Can I charge with excess solar only without draining my Powerwall 3?

[mke]

I'm looking to charge my car from excess solar only. I have battery storage and I do not want the car to be charged from the home battery. I can't figure out a workable way and would like to see if anyone has any recommendations.

I am currently using an Emporia EV Charger.

Setup - please refer to the diagram

• The house has full backup with a Powerwall and the Tesla Backup Switch.
• All loads, including the EV charger, are on the same main panel.
• Powerwall is hooked to the main panel, and it does not distinguish between power from solar (inverter) or power from battery.

Problem

I was informed by Emporia that solar only charging is not possible with the Powerwall. Since the device cannot tell whether power is supplied by solar generation or battery usage, it is unable to determine what is excess solar. While it will not draw on the grid, it will drain the Powerwall. I do not want it to do that.

I took a look at Charge HQ (https://chargehq.net) and am reaching out to understand if this usage can be supported. It will mean getting a different charger as well as paying a monthly subscription if it works. Meanwhile, I wonder if anyone has solved this similar problem.

Thanks in advance for your help!

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[Charge_Rob]

Can the Powerwall be prevented from discharging manually or scheduled during certain times of the day? I'm not familiar with that, but if it could be, would that be a workaround so the Emporia's Excess Solar function would work as expected? I use the Excess Solar feature regularly, but my system doesn't have battery storage.

 

[mke]

Thanks for the response. The Powerwall will try to discharge as soon as it sees a load. There’s no explicit setting to prevent discharging manually. It has a percent of reserve setting, where it usually won’t discharge below depending on whether you want it to save money or maintain backup. However, setting the reserve level too high will also prevent other loads from drawing. It can also cause the Powerwall to draw from grid to charge the battery if it senses it can’t fill the battery before sundown.

Can the Powerwall be prevented from discharging manually or scheduled during certain times of the day? I'm not familiar with that, but if it could be, would that be a workaround so the Emporia's Excess Solar function would work as expected? I use the Excess Solar feature regularly, but my system doesn't have battery storage.

 

[Aubury]

Since you have a Tesla Powerwall, I would consider seeing if you can contact someone there to see if the Tesla Universal Wall Connector can do that. I'm pretty sure it can integrate with the Powerwall and Tesla EVs to charge with excess solar, but it might be able to do it with non-Tesla as well. The universal wall connector has a built-in J1772 adapter so you don't have to worry about plugging in your own adapter every time. It's also pretty affordable as far as connected EVSEs go.

 

[mke]

I’ve tried to look at that as well:

https://www.tesla.com/support/tesla-app/charge-on-solar

It looks to be for a Tesla vehicle only.

Since you have a Tesla Powerwall, I would consider seeing if you can contact someone there to see if the Tesla Universal Wall Connector can do that. I'm pretty sure it can integrate with the Powerwall and Tesla EVs to charge with excess solar, but it might be able to do it with non-Tesla as well. The universal wall connector has a built-in J1772 adapter so you don't have to worry about plugging in your own adapter every time. It's also pretty affordable as far as connected EVSEs go.

 

[Kamuelaflyer]

I set my car to only charge between 1 and 4 pm. By 1 the solar system batteries are fully charged and by 4, there’s still enough sun left to get them to, or near, full. I do live in an extremely mild and sunny climate though.

 

[Aubury]

I’ve tried to look at that as well:

https://www.tesla.com/support/tesla-app/charge-on-solar

It looks to be for a Tesla vehicle only.

Ah that's disappointing. I figured you probably had already looked but wanted to give the suggestion just in case

 

[mke]

Much appreciated! Somehow this is more complicated than I initially thought

Ah that's disappointing. I figured you probably had already looked but wanted to give the suggestion just in case

 

[mke]

I have tried doing something similar. Since I have a small system, and my load during the day can wary, I’ll need to modify the charge rate as well so the car will capture just the right amount. Essentially, it is to take the power from the grey section on the right side of the curve to charge the car.

It needs to be changed continuously though and becomes a job in itself.

All of this is to minimize drawing from grid and minimizing sending power back to grid if my car needs the charge. NEM 3.0 in CA makes power sent to grid more or less worthless during the day.

