The Automated Charging Decision Tree
Wireless power. Robotic charging. Battery swapping. These technologies have sizzled, faded, and risen again like a phoenix throughout the years, from Better Place and Tesla’s swap stations in 2013 to Tesla’s “robot snake” charger in 2015 to Volkswagen’s cute garage robot in 2019. Yet aside from China, which has backed a national standard for battery swap stations, manual DC fast charging (DCFC) and Level 2 (L2) charging remains the dominant priority for most countries.
Interest in automated charging has recently revived because of two trends: the early commercialization of autonomous vehicles and the electrification of fleets. So it seems worthwhile to revisit the conversation — when does automated charging make sense, and what should potential adopters consider before committing millions of dollars?
The strategic vision
As any lean startup acolyte will preach, we should start with the use case rather than try to fit a predefined solution to a problem. On a strategic level, there are at least three things to consider.
First is the type of fleet and resulting usage pattern, because this will dictate when you want to charge and how fast that charging needs to be. Private consumer vehicles will likely have long dwell times at their workplace or home, but behavior can be quite stochastic so you can’t rigidly schedule around it. If a consumer doesn’t have access to workplace or residential L2 charging, they’ll have to rely on public DCFCs.
On the other hand, most fleets have consistent schedules. Some, such as garbage and last-mile delivery trucks, regularly dwell overnight at depots, which means there is plenty of time to charge at a relatively low speed. Others, such as slip-seated trucking, operate close to 24/7 and therefore have less time to charge at a base; they will need a way to quickly replenish along their routes. A third type of fleet is decentralized (think rideshare drivers) and will act somewhere between consumers and commercial fleets.
Second is planning whether your charging facilities will be internal or shared. Internal sites are more amenable to using bespoke charging equipment to optimize your operations, but require far more in-house expertise and CapEx. Sharing sites with other fleets can greatly improve the utilization of equipment and enable you to amortize upfront costs or leverage third parties, but limits your depot design to the lowest common denominator. For example, if you want to use wireless charging, there will be far fewer partners who can also charge wirelessly.
Third, you should evaluate how much site coverage you need and the impact on deadhead miles. If returning to centralized depots does not incur much cost, it may be economical to build a few large, internal sites. On the other hand, if returning to distant depots means missing out on potential revenue generation, you’ll probably want to charge as close to your customers as possible. This means you’ll either need to build out many smaller charging facilities and incur higher overhead costs, or leverage existing sites where relying on partners makes automated charging technologies less appealing.
Generally speaking, wireless charging is more readily available for lower-power L2 charging, because the coils for transferring energy can be smaller and more easily integrated into vehicles. Robotic charging makes more sense with DCFCs with high throughput, because you can amortize the CapEx across more charging sessions. Battery swapping is useful if you need a full charge in less than 20 minutes, which is likelier for fleets that have to operate near 24/7. Both wireless and robotic charging make more sense at internal facilities (think warehouses and logistic yards), but new approaches to battery swapping mean they can be relatively distributed. Of course, there are exceptions to this simplified approach, and the technologies continue to evolve.
However, once we go deeper we open multiple cans of worms. Seemingly small tactical needs can make or break the case for automated charging.
The first major consideration is vehicle integration. Wireless charging will require building a receiver pad into every vehicle. This adds weight and cost, and takes up space that could otherwise go to the battery pack, reducing energy density.
Battery swapping will also require designing a compatible battery pack. The extra packaging and connectors will likewise add weight and cost, and consume space that again reduces energy density. Swapping may also reduce reliability by increasing mating cycles and introducing new problems that traditional charging doesn’t encounter, such as dirt and water ingress. The most difficult challenge, however, is a business problem. Unless every automaker creates their own siloed battery swapping system, they’ll need to share proprietary technical details with battery swap providers (e.g. cooling systems, battery specs). This may be one reason why Better Place never got more than Renault’s 80-mile range Fluence integrated with their system. As Lawrence Ulrich writes,
The design of each automaker’s batteries is deeply entwined with unique vehicle architectures. Imagine Elon Musk, and the automotive giants racing to catch up with him, calling a competitive truce, and working hand-in-hand to standardize every battery, brand and model. Any automaker…would be cutting their own throat, and handing potential competitors the knife.
