Why and how to joyfully move our butts around town, without mucking the place up.

Best deployment of electric car charging stations for optimum driving flexibility

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Tags: EV Charging

Do we install a DC Fast Charging station on every street corner? That would be expensive because those stations are costly. There's a macro-economical budget for deploying electric car charging stations to promote a flexible electric car ownership experience, of when and where electric car owners drive their cars, and how far they can drive in a day.

Electric Vehicle Charging And Usage Scenarios goes over the typical usage patterns. An electric car owner can base their driving range on their home charging station, or base it on the trip between their home and office charging stations, or using charging stations scattered around town for opportunity charging. Additionally fast chargers can be located in critical spots to handle longer distance driving.

But what is the best sort of charging station for each location? How should the sum of all organizations utilize the budget for electric vehicle charging stations to build out the optimum charging station deployment pattern?

Best effort to summarize this is:

  • Typical driving needs of typical drivers are satisfiable by even the modest range of todays electric cars, especially if/when J1772 EVSE's are deployed around town.
  • Fast charging systems are expensive, are required for long range electric car travel, so therefore we can expect them to be deployed only at places critical for long range travel.

Where to install what kind of charging station

Source: Presentation by Mr. Anagawa of TEPCO given at Plug-In 2010

I've seen the same breakdown given in other presentations as this. On one axis is charging station cost, on the other axis is the required recharge time for various sorts of users.

In some scenarios we are not sensitive to the recharge time. For example, if we're at home, the car is plugged in recharging, and we're about to go to sleep for the night, we're unlikely to need the car for another 8 hours, and the recharge time can be really long. Hence this scenario can be satisfied with an inexpensive low cost charger. On the other hand if we're on a long trip, the need is for quick recharges along the highway, which requires an expensive charger.

Anagawa-san's analysis says Level 1 or Level 2 charging in public spaces is undesirable. The two likely scenarios are in the gold dashed circle. It breaks down as so:-

  • Home/Office: You're parked for hours at a time, so low speed charging is okay. This is best handled with an inexpensive power outlet or a slightly more expensive J1772 EVSE.
  • Along the highway on a long trip: Speed is of the essence, and you're not willing to wait hours for a recharge. High powered expensive charging stations are desirable.

However, in my mind if you're parking at a shopping center for a couple hours, Level 2 is quite suitable if a) you don't require a full recharge, b) your car isn't fully depleted. If your desire is to push the longest range the electric car can handle in a day, DC Fast Charge is required.

Typical daily driving needs

Source: Presentation by Mr. Anagawa of TEPCO given at Plug-In 2010

Most of us, most of the time, are just driving around town. The typical range of the typical electric car easily handles this, and Level 2 opportunity charges can help to make us feel comfortable. It's those occasional long range trips, right? This reinforces the point about the high power expensive chargers should be located at critical locations, primarily highways, and to deploy lower speed inexpensive chargers ubiquitously.

Suitable recharge times

First, Electric Vehicle Charging And Usage Scenarios gives us some typical locations for recharging and the typical time expectation at each:-

  • Home base - 10 hours or more overnight
  • Office - 8 hour work day
  • Church - 3 hours
  • Shopping - 2-3 hours (or less)
  • Visits to doctors and the like - 1 hour
  • Parking garages - depends on the trip, could be all day or several days if at an airport
  • Rest areas along highways - quick, fast, up to an hour for a meal

Electric vehicle charging station costs

The different kinds of electric vehicle charging stations (EVSE) have a wide range of costs. Some are a simple plug in the wall that might already exist, while others are large refrigerator sized boxes containing specialized equipment.

Part of the cost is the sort of electrical supply required for each type of electric car charging station. See SAE Electric Vehicle Charging Levels for details.

LevelElectrical SupplyCharger typeCostDiscussion
**AC Level 1** 120 volt AC at 12 amps is 1.4 kilowatts, at 16 amps is 1.9 kilowatts, etc. NEMA 5-15, 5-20 Cheap This rate is common in the U.S. but other countries have 240 volt circuits as the common power supply instead.
**AC Level 2** 240 volts AC, at power levels up to 80 amps, for 19.2 kilowatts maximum NEMA 6-20 and other 240 volt outlets, typically though this is handled through a J1772 EVSE $500-2000 This is a typical normal power circuit available in most homes, however the 80 amps level can be hard to come by in a normal home.
**AC Level 3** 240 volts, single phase or three-phase AC, at higher power levels unknown - The ABB Terra 53 supports 3 phase AC up to 43 kilowatts unknown The SAE committee hasn't specified charging equipment for this power level. However, both Smart and Renault are delivering cars with three phase AC 22 kilowatt and 43 kilowatt charging systems
**DC Level 1, 2, 3** Electrical service to the EVSE is probably three phase AC, at 480 volts, at really high amp rates CHADEMO and Tesla's Supercharger are the only existing system's, the SAE Combo Charging System has been standardized but no existing cars are on the market to use it $10,000 or more This is otherwise known as DC Fast Charge. See [EV Fast Charging, whether standardized or not](/ev-charging/range-confidence/chap8-tech/ev-dc-fast-charging-chademo-ccs-sae-combo-tesla-supercharger-etc.html) for details.
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