Range Confidence: Charge Fast, Drive Far, with your Electric Car

By David Herron

Charging levels - Level 1, Level 2, DC Fast Charging, etc

Proper terminology usage may seem boring. Improper terminology usage can lead to arguments, misunderstanding, and in some cases wars. Therefore it's useful to use the correct terms so we understand what each other is saying when we talk about electric car charging.

Typical phrases I hear among electric car drivers is:

  • Level 2: Typical 240 volt AC charging stations.
  • Portable Level 2: A 6 kiloWatt AC charging station set up to be carried along.
  • Level 1: The typical line-cord charger sold with the car.
  • DCFC, DCQC, Level 3: These variants refer to DC fast charging stations, whether CHAdeMO, Combo Charging System or Tesla's Supercharger.

These are useful, they're what many of us say in informal conversation, but this isn't the correct terminology.

SAE's "Level 1/2/3" Terminology

The Society of Automotive Engineers (SAE) is a standards agency overseeing the Automotive Industry. For electric car charging, the SAE convened a committee called "J1772". You may have heard of the "J1772 plug", which some call a "J-Plug", so now you know where the name came from. One thing the J1772 committee developed is this terminology table

AC Charging Systems DC Charging Systems
AC Level 1: 120 volt single phase AC up to 16 amps, for up to 1.9 kiloWatt charge rate. Typically this is limited to 12 amps. DC Level 1: 200-450 volts DC up to 36 kiloWatts (80A)
AC Level 2: 240 volt single phase AC up to 80 amps, for up to 19.2 kiloWatt charge rate. Typically this is 32 amps. DC Level 2: 200-450 volts DC up to 90 kiloWatts (200A)
AC Level 3: More than Level 2. A couple car makers make cars supporting three phase AC charging at rates up to 43 kiloWatts. DC Level 3: 200-600 volts DC up to 240 kiloWatts (400A)

In AC charging systems, the car has an on-board charger does AC to DC conversion. In DC charging systems, there is instead an off-board AC to DC converter for the AC-DC conversion, and there's a direct connection to battery pack bypassing the on-board AC charging system.

This terminology was developed by engineers for talking among engineers. They need this sort of precision. The rest of us don't, really. The phrases above are fairly good, except we do need to distinguish between AC Fast Charging and DC Fast Charging.

IEC 62196 - Europe's terminology

The European standards-setters gave us a similar-but-different set of terms

  • Mode 1 - slow charging from a household-type socket-outlet
  • Mode 2 - slow charging from a household-type socket-outlet with an in-cable protection device
  • Mode 3 - slow or fast charging using a specific EV socket-outlet with control and protection function installed
  • Mode 4 - fast charging using an external charger

These correspond very well with the commonly used phrases listed above.

How should we use these terms?

The terminology above is what the Society of Automotive Engineers decided, and it's a nice precise system useful in discussion between engineering organizations. For us, the people in the street chatting informally, what's the best phrasing to use?

Let me offer these phrases that are already close to common usage.

Phrases Discussion
Level 1 or Trickle Charger or Opportunity Charger These describe the line-cord charger that's sold with plug-in electric cars. These phrases are commonly used, and are very descriptive.
Level 2 or Normal Charging Describes the typical AC 240 volt charging station that, as of December 2015, typically support up to 6 kiloWatt charging. These phrases are commonly used, and are very descriptive.
DC Fast Charge (DCFC) or DC Quick Charge (DCQC) or Supercharger Describes the fast charging stations. "Supercharger", since it's a Tesla Motors Trademark, should of course be limited to their infrastructure. These phrases are commonly used, as are the abbreviations, and are very descriptive.
AC Fast Charge In Europe there are two cars directly supporting three phase AC fast charging. This phrase is very descriptive of, well, an AC fast charging system. It should be used for any system supporting AC charging above 20 kiloWatts.

Notice that I'm not suggesting the Level 3 phrase in any of these. Currently usage of the Level 3 phrase refers to DC Fast Charge systems. However, I find Level 3 imprecise and causing confusion.

We have potential confusion in a couple years when 100 kiloWatt CHAdeMO and Combo Charging System stations are available. [LTP1] [LTP2] Such systems are in development, and in some cases demonstrated. The 100+ kiloWatt charging rate becomes very important for 200+ mile range electric cars. What do we call 100+ kiloWatt CHAdeMO and CCS?

We have a convenient brand from Tesla Motors for their charging stations - Supercharger. There won't be such a convenient brand for CHAdeMO or CCS.

Maybe we can use the same phrase, "DC Fast Charge", to describe both 50 and 100+ kiloWatt DC fast charging systems? Maybe doing so will instead create confusion? The SAE committee says the first is DC Level 2, and the second DC Level 3, FWIW.

The practical difference between 50 kiloWatt (150 miles of range per hour of charging) and 100+ kiloWatt charging (300 miles of range per hour of charging) suggests there should be a different phrase. But nothing immediately pops into mind to build on the existing phrases.


Range Confidence is Copyright © 2016-17 by David Herron

Charging levels - Level 1, Level 2, DC Fast Charging, etc

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