Charging my EV without draining battery

[dpowell]

Just had the following installed at my house:
(20) REC 410s
Powerwall 3
Tesla backup gateway
Tesla Wall Connector
Not sure if it matters but I'm on SCE NEM 3.0 TOU Prime. I'm trying to figure out how to configure my Tesla Model S and the solar system (guessing it has to be done at the car end) to only charge the car once the Powerwall has finished recharging from it's overnight drain AND charge only using the residual daytime production rather than having it go back to the grid (I'm getting a whopping 2 cents per kWh sell back rate). In other words I want my Tesla to charge without draining the battery or pulling juice from the grid. Is this achievable?

 

[hwy17]

It's technically achievable, but requires some advanced automation between the inverter, powerwall, and charger.

If anyone would have that automation, I expect Tesla would, but it all depends on what's available in the Tesla app. If they don't have that feature yet then it would be quite a custom job to try and program it yourself. I don't know if all that Tesla equipment offers a DIY API or something.

 

[2TrevorJ]

This video was posted yesterday showing Tesla's Solar & EV integration including their excess solar charging functionality.

Should help you out.

Side note...the host makes it sound like excess solar is a unique Tesla feature but to be fair there are a couple other ecosystems out there that can do it. Emporia's Vue monitor and their charger has it...you just have to temporarily disable battery discharge in your inverter's software while using the excess solar function. I use it regularly and it works great.

https://help.emporiaenergy.com/hc/en-us/articles/9227254158103-Excess-Solar-Management

 

[Ampster]

I use the Emporia to do the same with the Emporia EVSE. I have two Teslas and also the Tesla Wall Connector but the integration comes from the Powerwall so I have to use the Emporia to charge from excess solar. The Wall Connector or the Teslas have no way of knowing what my solar production is. That comes from the sensors in the Powerwall Controller.

 

[dpowell]

The video that 2TrevorJ provided a link to appears to be a big part of my solution. However, I can pair my app to the Powerwall but the "Charge on solar" option never appears in my app. The only reason I can think of because I don't yet have PTO from the utility. Could this be the reason?

 

[Ampster]

.....I don't yet have PTO from the utility. Could this be the reason?

I would guess so. Without a PTO your solar is not supposed to be on. I would guess your Powerwall is not turned on either. My PTO was delayed and I turned it on but got no credit for export. That was before I got the Emporia and had to manual adjust the charging rate to optimize the benefit, without incurring charges

 

[time2roll]

I would guess so. Without a PTO your solar is not supposed to be on.

There is also a grid back-up / no export mode that I believe Tesla installers have been setting the new installs to waiting for the utility.

For the OP I recommend reaching out to the installation coordinator.

https://www.tesla.com/support/energy/powerwall/mobile-app/powerwall-modes

 

[Ampster]

That is a good idea so that the Powerwall can be charged as well. Years ago, I heard of delayed PTOs with Powerwalls and the Powerwall lost energy during that waiting period.

 

[OffGridForGood]

I prefer low tech software, and simple agreement:
240-2P relay controls power to the EV charger,
120v control side is powered via a smart plug with my I-phone,
good sunny day, and ESS SOC looking good on Solar Assistant,
switch on the smart plug with my phone.
Hopefully the EV is plugged into the charger.

For my area, every kWh into the car, saves me 51 cents (USD) of 'not-gas' driving, way better than supplying a utility.
The only "Agreement" required is the House Rule: "when you park the EV always plug it into the charger"
Not glam, but works for me.

 

[Ampster]

I prefer low tech software, and simple agreement:
240-2P relay controls power to the EV charger,
120v control side is powered via a smart plug with my I-phone,

My approach is even simpler. I control when and how fast my cars charge from one app on my phone. I then let the Emporia manage the rate after that based on solar production.

 

[pollenface]

If it's a cloudy day, I set the charge rate to 1.5kw, if it's a nice sunny day, I make it 3.4kw

At the end of the day I still need the car to charge enough for the next day even if I'm buying from the grid. We use our EV virtually every day.

 

[Ampster]

At the end of the day I still need the car to charge enough...

Sometimes I have the same challenge. Mine is complicated by high TOU rates from 4-9PM so if I don't get to my target SOC by 4PM, I stop charging until lower rates after midnight.