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Having two OpenEVSEs talk to one another re: chargning current?
Ken Gillett
The easee EVSEs can do this with up to 3 units. They communicate and spread the load so all 3 units can be powered from a single supply.
I'm really hoping this will be incorporated into OpenEVSE.
OpenEVSE Support
This can be done with a little work. OpenEVSE supports "Eco Mode"/current shaper. It grabs its allowed current from a MQTT broker. So what you need is the software to run your desired logic to take the available current and divide it up. A python script or a program like Node-Red would do.
Ken Gillett
Interesting. So best solution is to run my own MQTT broker to run what you suggest and control it all?
I have a server available that could do that. Presumably, any 'script' that can interface with the broker would suffice?
Can you point me at any information to assist with setting this up?
OpenEVSE Support
Here is a basic video on Node Red.
https://www.youtube.com/watch?v=XDrwgMSQrEY
Python with the paho library is not too difficult.
Here are a couple of examples where data is grabbed from solar output then sent to MQTT
https://github.com/OpenEVSE/Solar_MQTT
Revisiting this idea, as I've just set up HomeAssistant with Mosquitto MQTT broker.
I'm still trying to understand MQTT, but from what I've read about publish and subscribe, it seems that there's little handshaking or confirmation of receipt. It also relies on a 3rd node on the network.
Considering the following:
If the ESP32 in the OpenEVSE can even handle the additional task of this.
If the ESP32 can pair with another local ESP32 (In the other OpenEVSE) with an additional interface (Bluetooth) to separate this traffic from the WiFi traffic.
After that, I guess a simple loop running on both OpenEVSEs constantly checking on the partner's status.
IF partner disconnected.
THEN set current limit to 48 amps.
ELSE set current limit to 40 amps.
Keeping in mind that I'm not a software guy, I can't code for crap... I'm better suited with a soldering iron and screwdriver.
Theo Abramovich
Short version: Can I have two 48 amp OpenEVSEs talk to one another such that their total charge current does not go past 80 amps? (IE when one OpenEVSE is idle, the other can use its full capacity, but if both are in use, they're limited to 40 amps each?
Long version:
I'm in the process of installing a (NEMA 3R rated, outdoor) 100 Amp subpanel on the side of my house next to the driveway; my breaker panel is unfortunately on the OTHER side of the house, 60 linear ft away.
I have installed 1-1/4 inch schedule 40 PVC pipe and will be pulling in 2 AWG wire, fed by a 100 Amp breaker in the main panel.
Per US NEC 210.19 and 210.20, the conductors and breaker are supposed to be rated at 125% of the maximum load because charging an EV is a continuous load (Longer than 3 hours.) Therefore, the MOST current I can draw off my 100 Amp breaker and subpanel is 80 Qmps.
The subpanel has two 60 Amp GFCI breakers feeding two separate NEMA 14-60R outlets. (Again, per the above rules, maximum charging current per outlet is 48 amps.)
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