Hello blackburnite,
Kind of late answer, but anyways:
I reasonably familiar with the ISO 15118 standard. The standard uses dual layers communication:
- A low level basic communication that is specific for charging plugs (well basically all of them out there except Tesla, CHAdeMO and GB/T), this is described in detail by IEC 61851-1. There are two pins that are reffered to PE (GND), called proximity pilot (PP) and control pilot (CP). PP is just a 5V reference voltage and resistor divider (the when the connector is inserted the value of the resistance drops). The CP has some circuitry on both sides involved and is basically a 1 kHz PWM signal (although for ISO 15118, you have a fixed 5% duty cycle, PWM is not used) that switches between -12V and +3V, +6V, +9V or +12V (depending on the "state").
- For ISO 15118, a high level communication (HLC) signal is supperposed onto the CP low level communication making use of "powerline communication" (PLC). The name PLC is actually not well chosen here because the CP is not a "powerline", but the name is inherited from the underlying technology (HomePlug power-line). The high frequency (somwhere in the range from 3 MHz to 30 MHz, there are some channels) carrier is superposed on the CP line.
It would be a challenging project to build an "interpreter" for yourself, but who I am to decide what you spend your time on...
- For the basic communication, you have a lot of option: you can make a simple breadboard or a PCB with the circuitry on it (I can't give you the standard, but you can probably find the schematics online). You will have to decide though whether you want to be the "charging station", the "EV" or just a "listner" to the communication. The latter would be fairly simple: you just need an input that can sample the higher value of the PWM (which is either +12V, +9V, +6V or +3V) and "know" whether the PWM is "active" (in the case of ISO 15118, the duty cycle would either be 5% or 100%). You would come a long way with some resistors and diodes (be carefull though not to affect the signal). Even the most basic DAQ would probably suffices.
- For the high level communication: this is more challenging... Worldwide there are only two companies that make the PLC chips that are used in charging stations and EV's. The PLC version that they implement is called Green PHY (which is, as said, derived from HomePlug). One of these companies is Qualcomm. However, I can't promise this, the Green PHY standard might be close enough to the HomePlug standard, such that you might be able to use a classic HomePlug device (plenty of them in the stores). You would have to solve the problem of the AC though: the HomePlug expects 230Vac (or whatever you have in your region) while the voltages on the CP line are -12V/+12V, probably not enough to power the HomePlug device and putting 230V on the CP line will certainly destroy whatever is connect to it. You could either open up a HomePlug device and find the coupling capacitor, remove it and replace it with one that is coupled with the CP line or you will have to power it with AC and somehow decouple that from the CP line. Some capacitors and what not will get the job done.
If you have all this done, the fun only starts: the ISO 15118 is a quite complicated multilayered protocol:
- It uses IPv6 (not the classic IPv4) which, on its own, is already pretty complex).
- Depending on the use case and the charging station the data might be TLS encrypted, good luck with that 🙂
- The charging station and EV exchange EXI (sort of compressed binary XML) files that you will need to decompress and interprete.
- There are a lot of variables that are or can be exchanged. However, most of them are quite straightforward, but you will have to work your way in (dependig on the use case of what you want to do with it).
If you need any more help or advice, let me know. But don't say I didn't warn you 🙂
I guess that you could also try to get your hands on a gateway that is used in either charging station or EV's. But even if you would actually manage to find it (there are not a lot of companies making or selling those), you could only use them as a they are intended: as charging station gateway or as EV gateway, not to "listen in". That being said, there are some 'CCS listeners' on the market with which you can do just that. There is one of Vector and you might want to look into scienlab / keysight. However, these things are expensive and the licenses you'd need are even more expensive (altough you might circumvent some of the licenses to go hardcore and do it all by yourselve).
