Introduction 

ChargePilot is a hardware neutral Charging and Load Management System for EV charging infrastructure. It distributes the power between several connectors considering, physical boundaries (fuses, capabilities, etc.), regulative boundaries (phase asymmetry, grid connection, etc.), economical boundaries (peak loading, low tariff regimes, etc.) and E-Mobility needs (departure time, SoC, etc.). Therefore, ChargePilot uses a local controller device called Smart Charging Controller (SCC), which is connected to the charge points via OCPP 1.6J and to the TMH Cloud backend via a proprietary, TLS encrypted connection. The following schematic shows how ChargePilot is connected to the charge points and to a third-party CSMS using OCPP 1.6J.

Connectivity Setup 

The SCC is connected directly to the Charging Stations via a local ethernet connection. All Charging Station have ChargePilot configured as CSMS. ChargePilot default OCPP back-end url: ws://172.22.0.1:9000

ChargePilot uses one internet connection to connect to the TMH Cloud and to the 3rd party CSMS. This connection can be established via Ethernet or via GSM with an additional router. So Charging Stations do not require to be connected to the internet (i.g. need their own SIM card for cellular connectivity).

Messages

The OCPP proxy forwards all allowed messages (see table below) initiated by the 3rd Party CSMS or by the Charging Station without any changes to the Charging Station or respectively to the 3rd Party CSMS. The 3rd Party CSMS will not see any difference within the messages to a direct connection to a charging station. Even vendor specific changes in the OCPP protocol will be forwarded without being touched. ChargePilot does not "normalize" or alter any messages.
This also applies to all signed meter values according to German "Eichrecht". The proxy has no influence on the Eichrechts-confirmity.

Handling of OCPP Messages

The following Profiles of OCPP1.6 are supported by the proxy

Messages Initiated by Charging Station

Messages Initiated by Third Party

Handling of Configuration

Configuration keys, which are supported by the charging station, can be changed using the ChangeConfiguration Message. The default value for the key MeterValueSampleInterval is 300s. The max limit and default value for the HeartbeatInterval is 300s. Higher values will be limited accordingly.
However, the following keys cannot be changed: MeterValueSampleData

Encryption

The following section shall describe the measures to secure the connection between ChargePilot's local Smart Charging Controller and an OCPP 1.6J based Charging Station Management System (CSMS). The proposal is based on the "Improved security for OCPP 1.6-J, Edition 2" published by OCA.

TLS with Basic Authentication

In principle, the SCC mimics the behavior of the charge point descripted in the "Improved security for OCPP 1.6J, chapter 2.4" of the OCA whitepaper. The charge points authenticate themselves using HTTP Basic Authentication. The CSMS authenticates itself using a TLS server certificate.

The username shall be equal to the Charge Point identity. The CSMS vendor shall provide a password for each charge point in a secure way. TMH will configure the SCC using their administration application. The CSMS can update the password using the AuthorizationKey in the configuration. In case of connection loss, the last known credentials will used. All defined errors described by OCA are implemented as described. In the current version, an Update of the AuthorizationKey cannot be performed.

Offline States

In the following table, the offline behavior in case of a connection loss is documented.