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Charging Communication

DIN 70121: CCS DC charging early communication standard

DIN 70121 is a CCS DC charging communication standard formulated by Germany's DIN. It was released before ISO 15118-2 and was widely deployed in early European and American DC fast charging piles.This article summarizes the protocol structure, message flow, and compatibility of ISO 15118-2 of DIN 70121, as well as the scope of support of KopherBit EVCC for DIN 70121.

Summary

DIN 70121 is a CCS DC fast charging communication standard formulated by Germany’s DIN. It came out earlier than ISO 15118-2 and was widely deployed in early European and American DC fast charging networks.DIN 70121 only covers DC charging, does not support PnC, does not force TLS, and the message set is a subset of ISO 15118-2.In order to be compatible with the existing DIN 70121 charging pile, KopherBit EVCC supports both DIN 70121 and ISO 15118-2 / -20, which is dynamically switched by EVCC in the ServiceDiscovery stage according to the version announced by SECC.

Technical Role

DIN 70121 is the early communication basis for CCS Combo (Type 1 / Type 2) DC charging and has the following characteristics:

  • DC process only; no AC charging sequence.
  • No support for PnC, only EIM authentication (external RFID/App).
  • No forced TLS, most implementations are clear text.
  • The message set is a reduced subset of ISO 15118-2, with a similar state machine but fewer fields.
  • Still establishing connections with SLAC and SDP through PLC (HomePlug Green PHY).

DIN 70121 is usually used as the fallback of ISO 15118-2: When either EV or EVSE does not support ISO 15118-2, both parties negotiate to downgrade to DIN 70121 to complete charging.EV side EVCC implements both and chooses according to SECC announcement.

Architecture

SubsystemRole
HomePlug Green PHYPLC physical layer, shared with ISO 15118.
IPv6 / DHCP / SDPGet SECC endpoint.
TCPTransport layer, no TLS.
V2G TP / EXIMessage serialization and efficient encoding.
State MachineDIN 70121 DC charging state machine.
BMS InterfaceInterfaces with the vehicle BMS to provide target voltage/current and limiting conditions.

Key Capabilities

  • DC charging complete process: SessionSetup → ServiceDiscovery → ServiceDetail → PaymentServiceSelection → ChargeParameterDiscovery → CableCheck → PreCharge → PowerDelivery → CurrentDemand → WeldingDetection → SessionStop.
  • Share PLC, SDP, EXI, and message packet formats with ISO 15118-2 to facilitate simultaneous implementation of the same EVCC.
  • EIM certification, following the existing charging network RFID/App process.
  • Widely deployed in early CCS DC fast charging networks in Europe, the United States, and Asia.

Engineering Inputs Required

InputPurpose
BMS Signal MatrixSoC, target voltage/current, maximum allowed voltage/current, temperature.
Vehicle CAN signalSignal definition between EVCC and BMS and VCU.
Charging HardwareCCS Type 1 / Type 2 Connectors and PLC Modules.
Interoperability testing requirementsEVSE brands and market regions expected to be supported (Europe, North America, China).

How KopherBit Supports This

  • EVCC software stack: KopherV2G provides DIN 70121 complete DC charging state machine, sharing PLC, SDP, EXI sub-modules with ISO 15118-2 / -20.
  • Dynamic switching: EVCC automatically selects the protocol according to the version announced by SECC during the ServiceDiscovery stage without resetting.
  • Verification: KCU Gen2 Testbench provides DIN 70121 and ISO 15118-2 interoperability testing.

FAQ

DIN 70121 Still need support?

Support is still recommended.Many early DC fast charging piles only implemented DIN 70121, especially the early CCS deployments in Europe and the United States.EV also supports DIN 70121 + ISO 15118-2 to cover a wider charging network.

DIN 70121 Does PnC support?

Not supported.PnC is only defined in ISO 15118-2/-20.DIN 70121 EIM certified only.

DIN 70121 Is it encrypted?

The communication itself does not enforce TLS, most implementations are clear text.If encryption is required, upgrade to ISO 15118-2 PnC or EIM-with-TLS path.

Differences from GB/T 27930 (China National Standard)?

GB/T 27930 is China’s GB/T DC charging communication standard. It uses CAN instead of PLC and is incompatible with the DIN 70121 / ISO 15118 series.The Chinese market requires independent stacking.

Will DIN 70121 be completely replaced by ISO 15118-2?

It will be replaced by ISO 15118-2 / -20 in the long term, but the existing DIN 70121 charging pile will still operate for many years.EVCC It is industry standard practice to implement both.

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