What Is EVSE And Why Does Your Electric Car Charger Need It?

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2011 Chevrolet Volt 240V charging station

2011 Chevrolet Volt 240V charging station

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There was a time when an electric car could be plugged into just about any electrical outlet  its owner could find. With a little bit of ingenuity and forward planning, any electric car could plug-in just about anywhere.

We’ve heard stories of National Electric Drag Racing Association (NEDRA) Members plugging into 240V, 50A industrial outlets at the drag strip to obtain fast charging, Toyota RAV4 EV owners buying special chargers to enable the ageing electric cars a chance to plug in at J1772 charging stations and even of enterprising Tesla owners who carry just about every conceivable electrical converter to enable them to charge at anything from 110V, 15A to 240V,  70A.

But while drivers of existing electric cars just need to find an electrical outlet that matches the plug on the end of their charging lead, a new charging standard brings a little more sophistication to the mix, in the form of the Electric Vehicle Supply Equipment (EVSE) control.

Coulomb Technologies CT-500 electric vehicle charging station

Coulomb Technologies CT-500 electric vehicle charging station

What is EVSE? And why does your electric car need it? 

Simply put, EVSE is a protocol to help keep you and your electric car safe while charging. 

Using two-way communication between the charger and car, the correct charging current is set based on the maximum current the charger can provide as well as the maximum current the car can receive.

As part of the protocol, a safety lock-out exists, preventing current from flowing when the charger is not connected to the car.  It ensures that if a cable is not correctly inserted, power will not flow through it.

EVSE can also detect hardware faults, disconnecting the power and preventing battery damage, electrical shorts or worse still, fire.  

No User Input Necessary

There was a time when electric vehicle owners seeking ultimate connectivity and charging at the highest possible rate would have to manually adjust their car’s charger to ensure that only the charger did not pull more power than the circuit the car was charging from. 

While Tesla’s 2011 Roadster may have a semi-intelligent system using GPS to remember which charging limits are required where, owners still have to enter applicable current limits when charging takes place in a new location for the first time if the charging location can supply less than the charger cable can pull.

EVSE eliminates all user interaction beyond plugging the J1772 connector in. The charger takes care of the rest. 

charging cord for 2012 Ford Focus Electric

charging cord for 2012 Ford Focus Electric

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Can You Charge Without It?

While cars with the J1772 charger receptacle like the 2011 Nissan Leaf and 2011 Chevy Volt will allow you to charge using level 2, 240V chargers, you can also charge at a lower rate using a 110V, 15A supply.

Such charge cables may look little more than a dumb plug designed to enable emergency charging from a 110V domestic outlet, but the cables contain simple electronic circuitry to ensure the car does not draw more than the 110V 15A allowed from a domestic socket. 

What it doesn’t allow, however, is for a larger capacity plug such as a drier plug to be installed. Do that, and your electric car will likely fail to charge at all. 

Nissan LEAF Charging Port

Nissan LEAF Charging Port

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Conversion Boxes.

Over the next few years, expect some enterprising individuals to develop charger conversion boxes which enable an electric car to make use of any power outlet by spoofing the EVSE chargers to enable the user to charge from locations where electric car chargers are not yet in use. 

Expect the opposite too, as electric cars without J1772 receptacles seek to charge at any available Level 2, EVSE compliant charging stations. 

Simplicity Through Complexity

While some electric vehicle owners may view EVSE equipped chargers as expensive and unnecessary, they represent a much simpler way for the majority of consumers to charge their electric car. 

The safety features alone also prevent unauthorised access to electric vehicle charging stations to non electric-car uses, ensuring electric car charging points are quick, easy and safe to use for everyone. 

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Comments (14)
  1. The other thing is that EVSE is a standard. The SAE J-1772 standard means that all EVs built will have a common plug inlet. In the late 90's/early 00's there were several different plugs. The RAV4 used an induction paddle which was different than the GM EV-1 induction paddle which was different than the Avcon conductive paddle. So someone who wanted to provide power for an EV could conceivable have to put in several different EVSE units to support vehicles. Now you know that if you buy and install one, it will support everybody.
    Also the National Electrical Code (NEC 625) addresses the requirement for plugging in electrical vehicles safely which means there is no power to the plug until it's plugged in (as mentioned in the article). So all those different 220V outlets that are available (such as at camping grounds, race tracks, hardware stores, etc) are out of compliance because the sockets are always live. Not to mention there are over a dozen different 220V plugs.
    Also just to clarify, the EVSE is not part of the car, it is the box that connects power to the car. So there isn't really any such thing as an EVSE equipped car - unless somebody puts one in their car and carries around a bunch of 220V power cables (like the Tesla owner) so they can have Level 2 charging.
    So just to be clear - charger is in the car, not on the wall. EVSE is on the wall, not in the car.

