Innerworkings of EV Autocharge | Automatic authorization & start of electric vehicle charging with OCPP

Credits to : Open Fast charging Alliance (OFA) - consortium of leading fast charging operators in Europe, who formulated the AutoCharge mechanism, protocol schema and all the explanations of this article.

What is Electric Vehicle AutoCharge?

AutoCharge is a mechanism to authorize electrical vehicle for charging based on a vehicle identifier. For an EV driver it would be as simple as plugging in his/her car to charger and let charger to do authorization automatically to allow (or not) for charging to start. 

Below is the simple sequence of operation at EV driver's perspective:

1. A driver arrives at a charging station and plugs in.
2. Charging starts immediately and the driver can walk away .
3. The payment is processed in the background via his/her regular contract with the provider

How does AutoCharge work ?

Autocharge is technically very simple : The authorization works based on the charging station that reads something uniquely identifying the vehicle when the connector is plugged in. There is no agreement yet on a unified vehicle id, but a lot of cars have a MAC (Media Access Control) address assigned to it, just like any device connected to the Internet.

Above is a schema of Autocharge implementation based on OCPP (Open Charge Point Protocol) commands. Refer the below numbering with the above command sequence.

1. The driver connects his/her electric vehicle to the charging station by plugging in the charging cable.
2. The electric vehicle sends its MAC address to the charging station.
3. Charging station uses OCPP’s ‘Authorize request' to send the MAC address it received from the electric vehicle to the CSMS.
4. The CSMS will then read the MAC address from the received OCPP 'authorize request' and check if the MAC address matches a whitelist of electric vehicle’s MAC addresses.
5. If the read MAC address matches with CPO/EMP's approved whitelist --> then start charging.  • If not matching, the CSMS will store the MAC address and ‘reject’ the authorization.  Upon the reject message, the charging station shall indicate to the user that he/she needs to authorize the EV using one of the other available methods like RFID card or smartphone app, so that the user can use AutoCharge from next time. 

Below is how the first time authorization happens:

If a driver plugs in his vehicle for the first time, its vehicle ID might not be known by central system. In this case Vehicle ID should be stored by central system, so it can be associated with user account later:



As you see above, vehicle ID is stored by central system and in case of successful authorization via another method and successful charge session, charger operator could contact user to ask if he would like to associate vehicle ID with his account and enable AutoCharge for future charge sessions.

💡Note: OCPP protocol doesn’t have command which could provide linking of vehicle ID to existing user account, so it should be done via other communication channel, e.g. web application, phone application, by phone with service representative, etc.

How to stop charging with Autocharge

To stop a charge session initiated by AutoCharge any allowed method could be used as long as it is
supported and properly implemented in the Charge Point and Central System. For example: stop by a vehicle, remote stop by the user, local (Authorized or not, depending on settings and use case) stop by a user, etc.

How it works together with traditional authorization methods

There are 2 main authorization methods used at the moment in charging:

1. Via RFID card reader built in a charger
2. Remote authorization, when user is authorized via phone app, SMS code, QR code scanning, etc.
(in other words via different channel than charger communication channel).

In case of Autocharge there should be always another (primary or initial) authorization method, namely one of the above. If authorization is not successful via Vehicle ID, charger should not indicate that authorization is failed, but wait for another authorization method. Otherwise it would result in bad user experience: authorization failure message might be displayed every time driver plugs in connector into a car.

It is so simple, are there any drawbacks?

Autocharge is intended to be a simple and fast way to realize a very user friendly operation. Probably there will be some limitations going forward. At the moment Autocharge will only work with CCS based vehicles, however CHAdeMO could also easily include a vehicle ID or MAC address in the communication.

It is definitely more secure than RFID, because you couldn’t that easily copy or simulate MAC address while a RFID card is very easy to copy. Should any misuse happen then it may be detected after some time by the back-office of the operator, camera’s or driver reports and the access can be denied. The likelihood of this scenario probably does not outweigh the benefits of having a fast introduction of such a driver friendly feature.

AutoCharge is not same as ISO 15118 Plug & Charge (PnC)

Last but not the least: please note that the AutoCharge mechanism explained here is not same as ISO 15118 Plug & Charge (PnC).

Both AutoCharge and ISO 15118 Plug & Charge (PnC) offer the same user experience (charging process that starts as soon as the EV is plugged-in); however, the these two approaches differ drastically in their underlying security and complexity.

Fastned (The Netherlands), Sodetrel (France), Smatrics (Austria), Grønn Kontakt (Norway), and GOtthard FASTcharge (Switzerland) are some of the leading fast charging operators (in EU) who have implemented Autocharge. Some parts of Autocharge mechanism may also use ISO15118 for EV-EVSE communication; but is different from PnC.

Hope this article has got you a good start with the working principles of AutoCharge - Automatic charging start and authorization of electric vehicles. For more information and questions, please reach out via email / comment section.