diy solar

diy solar

Solaredge EVSE with Energy Meter for Charging with excess solar


Solar Enthusiast
May 14, 2020
Las Vegas
I just picked up a full EV (traded in my phev and got a great deal on a Chevy Bolt EUV). I already have a level 2 evse but I've had my eye on the solaredge unit because the data will be in the same mySolaredge app plus it has Charge Via excess solar only options. My PHEV had a max of 4kw I think so when I charge during the day it never had to pull from the grid because my system is 10kw. However my new car can charge MUCH faster at 11kw (9.6kw max on this EVSE).

I like the idea just using from excess solar as this car's battery is much larger so I won't need a full charge daily as I never drive more than 50 miles a day (and that's only 2-3 times a week). However in the manual:

On page 49 it talks about having an energy meter in order to get this to work, which I already have. However I'm unclear how this is to be wired because the energy meter is already setup on the inverter so I have no other connections on the energy meter. Would it be safe to assume the inverter and evse on the same network is enough?
FYI I attempted to connect over wifi and no go. Some other forum posts hint at an ethernet connection, so I may try that. I'm not installing it near the inverter or energy meter so I'd like to avoid running an RS485 connection. I'm run an ethernet cable this week to see will work and will report back in case anyone else in the future finds this thread.
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I cannot help however I am interested in hearing about the eventual success and how it works out for you.
I don't know about the intricacies of your specific solar edge system and how technically inclided you are, but the power regulation can easily be acomplished.

The communication between EV and EVSE in AC charging is through a PWM signal over the Control Pilot signal. The 'charger' (Technically the EV supply, as the carger is inside the car) can report to the car how much power to pull, if any at all. It's well documented and a shame it's not a standard user parameter, as it costs the manufacturer very little to implement - At least in the option of a variable potentiometer or app to set charge rate, for example, if you wanted to charge overnight vs quickly top up for a large trip.

The basic implementation is described here.

You need to have a signal tell you how much excess power your house is actually exporting. This should come from a device installed in your AC supply point - The wires coming from the utility meter.
Once you have that signal available you need to pass it into the EVSE (ideally wirelessly connected if they are not close, but cable options like you describe are common too) that would then command the car charger to a suitable charging rate based on available surplus.

How it works?
The EVSE measures the voltage across the pilot, but the duty cycle can be overrided to command the charge current. It's essentially a current source at 12V, which is pulled down to 6 or 8V by the car with a PWM signal imposed on it that dictates the charge rate.

What they recommend is likelly to be a CAN or RS485 meter. This is not something you can directly interface to a network connection (they just happen to use an ethernet cable, as it's a convenient method to transfer digital data). It would likelly be easier to get another meter if you go that route, rather than messing with the one on the inverter. You then need to connect the meter and the EVSE together using that cable (talk about old fashioned!)

I just posted on another thread of a device I've done which you can use to obtain the instantaneous power in/out of the house, if going the DIY route. You can then send that value over MQTT to another micro, to control the pilot and tell the car how much to pull or to stop if you're drawing too much power. You only need a wifi connection to link them. You can see post #4 here.
The measuring device would likelly be this or preferably (but limited to 16A) this which is a lot easier to work with. They must be based on BK7231 and energy metering IC BL0942 and with the default firmware they don't measure the direction of AC power, so you need to flash my firmware here. You can find instructions on the Elektroda forum under smart home.

Either way - It can be done and you don't need to limit yourself to a particular EVSE, you could try it with your existing one, even modify it accordingly, if you want to limit the charge rate to a static value, so it can be left all day.
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