A second consideration is depot design. Does it look like a parking lot or a truck stop with lanes? Charging lanes generally lend themselves to high-throughput operations; a line of vehicles simplifies installation of robotic equipment that you could place on a rail to service multiple chargers. (Of course, you need to make sure your vehicles’ charge ports are all facing the robot!) Will you have closely-packed vehicles or do you want drive aisles and additional space? Closely packed lots may benefit from wireless charging ground pads, since you don’t need to allocate space for boxy charging cabinets.
Third, how automated are the rest of your fleet operations? If we assume that more and more vehicles will have automated systems — not necessarily full self-driving but at least a self-park feature — then it’ll be far easier to navigate vehicles accurately and precisely for wireless and robotic charging and battery swapping. There might even be potential to reduce the cost of robotic charging by placing the “robotics” on the vehicle side — the charger itself could be a simple plug that the vehicle navigates into!
A fourth consideration is labor availability and cost. If staff are already present at a charging facility, potential labor savings from automating charging is relatively low and may not compensate for higher upfront costs. This is even more true when considering that robots and battery swap stations have moving parts that are more likely to break down.
Finally, what edge cases might the operating environment throw in the way of charging? Some Tesla Superchargers connectors have experienced ice buildup that prevents users from fully plugging in. Wireless charging is less likely to have issues with this, although they often have safety features that prevent charging if a metallic object is in the way (some metals can heat up similar to cooking on an induction stovetop). Pick your poison.
Putting it together
What does this mean for each of our automated charging options? Wireless charging claims to be more convenient for consumers since they don’t need to plug in to charge. However, this simple act may not be as bothersome as it’s made out to be for a private EV owner. Wireless charging does enable fleets to reduce labor costs, but if you’re in a centralized depot with existing staff, any additional labor cost may be minimal. On the other hand, it can eliminate the need for staffing at smaller distributed charging locations. For some applications, wireless charging will enable smaller batteries (or longer range and uptime) by having vehicles “power snack” throughout the day during short pit stops like bus stops and taxi queues.
Robotic charging proponents also claim labor savings, but as with wireless charging, potential adopters should run their own calculations at centralized depots. It’s unlikely companies will put expensive robots in more distributed (and potentially public) charging sites with less control over public interactions. The benefits of robotic charging are really in places you don’t want to staff, but which are internally controlled, such as certain areas of ports and warehouses. For these locations, robots could better handle bulky charge cables required by higher-power charging of heavy-duty vehicles, or obviate the protections typically required of equipment operated by humans. Autonomous vehicles might simplify the controls required on the charging station side by performing the positioning themselves. Of course, there are many types of robots. The VW robot seems useful since it eliminates the need to install fixed equipment — and rather than requiring consumers to search for charging in a garage, the charger comes to you.
Finally, battery swapping. The main benefit here is that consumers or fleets don’t need to wait for charging, which even at today’s fastest chargers takes over 30 minutes. It appears unlikely that consumers will change their habits and embrace swapping such an important piece of their vehicle (although NIO seems to be changing this in China). The key opportunity appears to be fleets, where the negative impact on energy density may be offset by higher uptime through swapping. In addition, a major barrier to fleet adoption of EVs is the lower residual value of EVs given rapid improvements in battery technology. Swapping protects fleets from this risk, as obsolete battery packs could be exchanged for newer ones. The capability to smart charge the batteries or provide grid services through the swapping station could also reduce the need for expensive electrical upgrades. Given the challenges with integrating with highly-proprietary battery systems, it seems most likely that swapping companies will see success in integrating with less proprietary and cutting-edge battery technologies, trading performance of an individual pack in exchange for fleet-wide uptime performance.
What do you think about automated charging? Are there other factors this article missed? Feel free to share your thoughts in the comments!
Note: At the time of writing this post, I work at Cruise on charging and energy infrastructure. This post relies solely on publicly available information and represents my own opinion only, not that of Cruise or any other organization.