If the goal is driving electric cars anywhere we go, what's the best implementation? We've suggested that DC fast charging is the best tool to support long range electric car travel. The 1 hour or so recharge time is a huge improvement over regular AC Level 2 at 6 kiloWatts. On the other hand, most people are accustomed to gasoline cars, and desire to replicate the 300+ mile range 5 minute refueling experience.
That's where the battery swapping idea comes into play. A battery swapping facility, with fully charged battery packs on-hand and a robotic battery swapping machine, can replace a depleted battery pack with a fully charged pack in a couple minutes. Functionally speaking that makes for a compelling story, but as we'll see in a minute the reality doesn't fulfill the dream.
This isn't a theory, since at least three times the idea has been implemented and used by the public.
That past experience gives us these lessons:
- Presupposes that battery prices will remain expensive
- Robotic battery swapping stations are far more expensive to install than fast charging stations
- Tends to require a leased battery pack, which has proved to be controversial
- Tends to force standardization of battery pack size and shape
- Tends to limit migration to new battery chemistries as they're developed
The key combination is that if battery pack prices remain expensive, customers will shy away from buying the battery pack outright, will prefer to lease the battery pack, and would appreciate a service to exchange battery packs. The reality is that battery pack prices have fallen more quickly than expected, as demonstrated by the new wave of 200+ mile range electric cars priced at $35,000 MSRP. Hitting that price point requires a cheaper battery pack. As battery prices fall the electric car price premium shrinks, making cost less of an issue, reducing the incentive to offer battery leasing.
There have been two electric cars offered with a leased battery pack. One, the Renault Fluence, was built for sale through Better Place, and is no longer available now that Better Place has gone out of business. The other, the Renault Zoe, was originally to be offered with a battery swapping service, but Renault instead launched that car with AC Fast Charging. The latest version of the Zoe, with a much larger battery pack, can now be purchased with the battery pack bundled into the price, whereas the previous version required a battery lease. Zoe customers were never happy with the lease arrangement, while otherwise the Zoe is the most popular electric car in Europe.
Expense is an important issue because of the total cost to build a useful charging network. For a given budget, a network with lower cost stations will have more sites than a network with high cost stations. Hence, an expensive-to-build network will tend to expand slower, and be more difficult to run as a profitable business.
While battery swapping doesn't seem useful for use by the general public, it may be useful in a closed network situation. For example, delivery or taxi services need their vehicles on the road earning money, not sitting at a charging station. Drivers could return to a depot to swap battery packs and quickly get back on the road.
In a few years several companies plan to offer robotic autonomous vehicles as taxi's or delivery vehicles. Those vehicles need a fully automated recharging mechanism, and also need their vehicles to be on the road earning revenue. A battery swap station might be the ticket.
Electric Carriage and Wagon Company, 1900ish
In the earliest days of the automobile, gasoline was not the king. Electricity was. One of the early electric car makers, the Electric Carriage and Wagon Company, focused on electric taxicabs and also rented electric cars to the public.
In Manhattan the company had a fleet of a few dozen electric taxicabs. One achievement of the company came in the Winter of 1898 when massive snowstorms paralyzed New York City. Electric Carriage and Wagon's taxicabs arranged permission to drive on the sidewalks, and were able to offer service all through the winter when all other services were unable to move.
The company also had a technological achievement in regards to its centralized battery charging station. According to Edwin Black's book, Internal Combustion, the company had a central garage staffed by a crew of six workers. Using "specially constructed garage cranes, slightly elevated auto rails, and removable vehicle trays, batteries could be swapped out by a single mechanic in just seventy-five seconds." Batteries were moved overnight into a recharging room, ready to be used the next morning.
Seventy-five seconds of manual labor and the taxicab would be back on the road. A taxi service would be an important target market since the vehicle must spend the maximum time possible on the road earning fares.
Founded by Shai Agassi, the company sought to quicken adoption of electric vehicles by providing battery pack leasing services coupled with fast battery pack swap stations. Agassi's key observation was that battery packs are expensive, and therefore the cost would make people shy away from buying the car outright. Instead, offering a battery leasing would lower the cost making electric vehicle purchase more attractive.
According to some sources (Wikipedia) the battery exchange required 3 minutes. However, this demonstration video ( https://www.youtube.com/watch?v=qd0WPw3p2MQ) shows a battery exchange in 1 minute 15 seconds. Or about the time required by manual labor in 1898.
The company took on well over $1 billion in investment, developing a software system to run the business, as well as custom robotic battery exchange stations. The service launched in Israel and Denmark, at significant levels, and in a few other locations as pilot projects. For what it's worth, some of these pilot projects were taxi systems.
By mid-late-2012 the company was on the ropes, with Shai Agassi having been fired, and the replacement CEO fired in January 2013. Attempts to restructure the business failed, and by the end of 2013 the company had completely shut down with assets sold off for pennies on the dollar.
In late 2012, an Israeli press report said each Better Place station cost in the range of NIS 750,000-1.1 million. By the exchange rate at that time, it equated to about US $280,000. http://www.globes.co.il/en/article-1000802153 By contrast, fast charging stations cost well under $50,000 apiece.
While Tesla is famous for its Supercharger fast charging network, the company also developed a battery exchange system. This system had been in Tesla's plans from the earliest days of the company, for example it was discussed in Tesla's pre-IPO filings with the US Securities and Exchange Commission.
In the due course of time, June 2013, Tesla Motors demonstrated their battery swapping technology ( https://www.youtube.com/watch?v=S0-sHtlCZ7M). They did a head-head comparison of refueling a gasoline car versus a Tesla Model S battery exchange. Each battery exchange took 90 seconds, and they completed two within the time required to refuel the gasoline car.
As impressive as that was, the service was not commercially successful. They installed one swapping station between San Francisco and Los Angeles, making it available to their customers. Apparently very few availed them of the service, and eventually Tesla quietly shut it down.
One flaw was that because Model S/X battery packs are owned as part of the car purchase, the customer had to return to the battery swapping station to retrieve their battery pack. That made it very different from the Better Place offering because the battery pack lease meant the customer had no ownership role over one battery pack or another, and instead was leasing the right to use battery packs from the available pool. By owning the battery pack, a Tesla automobile owner is responsible for that battery pack, and had to retrieve it.