Electric Vehicle Charging Levels

There are two official charging levels for electric vehicles: level 1 and 2.  These charging levels are designated by SAE, the Society of Automotive Engineers, which applies to North America but can also be adopted worldwide.  In particular, SAE J1772 covers the conductive charge coupler for electric vehicles.




Why should I comply with the SAE J1772 standard on my EV conversion?


The main reason to comply with this standard on your charging connector is to allow for use of public charging stations.  As electric cars grow in popularity, the number of charging stations will increase.  All new electric vehicles from OEMs, Original Equipment Manufacturers, are using the J1772 standard.  It just makes sense to follow their lead and put that on an electric vehicle conversion.



Purpose of SAE J1772 Standard


This SAE standard defines the operation, function, and dimension requirements for electric vehicle inlet and mating connectors.  The standard was originally issued in 1996 and was updated in 2001 to include level 2 charging after the release of the GM EV1 which used an inductive charger coupling.  The last charging level addition was in 2009 which expanded level 2 into low and high current versions.




Charging Level 1


The lowest charging level is 120VAC with peak current at 16 amps, the single phase power is a typical setup for a house receptacle.  This does require that the receptacle is on its own dedicated circuit and breaker, and the peak power for charging would be 1.92 kW.




Charging Level 2


The highest charging level, under J1772 standard, has 240VAC.  The initial 2001 standard was 32 amps of peak current, which meant that the peak power was 7.68 kW.  With the latest revision to charging level 2, the peak current is now 80 amps with peak power at 19.2 kW.  Both of these are with a split phase and have a dedicated circuit and breaker similar to level 1.





As a side note, the wireless charging from plugless power provides the equivalent of level 2 charging.  Naturally, this is without the use of a J1772 connector.  The wireless charging installation does allow for use of connected charging when not charging wirelessly.  See Wireless Charging Electric Vehicles for more information.



Design and Function of J1772 Connector

One of the identifying features of the J1772 connector is the five pin design. There are three larger pins, two of them are AC lines and the other is a ground line. The two smaller pins are for proximity detection and control pilot lines.

A public safety concern for the level 2 charging stations is exposure to live wires in the connector when not inserted in the electric vehicle for charging.  In order to ensure that there will not be exposure to live wires of reasonably high voltage and current, is to always make the charging lines dead.  The receptacle on the electric vehicle has to create a specific resistance on the pilot line when the connector is inserted.  This will activate the main charging lines and start the charging process.  This method ensures that the connector is engaged in the electric vehicle and that the connector meets the SAE J1772 standard.  In the event that there is resistance on the ground pin, the circuit will open and kill the charging lines even if the connector is fully engaged in the receptacle.  This could be the result of two pins touching or corrosion.

Tesla Superchargers

There is level 3 charging which has not been standardized at this point in time. The Tesla supercharger stations that are expanding from coast to coast are level 3 charging. Due to the higher voltage and current than the standardized level 2, these are only able to be used with the Tesla Model S vehicles.



How do I comply with SAE J1772?


The charging receptacle installed on your electric vehicle will need to state that it meets SAE J1772-2009 or newer.  This will allow the use of public charging stations at the level 2 power for your electric vehicle conversion.  There should be a minimum of a level 1 charging station setup in your garage or driveway.





Here are a couple articles that you might like.

Wireless Charging for Electric Vehicles

Lithium Ion Battery Types for Electric Vehicles


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