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Electric Vehicles Set to Reap Dividend

The second season of the all-electric racer championship opens the door for teams to develop their own drivetrains, boosting road-going technology.

By Steven Keeping

When Mouser-backed driver Nelson Piquet Jr. captured the first-ever FIA Formula E championship in June, 2015, the competition waved goodbye to the identical-car format and looked forward to a second season where drivetrain development was opened up.

Formula E is an official Fédération Internationale de l’Automobile (FIA) single-seater championship. Season two commenced in China in October and will continue through to June 2016. The championship will compete in the heart of ten of the world’s leading cities.

Piquet Jr.’s China Racing team’s success was backed by Mouser Electronics, and along with partners Molex and Vishay Intertechnology sponsored the Spark- SRT_01E EV, which was capable of 0-to-100 km/h (0-to-62 mph) in three seconds and a top of 245 km/h (150 mph). But it’s testament to Piquet Jr.’s driving talents that he won the inaugural championship in exactly the same vehicle as his fellow competitors.

According to the the CEO of Formula E Holdings, , Formula E is a test bed for electric vehicle (EV) technologies such as batteries, motors, transmissions and charging. On the launch of Formula E, Agag promised that after season one the teams would be able to independently develop the car. True to Agag’s word, season two has seen the teams come up with their own drivetrain solutions.

For Formula E’s second season, Mouser Electronics, this time with partners Molex and Panasonic, is sponsoring Jay Penske’s team with drivers Loic Duval, winner of the Le Mans 24-hour endurance race in 2013, and European Formula Master Champion Jerome D'Ambrosio.

Figure 1: Loic Duval is one of the drivers for Mouser-sponsored Dragon Racing in season two of Formula E. (Source: Dragon Racing)

Slow to Catch On There is little doubt that the EV––a car driven by one or more electric motors powered by batteries recharged from an external electricity supply––is here to stay.

Models such as the BWM i3 (featuring a 125 kW (168 bhp) electric motor, 22 kWh Li-ion battery, 130 km (81 mile) range, 0-to-100 km/h (0-to-62 mph) in 8 seconds, 150 km/h (93 mph) top speed), Chevrolet Spark EV (97 kW (130 bhp) electric motor, 21.3 kWh Li-ion battery, 132 km (82 mile) range) and the sporty Tesla Model S (310 kW (416 bhp) electric motor, 85 kWh Li-ion battery, 425 km (265 mile) range, 0-to-100 km/h (0-to-62 mph) in 4.2 seconds, 210 km/h (130 mph) top speed) vie consumers’ attention.

EVs provide instant throttle response, delivering smooth power all the way up to top speed. Recharging takes place overnight, eliminating trips to gas stations. Moreover, the simplicity and energy efficiency of an electric motor is 75 to 80 percent compared to a gas engine at 25 to 30 per cent, making EVs less expensive than conventional vehicles to run and maintain. Lastly, EV are clean, producing no tailpipe emissions.

Despite the advantages, EV uptake is a lot slower than car makers would prefer. Many consumers are put off by EVs’ drawbacks. Chief among these is range, and “range anxiety” is near the top of the list of reasons why consumers don’t buy EVs.

The second key objection is price; EVs are expensive. The current crop of EVs is mostly priced between $30,000 and $40,000, considerably more expensive than comparable midsized conventional vehicles such as the under $20,000 Honda Fit and Ford Focus.

Finally, EVs can take a long time to recharge compared to pulling in to a fuel station and pumping a tank of gas. According to America, for example, a full charge for the Leaf, the world’s most popular EV at over 200,000 units shipped, takes around eight hours from a standard household 220 or 240 V outlet.

Figure 2: The Nissan Leaf is the world’s most popular EV. It costs around $35,000, with range of 135 km (84 miles) from its 24 kWh power pack and takes eight hours to fully charge. (Source: Nissan America.)

Faced with these challenges, how will Formula E’s second season help it deliver on its promise to improve road-going EVs - and thereby attract more buyers?

Boosting Energy Density Key to EV technology’s development is the freedom Formula E teams now have to work on the drivetrain (“Everything behind the battery” according to ABT team Formula E driver ) - arguably the area where trickle-down developments are most beneficial to EVs.

Figure 3: A Formula E racing car’s drivetrain. ((At top of picture) Battery pack with battery management and inverter on top, (midsection) electric motor/generator and (at bottom) gearbox driving rear wheels.) (Source: Formula E).

The chassis, designed and manufactured by Italian company , and strong enough to be fully compliant with the 2015 FIA crash tests, is unchanged from last season.

While the battery pack remains identical between teams, manufacturer Williams Advanced Engineering has made some improvements. The battery weight and capacity are still limited to 200 kg (440.9 lb) and 28 kW/h and maximum power is 200kW for qualifying, but power has been increased to about 170 kW (from 150 kW) for the race. Under typical race conditions, the battery lasts 25 to 30 minutes. (Two cars are used to complete a 50 to 55-minute race as swapping out a battery pack is impractical.)

