Recharge at Refuelling Speeds

| Transport

The Allotrope battery uses lithium-carbon technology

New Li-C battery technology offers fast recharging without loss of power density for use with short run urban delivery vehicles

Mahle Powertrain and Allotrope Energy have unveiled a new battery technology which offers ultra-fast recharging coupled with good power density. By combining the benefits of super capacitors and traditional lithium-ion batteries, the new lithium-carbon technology enables a full charge to be delivered in a similar time to refuelling an internal combustion-powered vehicle. In addition, Li-C cells are free from rare-earth metals, are fully recyclable, and are not susceptible to runaway events.

According to Mahle, range anxiety is often quoted as the main barrier to electric vehicle adoption, but if the battery could be recharged in the same time it takes to refuel a conventional IC engine vehicle, much of that worry goes away.

Dr Mike Bassett, Mahle Powertrain’s Head of Research believes that with the rise of the on-demand economy, there’s been a rapid increase in the use of petrol-powered mopeds for urban deliveries such as take-away meals, and this has contributed to air quality issues in cities.

“Decarbonising these deliveries has so far proved difficult without maintaining a stock of expensive interchangeable batteries or switching to a larger, heavier electric vehicle with increased energy consumption,” he says.

Small batteries with fast charge rate

However, in a collaborative project with Allotrope Energy, Mahle Powertrain has considered how an electric moped could be used as an urban delivery vehicle powered by an inexpensive small capacity lithium-carbon battery that could be recharged between stops in as little as 90 seconds.

Allotrope Energy’s lithium-carbon technology combines the benefits of super capacitors and traditional lithium-ion batteries to deliver a cell that can be recharged quickly and yet retains good energy density. The technology features a high-rate battery-type anode and a high-capacity electric double layer capacitor (EDLC)-style cathode, separated by an organic electrolyte.

The result is a battery cell with that suffers none of the thermal degradation effects experienced by traditional lithium-based batteries. Its stability, even at high temperatures, permits high current delivery and fast recharging, all without the need for complex external cooling or elaborate battery management systems.

Additionally, its capacitor-style cathode enables a lifetime of over 100,000 cycles, far greater than conventional batteries, while the elimination of rare-earth metals and the design’s complete recyclability make it better for the environment both during production and long after it.

Powering local deliveries

As part of the project, Mahle Powertrain investigated the scenario of a city-based e-moped fast-food delivery service with a 25 km target range. A 500 Wh conventional lithium-ion battery would require a recharge mid-shift that, even with a fast-charger, would take more than 30 minutes. In addition, regular fast charging reduces battery life to the point it would likely need replacement every year or two.

A lithium-carbon pack, however, could be recharged at 20 kW in just 90 seconds, meaning a full charge could be achieved in the time taken for the next delivery to be collected.

“With ultra-fast charging, the size of the battery can be optimised to suit the scenarios the vehicle will be used in, and that leads not only to weight savings but also cost reductions that further lower the barriers to decarbonisation,” Bassett pointed out.

The real challenge came in designing the electrical architecture capable of absorbing such high rates of charge so with no suitable charging systems on the market that can deliver these charge rates from a domestic supply, Mahle Powertrain created its own bespoke design.

The charging system uses its own built-in capacitor-based energy store to deliver ultra-fast charging up to 20 kW by augmenting the power from a typical 7 kW single phase connection, thereby reducing cost and complexity while eliminating the need for expensive power grid connection upgrades.

Case Study

At a seminar during the Cenex Low Carbon Vehicle trade show in September, Bassett put additional context around the need to move towards suitable electrification solutions for local delivery vehicles.

In a case study performed by the company, it found that fast food delivery scooters were predominantly used and were equipped with small engines with poor emissions and high noise levels. The vehicles regularly return to base and typically make 2-3 deliveries per hour over a 5 hour shift covering between 30 and 50km during that shift.

To demonstrate the concept, an eMoped donor vehicle was used and its batteries replaced with the Allotrope Energy battery. The vehicle is being used to prove charge time, range and life-cycle.

Fuel cell demonstrator vehicle

At the Cenex Low Carbon Vehicle show, Mahle Powertrain not only discussed the fast charging battery development with delegates but also showcased its latest activities in fuel cell technology.

Along with Bramble Energy, Mahle Powertrain has agreed to continue the collaboration to develop Bramble’s PCBFC hydrogen fuel cell technology with the phase 1 demonstrator vehicle being launched at Cenex. Bramble Energy’s innovative PCBFC technology significantly reduces the manufacturing cost of hydrogen fuel cell powertrains.

“Hydrogen fuel cells offer an alternative to the heavy batteries and long recharge times that other electric vehicle technologies suffer from, and that makes them particularly relevant to the commercial vehicle sector as it looks to meet net zero CO2 emissions targets,” said Bassett.

“Our work with Bramble Energy has demonstrated that their innovative PCBFC technology represents a cost-effective route to the adoption of fuel cell propulsion for commercial vehicles,” he continues.

Hydrogen fuel cells generate electricity using an electromechanical reaction rather than the combustion of a traditional engine. This not only eliminates harmful emissions but is silent in operation with no moving parts and produces only heat and water as by-products.

While conventional fuel cell stacks rely on stamped plates to hold the various layers, Bramble Energy’s approach uses PCB manufacturing technology, which can be produced cheaply, in virtually any shape using flexible production techniques.

Mahle Powertrain was chosen as the project’s integration partner due to its decade-long experience in powertrain technology integration and its expertise in EV control systems and thermal management.

The phase 1 results of the collaboration are based around a Renault Kangoo ZE delivery vehicle that sees a 5 kW Bramble Energy fuel cell integrated into the powertrain acting as a range extender. Future development will focus on creating a derivative with a higher power output and increased overall efficiency.

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