By ATN
Author: Mark Way, Chief Technical Officer, RML Group
Since first entering mass-market production, it can be argued that consumer demand has driven EV development almost as much as engineering innovation. The desire for longer ranges intends to overcome concerns over charging infrastructure, while a major focus on charging speeds tackles real-world practicality barriers.
Manufacturers can add larger capacity battery packs into their vehicles, extending their range by simply adding more cells, but this comes with a cost and weight penalty.
Significant advances in battery technology have resulted in higher capacity cells being developed and fitted in the same space envelope. As a result, long-range production EVs can now reach in excess of 400 miles on a single charge.
Despite progress, however, larger batteries require significantly longer charging times and are responsible for the greatest mass of any single component. Lighter cars are more efficient, but smaller batteries don’t offer the same range that drivers desire. It’s a fine point to balance, and one that can be greatly impacted by innovative developments.
New or existing technologies?
There are regular headlines talking about solid state batteries and other technologies, which use advanced materials to provide longer ranges and faster charging. While new battery technology developments will certainly come into play in the future, there remains plenty of potential to be unlocked in current batteries to improve both their efficiency and performance.
Batteries need to offer longer ranges, charge faster and continue to prove their safety, as well as use more sustainable materials and reduce weight. Despite dramatic improvements in the past decade, there is still a long way to go for EV batteries to win over some sceptics.
What’s more, economies of scale mean that the EV industry can rapidly evolve battery technology, but it must be feasible to produce at volume. Cost is also a prohibitor, with innovation hampered by the realities of affordability.
This is why using existing technologies in innovative ways is said to produce the greatest breakthroughs in the short-term, shifting the EV battery industry forward but at a realistic cost.
Effective cooling for better performance across the board
One of the key issues for battery management, regardless of whether it’s focused on efficiency, performance or charging, is temperature control. When in use, battery temperatures increase, reducing the efficiency and capability of the cells to perform as ideally required. This slows down charging rates, reduces energy output and reduces outright performance.
Most EV battery packs rely on air cooling to maintain temperature. For those who have driven an electric vehicle on the motorway for an hour or more, and then stopped to charge at a high power unit, they will be familiar with seeing a slower charging rate than the manufacturer quotes. It’s all down to a hot battery pack being unable to charge at high speed without overheating, so the management systems slow things down to keep the battery safe.
Some EVs have management systems that can pre-condition the pack to receive higher levels of charge ahead of stopping, and these are more effective at charging quickly on long trips. It is this active management that can dramatically improve charging performance.
The next stage of battery cooling
To further enhance battery management, companies such as RML Group have been developing immersed packs, using innovative fluids to draw heat away from the cells to keep the battery in optimum operating temperature.
These have initially been developed for use in a high-powered hybrid hypercar, with RML working alongside the manufacturer to produce a battery capable of being charged and discharged rapidly for optimum performance. The work is a continuation of developments RML Group carried out in motorsport, seeing the requirements of racing filter down into high performance road cars.
Using a dielectric coolant, battery packs can be cooled in a similar manner to traditional engine management systems, using a safe, non-flammable liquid with high thermal stability and poor electrical conduction characteristics. Pumped between the cells of a battery pack, it can take generated heat out of the module, cooling the unit and ensuring each cell is capable of operating to its maximum potential. The benefits of this see improved performance both in discharging and charging rates.
What immersive battery technology allows is a virtuous circle of development. Cooler battery cells can charge faster, reducing charging times, so a smaller battery pack is required to cover the same long distance, which reduces weight for a more efficient vehicle, and that then allows the battery’s energy to be used more efficiently.
Weight is the enemy of vehicle development, and for too long, electric vehicles have been overlooking this concept in the pursuit of longer driving ranges. Now, with the ability to extract greater performance, driving range and charging speeds from a pack, the trend for larger and heavier batteries can start to be slowed down and ideally reversed.
Smaller, immersed packs mean less weight, a greater amount of interior space and fewer materials used – all while still delivering the same long distance journey times on those occasions where a driver needs to recharge en route.
Although in the early stages of development, creating more efficient, faster charging and safer electric vehicles with smaller, immersion-cooled batteries is a crucial area for OEMs to focus on, without requiring the time-consuming and costly advances that researching an entirely new technology requires.
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