Wassaf Akhtar Mohammed | 30/08/2021
This article focuses on best practises on how the eVTOL (electric vertical take off and landing aircraft) companies can leverage the capabilities of current battery swapping technology on certain mission like Ambulance services and the optimal pros and obvious cons that come out of it. Are the batteries there yet to drive this revolution?
Battery Swapping is a process in which a drained battery is exchanged for a fully charged battery at a Battery Swapping Station or BSS. Analysis done for an eVTOL air ambulance mission revealed that the total battery density requirements are significantly high during hovering mode and lesser in cruise mode. At an average battery charge maximum power setting of 125 kW, we found that eVTOL’s preparation time (an undesirable feat in such missions) was significantly higher due to high battery charging times. Given high re-charging times, in this scenario, air ambulances relied on swapping batteries when eVTOL returned to the base after each mission to reduce the total call time. Battery swapping was assumed to take around 5 minutes rather than getting the current battery recharged which would take around 25 mins even while using todays high performance Tesla charger.
Advantages of battery swapping
· Swapping only takes a few minutes which is faster as compared to conventional fast and slow charging for a fully charged UAM vehicle.
· Charging at high ambient temperatures can lead to degradation of the battery after some time. Whereas swapped batteries can be charged in a controlled environment via slow charging to prolong battery life.
· Empty batteries that are swapped out can be charged when electricity is cheap or demand is low.
· Unlike with battery charging stations, ‘the physical footprint of battery swapping is materially less since it’s more or less just a series of small storage compartments for batteries.
· eVTOL batteries can lose range over the years. But with a swap system, battery life can be prolonged.
· Organised swapping operations allow for systematic disposal and recycling of used batteries.
Cons of battery swapping
· Infrastructure -High installation cost of the battery swap station. The infrastructure required for the battery packs is immense and much more complex and expensive than charging.
· Compatibility-For a technology to succeed and become a dominant trend, one feature is absolutely essential: Cross Platform / Brand Compatibility. For battery swapping to ever have a chance at becoming a mainstream technology, interchangeable battery packs that are similar for various manufacturers must be found. Manufacturers would all design their UAM vehicles based on proprietary designs. Using all a standard format battery pack would limit the manufacturer’s flexibility and innovation. Also, there are several battery cell manufacturers and each manufacturer would side with a single supplier for his cells.
· Battery pack design-One of the first issues that battery swapping technology faces is battery design. In battery swapping, the batteries must be easily accessible and located in a single pack.
· Demand and supply of Batteries at charging stations-As demand for batteries and battery swapping centers increases there are chances of cost overruns due to transportation of batteries from one center to another. Since batteries are heavy, there will be additional cost involved in transportation.
Cost of battery today per kWH -According to Bloomberg NEF which has been tracking battery costs, currently it is at averagely 100$ per kWH
At an average cost per kWH of 100$, we envision as we begin manufacturing the batteries in bulk, in economies of scale, the price will significantly drop down to 40$ by 2030 which in turn drives the operating cost of the eVTOLs throughout its lifecycle. With this conclusion, can we rely only on battery swapping technology and not any other alternates? How about Hydrogen? which brings my next blog to give an insight into “Why hydrogen is the best solution for eVTOLs?).