TagID code type

TagID code is used for three types of messages in OCPP:

  • Authorize
  • StartTrans
  • StopTrans

Format of TagID is not specifically defined, it is only noted that it needs to be a string. At least two vendors are using only HEX format. These are Alfen/ICU and DBT. Alfen/ICU is using 7 byte HEX TagID and DBT is using 4 byte TagID.

There problem is especially apparent on DBT equipment as there are many RFID cards with 7 byte code that consequently fail to authorize on DBT charging stations.

In our case, mobile identification is composed using word »Mobile« followed by 6 digits, eg. Mobile000001. This TagID is not in hex format. Converting it to hex is not the best solution (especially for 7 byte hex), as we would soon experience the problem of code being converted to 7 byte hex code that is not unique. Array of 7 byte hex code is much smaller in comparison to the TagID we use, which would mean that the session could be assigned to the wrong user or to two users.

Same problem can occur while in roaming mode. In that case TagID, is even longer than our mobile authentication ID. Examples using the EVCOIDType:

  • DE-8EO-CAet5e4XY-3
  • DE*8EO*Aet5e4*3

Consequently, charging stations from mentioned vendors are unable to recognize the TagID. Here the problem with conversion is even greater, as the number of users is larger and will increase rapidly over the next years, meaning that the 7 byte hex code will surely not be the correct future-proof solution.

The only long-term solution we see and recommend is to put pressure to such vendors to change their TagID. They will experience problems sooner rather than later using such limited TagID codes.