How to dynamically simulate an EV plug disconnection in order to automate charging power setup

Question

I bought a well-made Chinese charger for our Zoe ZE50 R110 electric vehicle.

It can be set to various charging levels (8,10,12,16A at 220V), but as a safety (I guess), the procedure requires me to disconnect the cable from the car before I can change the charging level.

Here is the interesting part : since I live offgrid, I wish I could change the charging level automatically with a microcontroller according to actual solar panel production (or production leftover).

The deal is to simulate disconnection of the EV plug.

I am not sure what kind of relay would be OK. I feel like electromechanical relays are safer and lower cost.

I also though about

1. disconnecting the charger first on the mains side with a regular AC power relay
2. so I can safely simulate disconnection on the EV plug with an almost usual power relay (the cable is no more energized)
3. I now reconnect the mains (upstream), no charge so low power
4. Now I can set the charging level (hacked charger or with a servo motor pushing on the buttons)
5. Eventually I "reconnect" on the vehicle side

However, (5) might still be hazardous ...I fear high power transients could quickly ruin the relay or even put my offgrid home on fire (*).

I understand additional electronics might be needed, or some "partial relay" as shown in some schematics. But I find it difficult to get proper educated info, as it gets drowned in usual charging procedures and numbers.

NB: (*) sure, there are also regulations, but my question here is only technical

Update: also discovered What does an EV "wall socket charging cable" do? which provides lots of info, but which looks like overkill in my use case.

Answer 1

UPDATE: Your requirement is already solved by the Wallbox Pulsar Plus or Myenergi Zappi, both of which can put CT clamp meters on your service wires and redirect solar surplus to the car, dynamically on the fly. They're made for this.

I bought a well-made Chinese charger for our Zoe ZE50 R110 electric vehicle.

STOP. You need to watch the first 16 minutes of this video. It says it doesn't apply to Euro Type 2 connectors but actually, the protocols we care about are exactly the same. So watch it. Really.

It does a sufficiently thorough job of describing how the tech you're hacking actually works.

You need to be up to speed to continue this conversation.

Here is the interesting part : since I live offgrid, I wish I could change the charging level automatically with a microcontroller according to actual solar panel production (or production leftover).

Well, that's all just manipulating the square wave on the CP pin. That can happen on the fly (watch it here at 29:29), and that ability is for energy management:

• Power Sharing a single power provision rate increases/decreases as EVs plug in or finish
• Service overload prevention, like the way the Zappi puts a CT on your service wire
• Load shed under control of power company
• Having the EV draw only surplus power from solar or other home generation etc. Kind like what you're trying to do.

I'll grant you there isn't much consumer-ready product in the last category, but all the underlying technology is in-place and ready to rock. The hard parts are done.

The deal is to simulate disconnection of the EV plug.

Now you know! Interrupt the PP pin, and the EV will think you have pushed the button on the Type 1/2 connector, and it will voluntarily stop drawing current to avoid a big arc. That was easy.

Or interrupt the CP pin which will both make the EV stop charging and also make the EVSE think you unplugged. (the EVSE doesn't necessarily see the PP pin; it doesn't really need it).

It can be set to various charging levels (8,10,12,16A at 220V), but as a safety (I guess), the procedure requires me to disconnect the cable from the car before I can change the charging level.

What a dumb design, changing charge rate on the fly is part of the spec. Is it making you do this through some sort of cheesy UX? I would send it back and look for a different unit better suited to hacking. Though I would barely call it hacking when you are using EVEMS kit for the purpose to which it is designed.

Or you could jump in front of the Chinese unit and generate your own square wave out the CP line. Or simply clip theirs off so it is shorter duty cycle than it's trying to output.

That would let you continue to use the Chinese EVSE's first-rate ground-fault protection LOL, and the big "clack" contactor contained therein, by manipulating the CP line back to it. Then you control the CP line to the car and relay the EV's request for charge (i.e. its changes in resistance/voltage on the CP line).

Or you know, they have an Open EVSE project where you can literally build the EVSE from scratch your way.

Answer 2

For the relay on the DC side, as long as you take one rated for the current and voltage (with enough margin for both) your should be fine (nb : make sure it is a DC rating, cutting high DC current is more difficult than cutting AC).

Or if you a worried about cutting DC, but you are fine cutting the AC side, then you can replace step 5 by :

5. disconnect (again) the mains

6. reconnect the DC side (no current flowing)

7. re-connect the AC side

It would help if you specified the characteristics of the EV side (what voltage and what current). But there exist relays that can carry HUGE currents. For example : it is likely hugely overkill (1000V 1000A DC), but just to show you that you can find relays suitable for electric cars.