Is battery swapping the solution for the EV charging problem?

20-04-2022 |   |  By Robin Mitchell

While EV technologies continue to improve, the lack of charging ports and the high cost of EVs continues to make their adoption difficult. Why are charging ports problematic, how would a battery-swapping scheme work, and is it a practical solution?

Why are charging ports for EVs problematic?

Despite what many may think, Electric Vehicles (EVs) have been around longer than the internal combustion engine meaning that the first cars were in fact electric. However, such vehicles were extremely rare (if not prototypes), and the high energy density of liquid fuels made their use far more practical. Thus, it has only been the past two decades that battery technologies have improved enough to make electric vehicles practical.

But even with the many advances in battery technologies, they still suffer from some major issues that see their adoption significantly slowed. One of these is their low weight to energy ratio meaning that batteries are extremely heavy compared to gasoline. Simply put, this ratio prevents heavy goods vehicles from ever being entirely electric as the need for a long-range requires a large battery. This large battery reduces the amount of weight that the truck can pull, which reduces the profitability of transport.

Another major challenge faced with EVs is their long charging times. While great strides have been made in charging technologies for EVs, getting any decent range can still require half an hour for the average EV or around 15 minutes for higher-end vehicles. Even then, this is far too long for use in petrol stations where cars can typically be filled up and paid in under a minute; imagine the chaos of trying to charge just 10 cars with only four charging points available.

To add to the list of chargers' problems, their availability is somewhat sparse. This is particularly a concern for those who live in residential areas relying on on-street parking as charge points on streets are extremely rare. Thus, electric vehicles are generally only available to those who travel to work with an electric charge point at their place of work or in their private driveway.

How would a battery-swapping scheme work?

Batteries in EVs are extremely expensive, and their slow time to charge makes them impractical for use in petrol stations. However, one possible solution could alleviate this issue: battery swapping.

The battery of an EV would be an easily interchangeable part that is disconnected and replaced with a fully charged unit at a petrol station. The battery itself is not owned by the user, but instead, the charge stored on that battery is used. The old battery is charged at the petrol station (along with others), and when these are fully charged, they are given to new vehicles coming in needing a topped-up battery.

If a modular battery could be designed, it would allow for battery changes to happen in seconds, allowing EVs to use petrol stations similarly to fossil fuel-driven vehicles. The use of swappable batteries would also remove the need for vehicle owners to install charge points at their homes while also removing the need for charge points in car parks and streets.

Furthermore, battery swapping may allow car manufacturers to significantly reduce the cost of EVs by removing ownership of the battery from customers. Instead, using a standard open design for batteries (such as AA, AAA, and PP3 9V) could allow any manufacturer to create a battery that is then paid for every time it is recharged. The use of a serial number would ensure that the correct manufacturer receives the payment, which can help manage the eventual recycling of the device.

Is a battery-swapping scheme practical?

The idea of battery-swapping in EVs is not new, and some believe it is a good solution to the EV problem. However, it doesn’t take much examination to realise the many potential problems it faces on both technical and economical fronts.

From a technical standpoint, cars are generally designed in a way that makes their internals highly inaccessible. Creating a back port that opens up to expose the battery for removal would require a car designed fundamentally differently. The weight of batteries (around half a ton) means that swapping a battery could only be done practically with a robotic system. Such a robotic system would need to be accurate and precise, and trying to do this at speed with drivers coming in and out would amplify the challenges involved.

From an economic standpoint, petrol stations would need to stock more batteries than cars being serviced as the time for batteries to charge remains fixed. Essentially, to get electric vehicles in and out in a reasonable amount of time requires batteries that are already charged, and assuming a petrol station can service one EV every two minutes, that requires a total of 7 batteries on continual charge (assuming a 15-minute charging time with a 2-minute swapping time). Considering that batteries are a major cost component for EVs, this would be an expensive setup.

The infrastructure needed to automatically change batteries would also be expensive regarding R&D and implementation. The complexity of such a system would also make autochangers expensive to maintain and replace.

It should be noted that battery swapping schemes are being used by one company in China called NIO which has claimed to have performed over 500,000 swaps by 2020. But these swaps are only on NIO-made vehicles using batteries that they have developed themselves. Another company called Better Place, raised $800mn in funding to produce a battery swapping technology, but this project eventually went bankrupt after failing to execute its plans.

Overall, the idea of a battery swapping scheme may work well if the batteries themselves are extremely small providing a hundred miles at the most. But for a system where cars expect to get more than 200 miles, the practicalities of such a system quickly diminish.


By Robin Mitchell

Robin Mitchell is an electronic engineer who has been involved in electronics since the age of 13. After completing a BEng at the University of Warwick, Robin moved into the field of online content creation developing articles, news pieces, and projects aimed at professionals and makers alike. Currently, Robin runs a small electronics business, MitchElectronics, which produces educational kits and resources.

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