine that can run in either series hybrid mode, where it is used to top up the 12 kWh lithium ion battery mounted under the cabin, and/or can also runs in parallel mode to drive the front wheels.

The electric powertrain is based on 2x 60 kw / 166 Nm BLDC permanent magnet synchronous motors that run on up to 300 volts. It's a bit like having an iMiEV motor on each axle. Given the 1810 kg curb weight, EV mode acceleration is reasonable, but applying anything more than half throttle activates the ICE to assist. In this parallel mode the PHEV has a combined maximum output of 207 kw available for hard acceleration, which 'feels' like a V6.

Mitsubishi engineers have done an excellent job on NVH (noise, vibration and hashness) for the part-time duty cycle ICE (internal combustion engine) in the Outlander PHEV. Unlike the Holden Volt we drove last year where the ICE became fairly annoying after a few hours in the car, the ICE powertrain in the PHEV is so quiet that, without the assistance of the LCD 'energy use' dash display graphic, it's hard to tell whether the ICE is actually running or not!

The official ADR fuel economy rating for the PHEV is 1.9L/100km, with a maximum range of 824 kilometers from it's 45 liter fuel tank. I had originally planned to drive the PHEV to Melbourne (1,800 km round trip) to test highway range and the adaptive cruise control system (more on that later) but for business reasons the trip was postponed. Instead, during the 7 days I had the PHEV, I never needed to lift the fuel filler flap even once and returned the vehicle with more than 100 km range still indicated on the dash having covered 700 km of urban driving.

The vehicle was plugged in each night so we started each day with a full battery. The 12 kWh battery gives an EV mode range of approx 50 km. The PHEV provides a couple of options for managing your charge via two centre console mounted buttons. The 'CHRG' button allows the driver to manually turn on the ICE to charge the battery while the 'SAVE' button conserves battery charge and engages the ICE to drive the Outlander PHEV like a regular front wheel drive petrol vehicle. We were still experimenting with the save mode when we had to return the vehicle.

At highway speeds, aerodynamic load is at it's maximum and brake regeneration on expressways is minimal. Also, a electric cars battery contains a relatively small amount of energy (12 kWh) compared to a regular fuel tank (45 L x 9 kWh/L = 405 kWh). In an effort to make the most efficient use of the available stored electrical energy, we experimented with using 'Save' mode on any steady-state motorway with a posted speed limit of 100 km or more in an effort to save the battery for lower speed urban roads where brake regeneration can be maximised and losses such as aero resistance are minimal.

Unfortunately it wasn't a very scientific experiment so I can't provide any energy use figures. Even without using save mode at all the PHEV still achieves minimal fuel burn using it's own internal pre-programmed strategy of running the ICE in parallel mode at highway speeds so perhaps it would take longer than a 700 km test drive to get the most out of these manually operated features.

All Mitsubishi Outlander PHEV press cars are the top-of-the-range Aspire model which comes with a feature that seems perfectly suited to an electric powertrain, adaptive cruise control. As an EV powertrain can brake and accelerate with a single input from the throttle pedal, this allows seamless control of a vehicles variable speed relative to other traffic.

Adaptive Cruise Control was my favorite feature on the car and was turned on at every opportunity. In traffic it takes over everything but the steering. In built-up heavy traffic with speeds as low as 1 km/h the system will slow and accelerate in response to the traffic ahead without any driver input. In stop-start traffic the system can bring the vehicle to a complete stop, only signalling to the driver to push the brake pedal once the vehicle is stationary. The vehicle will not move away from a dead stop, but cruise can be resumed once over 10 km/h.

It was not uncommon to have the cruise control set to 80 km/h while only seeing 50 km/h on the speedo as the car responded to traffic. The driver can adjust the distance to the car ahead in three steps with a a steering wheel adjustable push-button. In addition this distance automatically adjusts according to speed, with the gap to the car ahead increasing at higher speeds.

The system also handles lane changing fairly well. When the driver changes lanes to go around a slower vehicle the system will respond to the clear lane ahead and accelerate to the set speed. The driver can also momentarily over-ride the system with throttle input to accelerate into a gap while lane changing and the cruise control will resume at the set speed once you lift off the throttle pedal.

