Excess solar for EV charging - how to automate?

[timselectric]

You put the CTs for the Solarark on the line, you put the CTs for the Vue at the meter.

This is how I have it right now.

But, you are probably allowing export.
This is a zero export situation. So, there wouldn't be any current exporting. For the vue to work with.

 

[Crowz]

My emporia knows when I have excess power and I do not feed to the grid. Its shown as a positive balance.

Basically it shows x amount of power is being used via reading the individual loads and then it looks at how much is coming from the grid. If the loads are greater than the grid used its a positive situation from the solar.

I don't have an ev or their charger so I'm not sure how this would work on that though.

 

[timselectric]

My understanding of how it works. (Which could be way off)
Is that it charges the EV with the excess production.
By monitoring the amount of current coming in versus going out. It doesn't charge when importing. But does charge when it sees exporting.
If the Sol-Ark doesn't allow exporting. The vue wouldn't see any exporting. And therefore never allow charging.
As stated before, I could be way off on how it works.

 

[Crowz]

This is screenshot of right now on my house. If you look at the loads they add up to more than the total usage that is being read off the mains.
The 306 is how many watts that are being provided by solar over the amount being used. When this reaches 100% the solar is running the house. When it goes over 100% Im making more than the total I need aka pure excess. I imagine this would be used in some fashion with the ev charging setup but again I don't have an ev or their charger so I'm not sure.

 

[Hedges]

Can you tell the Vue to maintain, not zero export, rather 100W or 1000W of import?

 

[HarryN]

What kind of hardware interface is required at the Tesla or car charger in order to vary the charge rate?

 

[400bird]

What kind of hardware interface is required at the Tesla or car charger in order to vary the charge rate?

On the OpenEVSE, control is done over wifi and mqtt. Unsure about the Emporia, but wifi for sure.

An EVSE is just a fancy relay that tells the car how much current it can have. So all EVSEs include the hardware needed to communicate available current.

 

[2TrevorJ]

Can you tell the Vue to maintain, not zero export, rather 100W or 1000W of import?

Nope...the excess solar function is just on or off. No config.

 

[Ampster]

What kind of hardware interface is required at the Tesla or car charger in order to vary the charge rate?

The J1772 protocol and interface sends to the onboard charger the current to draw. In the example above, the Emporia EVSE does that based on input from the rest of the Emporia sensors.

 

[Ampster]

Unsure about the Emporia, but wifi for sure.

The Emporia uses a proprietary interface over WIFI,

 

[Hedges]

Nope...the excess solar function is just on or off. No config.

Hardware is easier than software.
Put a bunch of turns of fine wire around the CT. Use step-down transformer and resistor to put current through it.
That will impose an offset of some current reading. Emporia then seeks to zero the CT reading, resulting in actually controlling to some offset current.

 

[ridgebackpilot]

As a new member, I found this thread very useful. My recently-expanded system includes 36 Sun Power rooftop panels, three Tesla Powerwall batteries, and three EVs that need charging. I'm grid tied to my community energy provider via PGE. I've been using a Gen1 Tesla Wall Charger to provide power to the EVs.

Because I can now produce more than 12 kW from my solar array at midday, I'm looking for a way to automate EV charging using surplus solar energy. I've ordered the Emporia Level 2 EVSE to replace my old Tesla Wall Charger. I'm also hoping to use Emporia's Vue Utility Connect to read my Smart Meter via WiFi.

As several here have pointed out, that setup should allow me to charge my EVs using excess solar production automatically, and avoid me having to run out and plug in an EV when the sun comes up and the Powerwalls charge to 100%.

 

[Crowz]

The Emporia uses a proprietary interface over WIFI,

Emporia is definitely proprietary but it can be monitored from home assistant using a plugin that reads from their site.

 

[HarryN]

As a new member, I found this thread very useful. My recently-expanded system includes 36 Sun Power rooftop panels, three Tesla Powerwall batteries, and three EVs that need charging. I'm grid tied to my community energy provider via PGE. I've been using a Gen1 Tesla Wall Charger to provide power to the EVs.

Because I can now produce more than 12 kW from my solar array at midday, I'm looking for a way to automate EV charging using surplus solar energy. I've ordered the Emporia Level 2 EVSE to replace my old Tesla Wall Charger. I'm also hoping to use Emporia's Vue Utility Connect to read my Smart Meter via WiFi.

