EVA. Click to enlarge.

EVA is propelled by a 60 kW, 223 N·m (164 lb-ft) motor; top speed is 111 km/h (69 mpg), and acceleration from 0 to 100 km/h takes 10 seconds. Power is supplied by a 50 kWh battery pack, comprising 216 63 Ah lithium polymer cells.

EVA’s monocoque structure is made entirely of carbon fibre reinforced polymer (CFRP) and is one of the largest that has been made of this material. This translates to a lightweight body (150 kg less than steel) without compromising on torsional stiffness and strength

A key highlight is the car’s super-fast charging system, facilitated by twin charge ports. EVA is designed to be recharged in just 15 minutes to cover a realistic range of 200 km (124 miles) based on Singapore driving patterns. Under US FTP 72 standards, a single charge could propel EVA for 330 km (205 miles), according to the TUM CREATE team.

The challenges surrounding fast charging include the high electric currents needed and the heat that is consequently generated in the battery pack during the recharging process. TUM CREATE engineers designed an innovative concept for more effective thermal management of the battery cells that targets to extend the pack’s lifespan.

At the EVS 27 conference in Barcelona, engineers from TUM CREATE presented a paper on the accelerated ageing tests they performed on the large format lithium-ion cells for EVA.

The cycling involving fast charging at 3C was aimed to charge the battery pack of an EV in 20 min. In a real application, repeated fast charging could be needed and sufficient cooling is required to keep the battery pack temperature from exceeding 28 °C. When the battery ages due to capacity fade and power fade, the average temperature of the battery pack increases, therefore more cooling power is required to keep it from exceeding the target temperature.

—Arunachala et al.

TUM CREATE’s researchers have also developed an individualized, overhead air-conditioning system with which they target to reduce the cabin cooling power. Ergonomics studies have shown that localized cooling has a direct impact on the overall thermal comfort. The overhead outlets and the seat ventilation target these areas to create better thermal comfort without the need to cool down the whole cabin. Unoccupied zones can also be switched off to further reduce energy consumption. This system also reduces the exposure of air-borne particles or germs from being blown from one seat to another zone in the vehicle.

Besides the cabin cooling system, EVA’s innovative seats provide a maximum comfort for both the driver and passengers driving in humid tropical climate. The ergonomically designed seats are equipped with a purpose-built system where suction draws away moisture and heat from the surfaces of the seat. In addition, the front passenger seat folds forward to reveal an integrated child seat for children aged 9 months to 3 years old, which fills the void in the area of safety for young taxi passengers.

The climate controls, in-car entertainment, booking and digital payment systems are also linked via the infotainment system that allows passengers to control air-conditioning and audio settings wirelessly from their personal mobile devices. Similarly, the central control panel and driver’s instrument cluster are also connected seamlessly to the on-board systems, and are able to provide driving statistics and power-saving tips to the driver.

Transportation companies around the world typically re-purpose passenger cars as taxis. However, the challenge of current electric vehicles is the extremely limited range and long recharge times (up to 8 hours), making them impractical as taxis. TUM CREATE aims to address these issues, as well as the unique challenges posed by the heat and humidity in tropical megacities, through its research and development. Unlike temperate climates, passenger cooling and battery pack heat management are issues specific to tropical and equatorial regions.

As a form of public transportation, introducing e-taxis into the local taxi fleets has a high leveraging effect to decrease carbon emissions.

While taxis account for less than 3% of the vehicle population in Singapore, they contribute to 15% of the total distance travelled. The average two-shift taxi covers over 500 km [310 miles] a day.

—Principal Investigator Dr. Daniel Gleyzes

Resources

• Raghavendra Arunachala, Kamyar Makinejad, Satyajit Athlekar, Andreas Jossen, Jürgen Garche (2013) “Cycle Life Characterisation of Large Format Lithium-ion Cells” (EVS27-4750252)