One thing we were curious about was what the brake lights were doing in adaptive cruise mode. Apparently the low-speed auto brake system on the Ford Focus strobes the brake lights when active, but we were unable to confirm what was happening on the back of the PHEV in this mode?

As with most hybrids which mix regenerative and friction braking, the PHEV runs a brake-by-wire system with a servo operated hydraulic brake master cylinder. This enables the cruise control to apply friction brakes at very low speed to bring the vehicle to a complete stop. With Adaptive cruise control, driving in heavy urban traffic almost becomes relaxing! I honestly think the combination of regenerative braking and cruise control is the single best feature of the car and given the fact ABS and stability control are now mandatory on new cars, it seems only a matter of time before adaptive cruise control and autonomous braking also become mandatory features.

Speaking of stability control, the Outlander PHEV comes with Mitsubishi's Active Yaw Control (AYC) and Super All Wheel Drive Control (S-AWC). These systems were first developed for the rally homologation special Mitsubishi Lancer Evo. Given the SUV's high centre of gravity this is probably a very handy feature to have although there was no way I intended to push this vehicle to the limit to test it out. Perhaps the PHEV powertrain will soon be seen in something closer to the ground like the XR-PHEV EVO images recently released, then AYC and S-AWC could be actively engaged on winding country roads for purely entertainment value without the risk of tipping the vehicle over.

With a list price of $47,490 for the standard Outlander PHEV and $52,490 for the Aspire, it's little surprise the PHEV has shot to #1 plug-in on debut with 99% of all Outlanders sold being PHEV in several markets around the world.

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BMW i3 - is this the world's most desirable affordable electric car? [VIDEO]

During a recent visit to BWM world headquarters in Munich, EV News had the opportunity to test drive a BMW i3.

First impressions were all about the height of the seating position. This became more noticable in traffic where the i3 seemed taller than many SUV cross-overs. Unlike the battery in a Nissan Leaf where the cells are configured at various heights to allow space for footwells, the i3 battery is a uniform height and extends the full length of the cabin which results in a raised floor level.

Nissan Leaf battery

BMW i3 battery

However, whereas in a cross-over the seating & vehicle height would usually result in a high centre of gravity and poor handling, the combination of carbon fibre reinforced plastic (CFRP) cabin structure and below-floor mounted battery mass means the i3 doesn't suffer a huge amount of body roll. The limit of adhesion available from the bicycle like 155/70 R19 low rolling resistance tires might take more than a 1 hour test drive to fully exploit.

The i3 accelerates more like a sports car than a city car.

The extensive use of carbon fibre keeps the i3's curb weight down to 1,195 kg which is much lower then both the Nissan Leaf (1,500 kg) or the Chevy / Holden Volt (1,700 kg) we've test driven.

When combined with the i3's 125 kW BLDC electric motor, which is more powerful than either the Leaf (80 kW) or the Volt (110 kW), the result is a 0-100 km/h time of 7 seconds. Unlike a Tesla, the BMW i3 doesn't have an immediate kick off the line, but once above 25 km/h the EV torque really starts to come on strong. This may simply be the difference between the synchronous BLDC motor of the BMW versus the asynchrounous AC induction motors used by Tesla. AC induction motors are well known for enormous starting torque.

As with most EVs I've test driven the mid-speed acceleration is massively impressive. Gap shooting in heavy traffic takes on a whole new dimension and the i3 keeps pulling hard even when accelerating up to Autobahn speeds.

No EV test would be complete without mention of the regenerative brakes. Regen in the i3 is speed-sensitive, which means the car “coasts” with maximum efficiency at high speeds and generates a strong braking effect at low speeds. Regen braking is easily strong enough to bring the vehicle to a complete stop at regular traffic speeds below 80 km/h. Stop start driving in heavy traffic is a simple one pedal procedure, making the legacy friction brake system almost totally redundant in this vehicle.

In the video above Autocar's in-house retired racing driver Steve Sutcliffe, who seems to have a speak impediment once he says the word "gubbins', takes the BMW i3 for a thrash around their test track providing a good demonstration of the i3's cornering dynamics.