As several here have pointed out, that setup should allow me to charge my EVs using excess solar production automatically, and avoid me having to run out and plug in an EV when the sun comes up and the Powerwalls charge to 100%.

Maybe you can move some of the panels to generate power at 6 pm to spread out the power generation a bit.

The late afternoon power will have a higher value both financially and better matches the demand curve for most applications.

 

[Ampster]

I've ordered the Emporia Level 2 EVSE to replace my old Tesla Wall Charger. I'm also hoping to use Emporia's Vue Utility Connect to read my Smart Meter via WiFi.

That is a similar setup to mine with the exception of the Vue Utility Connect which I returned when PG&E said they do not connect solar customers to any HAN device. Others have had better luck so do not give up and make a phone call. I kept my Tesla Wall Charger in case I need to charge one of my Tesla's overnight at a faster rate. The Emporia works well charging from excess solar. I use the Emporia Energy Monitor and it calculates excess solar fairly well for my purposes.

 

[Ampster]

Maybe you can move some of the panels to generate power at 6 pm to spread out the power generation a bit.

I don't think there is any benefit to that. His cars presumable can charge at 40 Amps which is 9.6 kW and the solar panels produce 12 kW at mid day. Presumably his peak rate starts at 4PM and he would want any solar after 4PM to go to his loads anyway because at that hour the solar will have tapered off. I don't charge my EVs past 4PM and if I need more by the next day I will start charging again after midnight when the rates are lower.

 

[goldserve]

OpenEVSE along with the WiFi GUI controller in conjunction with MQTT offers a lot of programming. Here is an image with it all working:

 

[cwm9]

Given the setup you have, there's no easy way to do what you want. (You don't feed energy to the grid.)

That's not to say it's impossible, but it's much harder. You need some cooperation from the battery and some hardware hacking.

I'd have to actually see one of the sensors to be sure, but there's a high probability that those sensors are nothing more than loops of wire around a magnetic core, or an extended coil around air, and have no active electronics in them at all.

In which case, a knowledgeable person could easily design a small gadget that could inject an arbitrary signal into one of the ports. You would basically hook up a transformer with an inductance on one coil that matches the inductance of the sensor, and on the other coil you would inject a current with a current amplifier that is equal to the mains voltage times a control variable. If the control variable is positive, the system will interpret that as consuming power, and if the control variable is negative, the system will see that as releasing power, with the absolute value of the control variable telling the system how much power is being moved. Then you need do nothing more than set this control variable according to what is happening to the battery.

That's not too hard: if the battery is fully charged, you trick the system into thinking power is going out to the grid by slowly increasing the "outgoing" power --- but the moment the battery starts to discharge, you decrease the "outgoing" power until the battery starts to charge again (or at least stops discharging), plus a little more. You then wait 30 seconds, monitoring to make sure the battery doesn't start discharging, and then repeat the process of ramping up the current again. It's not a perfect solution, but it will get you close to consuming as much power as possible.

It's the kind of thing a good hardware hacker could slap together in a day if they already had the parts on hand.

 

[SolarRich]

I am doing something similar. We are grid tired but can push power back to the utility. I have a power meter on the power wires coming into the main breaker panel. So I know how much power is going in or out. This power number gets sent every 5 seconds to OpenEVSE charger via a single http command. I wrote the software to do this.
In your case you can't push power to the grid. I would think you would need a power meter on the main power wires and then get data from the inverter. You would have to write your own software. The available power for car charging would be based on no power coming from the grid and PV power number from the inverter. Max out the PV power number w/o pulling grid power. You may need to also use power in/out of the battery.

 

[PaulOr]

What I want is to control the current going to the EV so only the excess solar power is consumed by the car(s) and no grid power is consumed.

Tesla is adding this feature to their ecosystem but we are more DIY here, or at least AIY (Assemble It Yourself).

Not sure whether this is the way you'd want to go, but I've been testing out a beta application (Zerofy) which is attempting to create a solution for exactly this, to automatically charge an EV when there is excess solar. The reason I'm bringing it up is because they recently posted somewhere that they are now integrated with Tesla as well. I haven't personally tested it with a Tesla so I don't know how well it works. But perhaps it could be interesting for you.