Battery-electric vehicles or BEV – albeit ones that are somewhat limited in scope, power and range – are nothing new in themselves. But the kinds of batteries required to move large, heavy vehicles like trucks and for long distances with heavy loads, or to power construction equipment in shaping buildings and infrastructure and moving vast amounts of material, are somewhat new. And what’s more, they’re constantly developing.
Let’s run through what makes them so special.
These are often simply referred to as batteries, but they are perhaps more accurately described as battery arrays or battery packs. They could also be called electric vehicle batteries or traction batteries. Each consists of hundreds or even thousands of lithium-ion cells linked together in modules and packs.
The battery packs need to be developed and produced in a way which is itself sustainable. They need to be cost-effective, efficient and useful: so that electrical transportation can remain within our customers’ price range and deliver worth over the lifecycle of their Volvo equipment. And they also need to be completely safe: one of the fundamental features of every product which bears the Volvo name.
So, the requirements are high. But the need for good battery-powered solutions is perhaps even higher. With this in mind, Volvo Group is dedicating a great deal of time and investment to the continued development of new battery technology – all for the sake of creating the most efficient and reliable batteries that we can.
The building blocks: lithium-ion cells
Lithium-ion cells are a common choice for vehicle battery packs. Lithium is what is referred to as the “energy carrier” in these batteries: the chemical that stores the energy in the battery. It’s particularly useful because it has a high energy-to-weight ratio. Given that the size of the complete battery array needed to power, for example, a heavy-duty truck is quite significant – and can lead to a lot of extra weight being added to the vehicle – this is an important factor. Battery packs can weigh around 500kg, and as many as six are placed on heavy-duty trucks. However, batteries are also developing fast, with the aim of increasing the capacity per kilo.
Lithium-ion cells also have a high power capability, both for charge and discharge. They can be optimized for energy storage, and for power output. When used in – for example – a truck, where they are used frequently and need to deliver a lot of power, these two factors need to be balanced out.
The lithium-ion cells are linked in parallel and then placed into strings, which in turn are used to create modules. Finally, around six of these modules become a standard battery pack. As many as 4500 cells can be used in a single battery pack, monitored and regulated by an on-board control system.
Each battery pack has an energy content of around 90kWh and so six in parallel, like you might find in a Volvo truck, has a total energy content of 540kWh.
The control systems – what do they do?
In order for the battery packs to be as productive, as safe and as long-lasting as possible, their usage needs to be optimized. As a result, there’s a control system inside every battery pack – making sure that the right conditions are maintained.
As anyone who’s had their mobile phone suddenly shut down on them in the winter can tell you, batteries are very sensitive to extremes of cold and heat. Cold temperatures increase the internal resistance of the batteries, reducing their efficiency. Too much heat, and the batteries will age quicker than we want them to. These control systems monitor temperatures, aiming to keep it within the 20-35°C “sweet spot” for optimum battery performance and lifespan.
The control systems also monitor power when charging and discharging, as well as the current state of charge – that is, how much energy is left in the batteries. In short, they optimize conditions to make the batteries perform as safely and effectively as possible.
In the future, they may also be given AI or machine learning capabilities to “learn” driving habits or equipment usage. They will then be able to adapt the battery pack’s performance according to things like route topology or charging routines.
What else needs to be done?
Battery-electric vehicles and equipment are one part of an overall solution. We at Volvo Group see them as one part of a three-part sustainable propulsion offering – alongside electricity-generating hydrogen fuel cells, which you can read more about here , and combustion engines that run on non-fossil fuels.
A battery’s capacity is also a factor that needs to be considered. Batteries have finite range and need to be charged. Given that many of our customers work internationally with transportation and logistics, there needs to be a widespread network of high-speed charging stations that are simple to access for everyone, across entire transportation routes.
Battery pack assembly in Ghent
