Published on July 11th, 2016 | by Paul Jennings and David Greenwood


Where does your car get its energy from?

The electric car is starting to make serious inroads into the mainstream market, but there’s still one major problem holding it back, and that is the battery systems. Up until now we’ve been used to driving vehicles powered by fossil fuels, storing over 45MJ of energy per kg in a tank costing a few hundred Euros to produce. For electric vehicles the storage is around 0.4MJ of electricity per kg. This means we need big, heavy (300-700kg) and expensive batteries if we’re going to come close to matching the range of the vehicles we’re used to.

So what needs to happen to address this, and be able to move forward with the production of electric vehicles which have a better range?

From a commercial viewpoint, batteries must get cheaper, lighter, having the ability to store more energy. From a consumer viewpoint, knowing that the car battery is going to last for the length of their journey and what to do when their batteries go wrong. There is also the economic and safety standpoint to consider.

Overall, affordability falls into both viewpoints. We need to research technologies to make future electric vehicles both capable and affordable to a larger market. Tesla has demonstrated that at the top end of the market, it is possible to deliver vehicles with excellent range – but with a price tag to match. Cars like the Nissan Leaf, BMW I3 and future Tesla Model 3 are lowering this barrier to entry, but are still at the high end of prices for vehicles in their category – even after government incentives.

One question is whether we need electric vehicles with an extended range – if charging is done conveniently overnight at home, with no need to visit a charging station then is a smaller range acceptable? We can liken this to the change in mobile phone batteries -when moving from GSM mobile phones with one-week battery life to smartphones which we mostly charge every night.

The average driving distance for a UK vehicle is about 25 miles a day, and 98% of journeys are less than 50 miles – so do we really need 200 mile range? Most large scale electric vehicle trials have shown that range is more of a perceived problem than a real one once the electric vehicle is capable of more than 60 or so miles real-world range. Once people get used to owning and running an electric vehicle, this is no longer reported as an issue. This is particularly the case where electric vehicles are used as second cars (typically urban run-abouts) or where manufacturers offer a mobility package alongside their electric vehicle sales whereby you can swap your electric hatchback for a Hybrid SUV for the few time a year you need to take the whole family a long distance on holiday.

Charging is an interesting issue too. The popular perception is that public infrastructure is holding up electric vehicle sales, but in practice, most electric vehicles are charged at home most of the time – as this is the most convenient for the user. Workplace charging is the next most frequently used, and provision for this is going at many companies and public facilities. The UK suffers from the lack of a joined up infrastructure, with many different charging operators – meaning that a nationwide traveller needs membership of a handful of schemes to access the network.

To extend the range of electric vehicles fast charging at strategic locations (such as motorway service stations) could have a significant impact, but it’s not easy to do. Different manufacturers have their own proprietary standards, meaning several types of fast charger are currently required. Whilst the number of electric vehicles on our roads are low, fast charging is great, but if you’re the second or third car arriving in a queue at a fast charger then you have a delay of well over an hour in your journey, more if the person charging has taken the opportunity to go for lunch.

When you fill a petrol car from a pump, you replenish the tank at a rate of energy flow of 30MJ/second. The best fast chargers manage 70kJ/second – 400 times slower. Fitting many fast charging stations to serve large numbers of vehicles isn’t trivial due to their very high power requirements – very quickly you get to the point of requiring expensive substations and high power grid connections to support this. In the longer term, this is what we’ll need, but it will require substantial investment.

Just like petrol, batteries contain a lot of energy, and if that energy is allowed to escape in an uncontrolled manner then it can cause an intense fire. This could potentially happen for instance if batteries are overcharged or punctured. Car manufacturers fit protective devices – both physical and electronic to make sure this doesn’t happen, but until we have fully autonomous driving, there is always the risk of a vehicle crash which may push these protection systems beyond their capability. By understanding how these failures occur, and designing battery cells and packs to avoid them, we can help take cost and weight out of the vehicle, and make the vehicle safer in extreme abuse conditions.

These are the big challenges faced by car manufacturers and ones that we are working to address. With support from the UK government, through OLEV, APC, Innovate UK, ERA and Catapult, we have a large number of projects underway, and we continue to invest in state-of-the-art facilities.  These projects and facilities aim to develop new knowledge, skills, technology and facilities to support UK industry seeking to use battery technologies in a wide variety of vehicle applications.

One of our projects for instance (Amplifii) is developing the next generation of traction batteries for electric and hybrid vehicles, along with a UK supply chain to deliver them. Through research into manufacturing technologies, it will combine the best human and automated assembly methods to manufacture battery packs and lay the foundations of a new UK automotive supply chain based around this technology.

We are also proud to be the electrical energy storage spoke for the Advanced Propulsion Centre, The UK Government’s support mechanism for taking automotive technologies from demonstration to manufacture. This puts us right at the heart of UK battery development. It’s an open facility, and partners are welcome to tap into our expertise. We’re already delighted to be collaborating with great universities like Imperial, Oxford and UCL in this area, and to be supporting new companies like Oxis and Faradion in developing their battery technologies.

A final thought to finish on – what do you do with the electric batteries when they come to the end of their useful lives? Repair them? Re-use them? Remanufacture them? Recycle them? It’s a hugely important topic given the amount and value of materials we’ll be using, but that’s for another blog!

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Professor Paul Jennings has been involved in research with the automotive industry for over 25 years, and now leads research and development on Intelligent Vehicles, Energy and Electrical Systems, and Experiential Engineering.

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