I set my car to only charge between 1 and 4 pm. By 1 the solar system batteries are fully charged and by 4, there’s still enough sun left to get them to, or near, full. I do live in an extremely mild and sunny climate though.

 

[astrorob]

yeah, i don't think there's a good way to do this. if there is some API for the Emporia charger which allows you to set charge current, and command start and stop charging, you could probably use that in conjunction with the tesla API to hack something together.

there's also a 3rd party iPhone app for the powerwall called "NetZero" (it might exist on android too, not sure.) that has its own automation stuff for the powerwall and i think it can integrate with a couple of EVSEs, but since mine isn't one of them i haven't really looked into it.

my grandfathering onto NEM1 ends in 10 years i think, so between now and then i'll maybe have to get a better EVSE that can be controlled. charge point does have an API but it might only be for commercial customers, not sure.

 

[mke]

Thanks for the suggestion. Based on what you said, it led me to homeassistant (https://www.home-assistant.io/). When that looked like way too much scripting work, I then came across this:

https://evcc.io/en/

which still needs some amount of work, though it seems more about following instructions instead of needing to script.

Unfortunately this works with chargers that support OCPP and my Emporia EVSE is not one of them. Looks like I’ll need to get a Wallbox if I want to give this a try.

Also, quite envious of hearing that you’re on NEM1

yeah, i don't think there's a good way to do this. if there is some API for the Emporia charger which allows you to set charge current, and command start and stop charging, you could probably use that in conjunction with the tesla API to hack something together.

there's also a 3rd party iPhone app for the powerwall called "NetZero" (it might exist on android too, not sure.) that has its own automation stuff for the powerwall and i think it can integrate with a couple of EVSEs, but since mine isn't one of them i haven't really looked into it.

my grandfathering onto NEM1 ends in 10 years i think, so between now and then i'll maybe have to get a better EVSE that can be controlled. charge point does have an API but it might only be for commercial customers, not sure.

 

[astrorob]

Thanks for the suggestion. Based on what you said, it led me to homeassistant (https://www.home-assistant.io/). When that looked like way too much scripting work, I then came across this:

https://evcc.io/en/

which still needs some amount of work, though it seems more about following instructions instead of needing to script.

Unfortunately this works with chargers that support OOCP and my Emporia EVSE is not one of them. Looks like I’ll need to get a Wallbox if I want to give this a try.

Also, quite envious of hearing that you’re on NEM1

interesting, thanks for the pointer to EVCC, i did not know about that. i do have a proxmox server at home so that looks like the right way to go. same problem though, need OOCP. someday.

NEM3 is really bad. do you already have the dynamic pricing that they were talking about? that seems like it will be impossible to know what you are paying for electricity since it changes every hour (i think...) for me the 4-9PM peak pricing is already bad enough. the powerwalls are saving my bacon there but of course they cost $$.

 

[OH2AZ2OH]

Are you using Enphase microinverters? If so, you may (or may not) be able to do what you want using the relatively new Enphase IQ EVSE. I only briefly looked at them as they are definitely on the pricey side.

 

[Mach-Lee]

Can't you just get an Emporia Vue, clip the CT on your grid connection, and set it to do excess solar on an Emporia EVSE when you have positive current flow?

 

[mke]

First picture is the price of electricity from grid, the second picture is the credit of electricity sent to grid. They are both defined in advance but very granular.

NEM3 is really bad. do you already have the dynamic pricing that they were talking about? that seems like it will be impossible to know what you are paying for electricity since it changes every hour (i think...) for me the 4-9PM peak pricing is already bad enough. the powerwalls are saving my bacon there but of course they cost $$.

I'm using the inverter on the Powerwall 3, so the Enphase IQ EVSE won't work for my case.

Are you using Enphase microinverters? If so, you may (or may not) be able to do what you want using the relatively new Enphase IQ EVSE. I only briefly looked at them as they are definitely on the pricey side.

I asked Emporia of this and was told that the device is unable to tell the difference between battery usage and solar generation. As they do not have access to Tesla API, they informed this is not a scenario they would support.

Can't you just get an Emporia Vue, clip the CT on your grid connection, and set it to do excess solar on an Emporia EVSE when you have positive current flow?

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