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SparkCharge 2 Tesla Model 1 by the water roadside

Extended range? May incur a charge

Image credit: SparkCharge

Standard EV charging stations are becoming a familiar sight. But do they represent the best charging technology for the future? Manufacturers are exploring different methods to minimise downtime when recharging electric vehicles.

Popularised by Apple in its smartphones, wireless induction charging, or Qi, charges a device using the energy from an electro­magnetic flux between two coils when they are aligned.

In Sweden, the town of Södertälje, south-west of Stockholm, uses hybrid buses in its public transport system. As part of the Wireless Bus Stop Charging research project, public transport operator Scania and the Royal Institute of Technology (KTH) conducted a trial where buses on the 755 service used wireless inductive charging along the 10km route. The charging boxes were installed on the buses and were lowered on the last stop of the route to access the wireless charger that was embedded in the road. Electricity passes across the air gap of around 100mm and the bus needs to be stationary for seven minutes to charge.

The nature of a hybrid bus means batteries also charge during braking and using the combustion engine. Wireless charging is silent and invisible and reduces the need for infrastructure such as overhead wires, although the trial buses still returned to the charging station to charge overnight. There may be temporary disruption to travellers as the road is dug up to place the wireless charger. According to Maria Xylia, a PhD research student at the Department of Energy Technology, KTH, planning and placement of inductive wireless charging around the route is needed, but if done successfully the energy consumption could be halved, using efficiently located charging stations.

Induction coils require some degree of alignment, and for charging vehicles that will be left in the same parking spot for several hours, researchers at Germany’s Fraunhofer Institute for Integrated Systems and Device Technology, IISB, have a new angle on inductive charging. They integrated coils into columns and vehicle number plates. Parking in front of the column reduces the gap and the size of the coil, from 800mm diameter used in floor-mounted systems to just 100mm diameter. The reduced size also saves cost. Coils are arranged to overlap in both the column and the number plate, so parking can be less than perfect as the current will flow regardless of the vehicle’s height and size.

Formula E Gen 3

The Formula E season may be stalled due to the Covid-19 pandemic, but the quest continues for EVs that change consumers’ perceptions, and tender application documents have been issued. For season nine, initially scheduled for 2022 but likely to be delayed, Gen3 Formula E cars will be required to have smaller, lighter batteries (180kg compared to Gen2’s 284kg). This will reduce the battery capacity by an estimated 51kWh, and as no battery swaps mid-race will be allowed, pit stops for fast charging may be introduced.

Races could include a single 30-second 60kW pit stop charge for each car, provided a cable and connector can be developed to transfer sufficient power in that time and which can handle the heat generated during the charge, which could be 450 or 600kW, and 80kW for a standard charge.

Qualcomm’s Halo static inductive charge technology is used for safety and medical vehicles around the Formula E circuits. In 2017, the company demonstrated its Halo Dynamic charging system, using the same hardware adapted to charge a moving car. Initially, the car charged at 10kW, but as power and speed increased, the vehicle received the same amount of energy in charging as it was expending on travelling at 100km/h. Two cars were driven along the same 150m stretch of road in Versailles, to show that multiple vehicles can be charged simultaneously.

Alejandro Agag, Formula E founder and CEO, observed at the time that a dynamic charging lane raises the possibility of a 24-hour race without stops.

Peer-to-peer charging

When a vehicle’s battery is low, another vehicle could, metaphorically, extend a helping hand. This is the idea behind Peer-to-Peer Car Charging (P2C2) proposed by a team at the Department of Electrical and Computer Engineering at the University of Florida.

The system is based on the same principle as aeroplanes refuelling mid-air and could apply to autonomous fleet vehicles. A cloud-based central control system would connect paired vehicles. Once aligned, a telescopic arm, with a charging port, could extend from the donor to the receiving vehicle for a mechanical connection. A model simulation using robo-taxis showed that vehicles saved time by stopping 65 per cent less and that the battery capacity was reduced by around 25 per cent.

Portable power

All of the above are based on the EV arriving at a charging point. A start-up, SparkCharge, brings the charge to the EV. It has developed portable, fast-charge, modular units that can be accessed via a phone app, a smart speaker, or via roadside assistance companies.

Pilot programmes in San Francisco and Los Angeles began in May this year, using a 17.5kW charger. The two-part system consists of a battery module with cylindrical lithium-ion cells which is connected to a charger, capable of up to 40A continuous output and 500V maximum for a mile-per-minute charge. Battery modules can be stacked to increase the storage capacity.

Initially, the system is offered in the quick-charging CHAdeMO protocol, up to 62.5kW by 500V, 125A DC charge. This is up to 14 times faster than Level 1 charging (using the EV’s cable plugged into a 120V outlet) and up to six times faster than Level 2 charging at 240V with a dedicated cable.

 

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