Williams now has a full season of data from ten teams over ten different tracks in order to refine the battery pack’s management software. This allows for more efficient use of the power, for example, helping the driver to accelerate harder out of the turns, while ensuring the car still has the battery capacity to complete at least half the race. The software has a significant impact on a ’s performance because power delivery (and battery regeneration) is determined by a “shaping map”, or lookup table, in the management unit’s memory. When the driver presses the throttle, a look-up table in the engine control memory uses its position to determine how much torque needs to be delivered to the motor. The shaping maps are different for each circuit.

Figure 4: The Williams Advanced Engineering battery pack for 2016 offers more race power and improved management. (Source: Formula E)

Battery development spin-offs from Formula E are one area that would be a major boon to road- going EVs. Panasonic is a leader in battery technology and has years of research in extending the life of EV batteries. While energy density developments in the second season of Formula E are limited, from season three, teams will be able to develop their own power packs (although still restricted to the 200 kg weight limit) with a view to doubling the energy density and running a single car for the entire race by season five. Such technology would banish range anxiety if applied to road-going EVs.

The DC power from the Li-ion battery pack is converted to AC to drive the Formula E car’s electric motor(s) by an inverter. Information about the teams’ inverter technology is limited, but it’s a fair bet that all use a highly-efficient (95 percent plus) DC-to-AC unit coupled to a Variable Frequency Controller (VFC) powering a three-phase synchronous induction motor. The VFC is the most efficient control system for regulating the speed of an electric motor under the varying loads experienced by EVs. Essentially, the motor rotates at the same frequency as the controller, so increasing the frequency accelerates the car. Formula E motors can rotate at up to 20,000 rpm.

AC synchronous motors do away with the (brushed) mechanical commutator employed in traditional electric motors, replacing it with an electronic device that improves reliability and durability. Another advantage of this type of motor is that it can be made smaller and lighter than a brush type with the same power output.

In the first season teams used a “motor-generator unit” (MGU) from McLaren Electronics Systems. The MGU has the highest power-to-weight ratio (7.7 kW/kg; 4.7 bhp/lb.) of any electric motor in the world, delivering up to 200 kW (270 bhp) from a unit weighing just 26 kg (57.3 lb.). In comparison, a 2015 Formula 1 engine has a power-to-weight ratio of around 3.85 kW/kg; 2.34 bhp/lb.).

Things are bound to improve further for the second season as teams are now allowed to design or source their own motors. Mouser-sponsored Dragon racing, for example, has elected to equip its car with a power unit from French EV maker . Other teams are choosing to go with two motors while still others are choosing to stick with the proven McClaren unit.

Last year, all the Formula E teams used a paddle-shift, five-speed sequential gearbox from maker . This year the nine teams have come up with eight different transmission solutions. Some teams are using four gears, others three and some just one. Some have even stuck with the same technology as last year reasoning that its proven technology with high reliability.

Electric motors produce high torque from almost zero revs and the torque curve is virtually flat - so a single gear to drive the vehicle from a standstill to top speed is a viable option. Another advantage of eliminating or limiting gear changes is that each shift takes time - admittedly only fractions of a second, but still enough to win or lose races. Shifting gears also interrupts battery regeneration through energy harvesting.

So why bother with any gears at all? In a word, efficiency. While the electric motor power curve is wide and torque curve flat, the efficiency curve is anything but. Using gears allows the motor to operate in the most efficient range for a given speed enabling the car to either move faster for a given power output from the battery, or, alternatively, increase the range for a given speed. The evolution of Formula E will soon sort out the best compromise between speed and efficiency.

Shared Anatomy The advances resulting from Formula 1 took years to feed down into the cars we use every day because the engineering of the racers was radically different. Formula E will produce quicker dividends because, under the skin, the anatomy of the single-seaters and road-going EVs is similar. Generally, both use Li-ion battery packs in the 20-to-30 kW range, DC power is converted to AC via inverters and VFCs, and brushless AC motors use the energy to drive the wheels via a single or a few gears.

In addition to encouraging higher energy density, Formula E also promises to address the time it takes to recharge EV batteries. Li-ion technology features a long trickle-charge ‘tail’ to its charging profile, but it’s possible to rapidly charge the cells to around 80 per cent capacity in about 25 per cent of the time it takes to fully charge. New 50 W wireless charging systems could allow mid-race “refueling” to replace the current Formula E car changes. Such rapid wireless charging technology would also provide an excellent solution for EV drivers short on time; by parking in suitably- equipped spaces the car could receive perhaps a 50 per cent charge in the time it takes to grab a coffee - without even having to fuss over a connector.

The major automotive makers that take part in Formula E are keen to rapidly push such developments into their commercial EVs in order to stimulate the market. (And others, such as Nissan and BMW, are rumored to want to get in on the action by entering teams next year.) Greater range and better performance are likely to convince consumers to switch to greener motoring. And the more car buyers switch to EVs the cheaper they’ll become. In a world fighting to cut carbon emissions, the spin-off technology that results in better road-going EVs could prove to be Formula E’s greatest dividend.