  2. I like Nikki's artical's and find them informative but this one has a few issues from a technical perspective.

  3. Thanks guys - Sorry for the confusion. Of course, I'd meant that cars with the J1772 receptacle talked to the EVSE in the charger to ensure correct charging occured.
    Obviously not explaining things well today!

  4. I wish everyone would start calling them EVSE instead of "wall chargers" like you frequently hear. As stated above the chargers are built into the cars and the EVSE really just allows the car to be charged safely. EV newbies are often confused and think the EVSE is what charges the car and it really only provides the electricity safely. You could plug the cars right into a 220v outlet if you had a cable with a j1772 plug on the end, but it wouldn't be safe.

  5. The EVSE represents about $4 of technical value. It is a fancy ground fault outlet for your car.
    The real problem is that it has become so ghastly expensive. Why? Because it represents the friction point between SAE, UL, City Planning, Utilities, Contractors, and Manufacturers fiefdoms. All of these entities see your car as an appliance, and so, expect to be paid to “Certify” it. The EVSE has become the vehicle for all of those gatekeeper’s “Fees”. And, J1772 doesn’t address L3 connectivity.
    A successful paradigm for power connection already exists in the RV and Boating communities. They have connected to “Shore Power” successfully for years. (Note; the cable always belongs to the vehicle, not the site). Why did we need to start over?
    Reality? It is an over-compicated, botched attempt at standardization that won’t go away. Too bad.

  6. I have to heartily agree. It seems like everything the EVSE does, the car's own charger and intel could do. What makes this thing so freaking magical and heroic? Seems like a useless peripheral that needs to be integrated into the motherboard, to use computer lingo.

    Tesla agrees. They simply put all the fault tolerance in the on board charger itself. On their website, they list a basic 240V outlet and their own wall charger as being equal options. So why anyone would get the wall charger...I dunno. I suppose Tesla sells a few and makes some money off of suckers.

  7. Well, I learned something today. I knew it wasn't a "charger" on the garage wall, but didn't know exactly what it was. So it is like a GFI for your EV (technically inaccurate I know).
    John C. Briggs

  8. I agree with KeiJidosha. NEMA 14-50 outlets are safe enough for electric stoves and RV lots, as well as the 50 amp twist locks you find at RV parks. And the $4 technical value does not justify the thousands of dollar price tags these glorified extension cords with GFCI are bringing. And just so EVeryone is truthfully aware, SAE-J1772 as well as NEC codes are only "recommended" standards. A car company could just as well put that 50 amp twist lock on their car which means you'd be looking around for all the RV parks that allow you to camp by the hour ;-). NEC says the "charger should be hard mounted to the wall or floor". But if the charger is inside the car, its just another appliance. Plug it into that Range outlet in your home.

  9. What happens (very roughly) behind the scenes is this.
    1. The outlet or cable has no power connected to it
    2. You plug in
    3. based on either some resistors in the plug or a more complex communication system, the car and supply see something is connected and its limits
    4. it switches between 110 and 240 supply based on what the in car charger can take.
    5. a circuit breaker, similar to what you have at home has it current limit set, based on what the *cabling* can take (not what the in-car charger needs, that's their problem)
    6. the car immobilises itself, so you don't drive off with a cable attached
    7. the power is connected.
    The exact details will vary from car to car and "charger" to "charger" and I've purposefully excluded the billing mechanism for simplicity.

  10. Per NEC does EVSE require a separate disconnecting means?

  11. The NEC says so, within line of site, and lockable. I'm fairly new to the game, as most are, including electrical inspectors. It seems to vary region to region, and need to be consulted before an installation. I wonder if that may be throwing a red flag on an inspection, if they really require it? I don't know but I'd sure like to. I try to do my installations as least expensive as possible. A disconnect is expense (and unsightly to the public). But I see many installs without. How could that be??

    Another question in my mind is about copper verses aluminum. It appears many EVSE are rated for copper only (or their components such as the contactor). It would be much cheaper to use aluminum (appropriatley sized). Is there something.

  12. What are the best EV conversion kits for Fiat 127?

  13. Any reason these EVSE are $700 to $1000? Any idea where to buy them at a better price?

  14. What does an EVSE do that THE CAR ITSELF COULD NOT BE MADE TO DO AT THE FACTORY? Why do I have to pay for this, this thing, this useless peripheral that should be integrated?

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