Introduction to Electric Charging Station

Electric vehicle (EV) is one possible trend of future transportation. Instead of a gas tank, the EV use batteries as power supply. The running distance per charge of EV’s battery is about 100 mile. As a result, for a long distance drive, it is essential to charge EV batteries at public infrastructures. However, charging the batteries usually requires a long time. Battery switch station and DC fast charging station provide ways to overcome (in some levels) this drawback.

Battery switch stations (or battery swap stations) replace empty (or near empty) batteries with full-charged batteries to complete charging for EVs. By replacing EV’s batteries with full-charged batteries at the battery switch station, EVs can accomplish the process of recharging less than 2 minutes [1]. The capital cost of a battery switch station is $500,000 [2], nearly half the price of a typical gas station [3]. These battery switch stations are capable of swapping multiple battery types by removing and changing batteries from under the car. The video below is about how this process works [4]. The business model of EV is leasing batteries other than selling them. Transferring costs over the battery, battery life, maintenance and quality to the battery switch company [5], and hence reduce the capital cost for clients.

The main alternative technology for EV charging is DC fast charging (also referred as level 3 charging [5]). It is a nationwide infrastructure in the US, and has already been widely constructed. DC fast charging station works the way like a gas station. By plugging in with a standard connector, users can charge the car like fueling gasoline cars. The equipment (480 V) provides 50 kW to the batter and the charging time is 20 to 30 minutes [5]. Usually, we recharge battery to 80%~90% of its capacity, due to the saturation characteristic of charging a battery. The capital cost of a DC fast charging station is about $50,000 [5], much cheaper than that of a battery switch station. A disadvantage is the station can only serve limited number of cars at the same time. That means the expected delay time can be more than 30 minutes. Besides, DC fast chargers will degrade the battery and the damage is unrecoverable. In the recharge time, high power charger may also affect the quality of electric grid.

Based on the features introduced above, either one of the charge stations is not perfect. They both have their own advantages and disadvantages. The table below is a summary. In the table, BSS stands for battery switch station, and DCFCS stands for DC fast charging station.

BSS

DCFCS

Waiting Time (per full charge)

1~2 minutes

20~30 minutes

Construction Cost

$500,000

$50,000

Damage to Battery

Can be ignored

Yes

Serving Capacity

Can be unlimited

Limited

[1] Better Place. Wikipedia, The Free Encyclopedia. Wikimedia Foundation, Inc. 2004. 12 April 2012. (http://www.enotes.com/topic/Better_Place).

[2] Kate Galbraith. “Better Place Unveils Battery Swap Station”. New York Times. http://greeninc.blogs.nytimes.com/2009/05/13/better-place-unveils-battery-swap-station/. Retrieved 2009-10-05.

[3] Cornell, Clayton B. “Better Place Unveils First Solar-Powered Electric Vehicle Battery Switching Station : Gas 2.0”. Gas2.org. Retrieved 2009-10-17.

[4] http://www.youtube.com/watch?v=KKA4GhVn0a4

[5] Michael Webber. “Transportation II, slide 25 and 31”, Energy Policy and Technology 2012 spring class slides.

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2 Comments

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2 responses to “Introduction to Electric Charging Station

  1. rachelmarie88

    This was a very interesting and informative post. I was not aware of battery switching stations as a potential solution to electric charging stations. I agree that the short waiting time and negligible battery damage associated with a battery switching station are definitely big incentives that could give any battery recharge station a run for its money. However, like you mentioned the infrastructure investment needed to go into large scale implementation of battery switching stations is an order of magnitude greater than charging stations; furthermore, a recent article from Discovery News states that in order for switching stations to be a more secure investment, developers need to consider making the design of these stations flexible for updates and future improvements to electric car batteries [1]. A survey conducted by Accenture of more than 7,000 individuals in 13 countries found that 38% of consumers would choose to swap their car battery compared to the 62% that would prefer to recharge [2]. While 38% is impressive, it may not be enough to make the investment of battery switching stations cost-effective. In my opinion, I like the idea of battery switching stations. I think that there may be more security risks such as theft involved with battery switching than battery recharging, but I have not read anything that indicates such risks. Thanks for making me more informed!

    [1] Read, Richard. “Better Place Shows off Europe’s First Battery Switch Station.” Discovery News. N.p., 1 July 2011. Web. 3 May 2012. .
    [2] “Plug-in Electric Vehicles: Changing Perceptions, Hedging Bets.” Accenture. p. 26, 2011. Web. 3 May 2012. .

    • mranderson0416

      It is true that a disadvantage of electric vehicles is the charging time and lack of infrastructure for rapid charging. I don’t know what standardization has been applied for rapid charging, but I assume voltages, power levels, and electrical connectors are probably not standard across manufacturers- I think this will need to be addressed before wide-spread adoption or infrastructure build-out of rapid charging stations occurs. The issue I see with swap stations is degeneration of the batteries, which is no doubt partially coupled to how a car is driven- I think this will be a scaling challenge for the technology, because performance of the car now depends on the quality of the car and the battery, which depends on how the previous driver treated it [1].

      A possible solution would be triple-hybrid vehicles, where the “battery” is actually a combination of a conventional battery and a large capacitor. Capacitors have the advantage of extremely rapid charging rates, and this charge would slowly feed into the battery after the car leaves the station. Large capacitors are still under development, with only 5-10% of the energy density of lithium-ion batteries- however, their price continues to drop and their performance will likely increase [3].

      Ultracapacitors have started seeing service in buses [2] and some locomotives (they are useful for handling the current inrush when starting extremely large motors) but no hybrid passenger vehicles current use them, that I know of.

      Your post is interesting- I was unaware that switching stations had begun to appear.

      [1] – http://www.dailytech.com/Honda+Civic+Hybrids+Encounter+Battery+Life+Problems+Software+Update+Problematic+for+Some/article19357.htm

      [2] – http://www.technologyreview.com/energy/23754/?a=f

      [3] – http://www.technologyreview.com/energy/27045/

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