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On Holiday in Hawaii with the Nissan Leaf

During a recent holiday in Waikiki, a beach front neighbourhood of Honolulu in Hawaii, EV News took the opportunity to rent a Nissan Leaf for the day. Having scanned the available cars on the Enterprise Rent-A-Car web-site and noticing they had Nissan Leaf available and for approx the same price as others in the same bracket I couldn't resist test driving one.

We picked up our Silver 2013 Leaf with 544 miles on the odometer, fully charged and only a vague idea where we were going. Earlier in the week we'd hired a 3rd generation Toyota Prius to lap the Island of Oahu a couple of times. (I've driven a Holden Volt and a Mitsubishi iMiEV, but not a Prius so I had to tick that box)

Having just hopped out of a Prius the controls in the Leaf were immediately familiar. It wouldn't be a wild guess to say the mouse-shaped gear selector in both could be sourced from the same supplier. The start procedure in both is almost identical too, put the wireless key in the centre console, foot on the brake pedal, push button to start, select 'D' on the 'mouse', foot parking brake off, push the throttle and start moving forward - silently.

Aside from the steering wheel being on the wrong side of the car and having to drive down the wrong side of the road, (we're RHD here in Australia) we were still a bit navigationally challenged after only a few days in Hawaii. For a start, we hadn't been able to source an old fashioned paper road map of the place and being cheap skates (read: having a strong aversion to being ripped off) neither my better half nor myself had set-up International roaming on our iPhones so consequently they only worked when-ever WiFi was avaliable. Infrequent checking of Google maps required a quick visit to the nearest McDonalds to use their free WiFi.

Of course, the Leaf has GPS as standard built into the dash but a) you can't type in an address unless stationary (which frustrates the passenger no end) b) the address look-up isn't as good as Google and more often than not failed to return a result so it becomes a two device routine to actually find the route to any particular land mark.

I soon discovered range anxiety is real, at least within the first hour of driving an unfamiliar car. Like any typical Hawaiian day it was 30c so having driven out of the hire car lot and straight onto an expressway with the air conditioning on (i.e. maxium possible energy consumption)... the range indicator started to fall rapidly. Obviously if you owned a Leaf you would soon grow accustomed to it's range capabilities, but in unfamiliar terrain and in an unfamiliar electric vehicle, straight off the bat, it's all an unknown.

When we got the keys the range indicator said 84 miles (134 km). We hit a few outlet stores, hill climbed the 1,186 feet (361 meters) elevation to the Nu'uanu Pali Lookout, in the process depleting indicated range to less than 20 miles by the summit - which we regenerated back up to 37 miles (60 km) by the time we returned to our hotel by late afternoon.

Fortunately Hawaii has plenty of accessible public changing stations, which most of the time are very popular. (see above) Even though the parking itself isn't free, the charging is and as luck would have it, there was a charging station within 5 mins walk of our hotel. It was available when we arrived with our Leaf (although it had been ICE'd by a minivan – who promptly moved and starting asking questions about the Leaf) and after a quick 3 hours plugged in we set off for dinner with the dash showing 100 miles (160 km) of range.

When confined to level ground, city driving, as opposed to expressways and hill climbs, the Leaf consumes amazing little energy. What you use during heavy acceleration is mostly regenerated while pulling up at the next set of traffic lights. The leaf has the same blended brake set-up as the Prius and Volt so any use of the brake pedal kicks in more regeneration as opposed to dissipating energy through the friction brakes.

In fact, having driven 2 full laps of Ohau in a Prius, I now understand why Prius owners are often quoted as saying brake wear is minimal even after 200,000 km as like the Leaf and Volt, the Prius uses full regen braking most of the time. Incidentally, on a recent trip to Darwin to cover the World Solar Challenge it was interesting to note 80% of the taxis in Darwin are Prius – frugal on both fuel consumption and brakes - sounds like a perfect combination for a taxi.

From a drivers perspective, due to the “pedal feel simulator” in most hybrids and electrics, it's hard to tell the difference between regn and friction braking based on pedal feedback alone. The tell-tale is watching the dash displays ramp up to full any time the brake pedal is pressed while the vehicle is at speed.

For urban driving the Nissan Leaf is a great choice. It's surprisingly big for a 'small' car, costs virtually nothing to run, takes only a few hours to get back to fully charged on a 240v outlet and as we have seen with DC fast chargers it can easily cover 500 miles (800 km) in a day.

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