Which is best for electric car charging? Level 1? Level 2? Fast charging?

This may seem like an obvious observation:  Ubiquitous fast charging will improve electric car adoption, and electric car utilization.

To me that’s a “DUH” sort of thing to say, but at the same time the U.S. planning for electric car charging is dominated by public level 2 charging stations.  Obviously the powers-that-be don’t grok the importance of public fast charging.  The relative lack of fast charging in the U.S. may be undermining the whole project of electric car adoption.  It may be that public level 2 charging itself harms the whole project of electric car adoption.

Here’s a picture that should help understand why.

TEPCO’s T. Anagawa
PlugIn 2010

This picture is attempting to demonstrate the scope of possible EV charging scenarios, and describing which sort of charging is preferable in which situation.  On one axis it shows the difference between charging in public versus “private” charging whether that is at home or at an office.  On the other axis is the difference between fast and slow charging.

Note that this chart was presented in July 2010, based on research in Japan dating back to 2008.

Level 1 charging great for both home and office use – could enable ubiquitous charging access

For private charging scenarios it’s preferable to have really slow charging, what’s called “level 1”.  Why?  It’s because “level 1” charging is simply the ubiquitous 120 volt 15 amp outlet that’s everywhere.  It is incredibly cheap to install, and could be present literally anywhere.

Level 1 charging is suitable for any scenario where the car will be parked anyway for many hours while the car’s owner is off doing X or Y or Z .. for example, sleeping.  Or working.  Does it matter to you how long the recharge takes if during that time you’re somewhere else doing things you’d normally be doing anyway?

Why is Level 1 charging preferable over Level 2 at a workplace?  It’s because of the relative cost of the charging station equipment.  The level 2 station can cost $2000 or more per station to install, while the level 1 station (a simple power outlet) would cost $1-200.  This huge cost difference is the difference between ubiquitous EV charging, and a handful of EV charging.  On the other hand, level 1 power outlets don’t have any accounting or access control capability, and the bean-counters may prefer level 2 stations because of those features.

Level 1 charging can also be great for home use, and I hear of electric car owners who do exactly this.  Rather than go through the complexity of getting a proper level 2 charging station installed at home, they just get a regular power outlet next to their parking space and use the level 1 charging cord that comes with the car.  If you arrive home at 6pm and won’t leave until 7am that’s over 12 hours of level 1 charging time, which is enough for quite a bit of driving.

A little bit of advice :-  If you’re going to depend on a regular power outlet for home charging, do one of two things.  It’s preferable that the power outlet is close enough to the parking space so you don’t use an extension cord.  If you must use an extension cord, get one that uses 10 gauge wires.  Why?  These are rated for higher amperage and will handle the charging current without overheating.  Also make sure that the power outlet you’re using is modern, and reliable.  You wouldn’t want to use a flaky power outlet running over inadequate wiring in the walls, risking starting a fire, would you?

Fast charging preferable to level 2 charging

At the other end of the spectrum is those scenarios where you’re “in public” and looking to charge.  For example running around town doing this and that, and stopping for a quick charge while out (“running errands”).  Or, taking a longer trip and stopping to refuel and stretch your legs every so often (“road trip”).

In either scenario you want the charging time to be as quick as possible.  With level 2 charging you’re forced to wait for 4 hours or 8 hours or more depending on the car.  This length of time doesn’t work for either the “running errands” or “road trip” scenarios.   Hence, level 2 charging is incompatible with public charging.

Yet, in the U.S., level 2 charging stations are being set up in shopping area parking lots.

What’s compatible with both the “running errands” and “road trip” scenarios?  Fast charging.  Why?  The idea is that within 20 minutes or so your car will gain a significant amount of range.  At 6 kilowatt level 2 charging, 20 minutes will give you about 10 miles of range.

If the fast charging station is next to a coffee shop, it’s easy to imagine the conversation going .. oh, the battery pack is running a bit low, let’s stop at the QuickieCharge for a Starbucks coffee and charge the car up.

That’s exactly why the Japanese called their fast charging system CHAdeMO – because it translates to “Have a sip of Tea”.

The current crop of fast charging isn’t quite suitable for the road trip scenario.  But, they are perfect for the running errands scenario.  Why?  It’s that at a CHAdeMO station you’re gaining about 50 miles range in a half hour of charging.  While this improves the usability of your electric car, it’s not quite enough for a proper road trip.  The car which can handle the proper road trip is the Tesla Model S, when recharged at a Supercharger.  In that case it can gain about 250-300 miles of range in an hour.  While that’s phenomenal for electric cars, it’s not quite fast enough for the hard core road tripper.

I’ve written up more about this, including some estimates on costs, here:  Why is Fast Charging required for widespread electric vehicle adoption 

A couple recent related posts are:

CHAdeMO and SAE DC Fast Charging adoption possibilities – EV adoption prospects are hanging in the balance

Are electric cars with small battery packs and fast charging a great combination for EV adoption?

About David Herron

David Herron is a writer and software engineer living in Silicon Valley. He primarily writes about electric vehicles, clean energy systems, climate change, peak oil and related issues. When not writing he indulges in software projects and is sometimes employed as a software engineer. David has written for sites like PlugInCars and TorqueNews, and worked for companies like Sun Microsystems and Yahoo.

About David Herron

David Herron is a writer and software engineer living in Silicon Valley. He primarily writes about electric vehicles, clean energy systems, climate change, peak oil and related issues. When not writing he indulges in software projects and is sometimes employed as a software engineer. David has written for sites like PlugInCars and TorqueNews, and worked for companies like Sun Microsystems and Yahoo.

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