What's the difference between ISO 15118 and DIN SPEC 70121 ?

The German technical specification DIN SPEC 70121 is based on an early, unpublished version of the ISO 15118 standard and defines digital communication between an electric vehicle and a DC charging station. DC stands for direct current, which means DIN SPEC 70121 covers only the DC charging mode whereas ISO 15118 covers both AC (alternating current) and DC charging modes.

The ISO 15118 series has evolved greatly since the first publication of DIN SPEC 70121 and this has lead to a host of technical differences between DIN SPEC 70121 and ISO 15118. DIN SPEC was first released in 2012 and updated in 2014, whereas the first version of the technical specification of ISO 15118 was released in 2014 and version 2 is on its way.

It’s like a dialect of the same language. If you don’t understand that dialect, then it doesn’t matter if it’s the same language or not: you can’t move forward with the conversation.

This means that a charging station that only supports ISO 15118 cannot charge an EV that only speaks DIN SPEC 70121. But if the EV is able to speak both dialects, then they can successfully enter a charging session – and vice versa. That’s where it becomes very important that you understand and apply this knowledge to your product line and future innovations.

Another key distinction between ISO 15118 and DIN SPEC 70121 is that the latter does not support Plug & Charge, meaning: no secured communication via Transport Layer Security (TLS), no digital certificates, and no XML-based digital signatures so authenticity and data integrity can’t be ensured. Also, no smart charging is possible via DIN SPEC 70121, meaning: you can't send charging schedules to the EV to make it charge in a smarter, more grid-friendly way.

DIN SPEC 70121 was created as an interim solution to get the market up and running until ISO 15118 was released. Unfortunately, it still prevails in various test installations at the ISO 15118 Testing Symposia (Video 1 of my course “Revolutionize Electric Vehicle Charging” has visuals from the most recent symposia). But DIN SPEC’s days are numbered, as ISO 15118 and its wide range of additional features fast become the industry standard.