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Gen3 Home Charging with powerwalls

Hi, apologises if this is not the correct forum for this, but I can't see to find anything specific to home chargers.

I currently have a 9kW array and a Powerwall 2 and I'm now in the market for an EV since the company car is going back and the model Y is at the top of the list.

So my question is regarding the gen3 charger.
With Tesla offering products such as solar panels, powerwall, backup gateway etc, I can't seem to find out if the gen3 charger has any functionality to be able to charge from the powerwall2 if over a certain % or you can set it to charge from the solar generation. Ideally, I'd prefer to only charge the car if I'm exporting back to the grid, with the option to change this and charge from the PW during in typical grey cloud days.

So if this possible at all?
I'm hoping they have this option, or it's being thought about and will be released in future updates, but any info on this would be great.

Thanks.
 

jjrandorin

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The only functionality they have with that is when the system is off grid. There is no tesla provided synchronization to home charging when on grid. When off grid, there is a setting to prevent your tesla from draining the batteries but it does not work when on grid.

People are working on third party stuff but nothing from tesla direct.
 
The only functionality they have with that is when the system is off grid. There is no tesla provided synchronization to home charging when on grid. When off grid, there is a setting to prevent your tesla from draining the batteries but it does not work when on grid.

People are working on third party stuff but nothing from tesla direct.
Can you share some details on the "third party stuff"? I'm also trying to charge my EV only with excess solar.
 

holeydonut

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I was originally just going to say that as long as you charged your EV when the sun were shining, the vast majority of energy going into the EV will be sourced from renewables. So even if it's not 100% the solar coming off of your roof, it's still relatively "clean".

But now I realize just how different California's energy profile is from the National Grid sources in the UK.

Yesterday at noon 67% of the energy was being supplied by Renewables in California. Edit: and as we learned in the NEM 3.0 megathread... the residential solar generation localized at the endpoint homes simply "reduces demand". So total renewables is actually greater as a % of total energy being consumed. But nobody has a measurement/estimate for this. If you live next door to h2ofun and charge on a sunny day, there's like a high chance your charging will be from his solar exports heh.
1651768467729.png



But for National Grid, only 28% was coming from renewables at noon. Edit: Presumably residential rooftop solar is also just a reduction of demand measured by NG. So, overall renewables % is probably a bit higher for total actual demand.
1651768616671.png



I hope Tesla figures out a way to dynamically adjust charging speed to match the solar exports you produce at a given moment.
 
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holeydonut

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There is a thread somewhere here on TMC about people working on doing this. I will have to dig it up when I get some time to try to find it.


Is it this one?

 

jjrandorin

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Is it this one?


Yeah thats it, thanks for providing the link to it here.
 
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Here's a thread from someone using Home Assistant to adjust charging speed:
 

miimura

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There is also a third party system that hooks into the Tesla API on the car side and the inverter on the solar side. I cannot vouch for it, but apparently it does work for people in the US. It is only officially supported in Australia. Zappi is definitely a good choice in the UK.

 
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There is also a third party system that hooks into the Tesla API on the car side and the inverter on the solar side. I cannot vouch for it, but apparently it does work for people in the US. It is only officially supported in Australia. Zappi is definitely a good choice in the UK.


I've been using Charge HQ in the US and love it.
 

jjrandorin

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Oooo ChargeHQ works exactly as nwrey seems to want.

When my Powerwalls filled up, the car started to charge at the exact load necessary to have the total home loads equal the solar production.

So the net grid impact goes to almost zero. The EV + home are soaking all the solar production.

I may have to give it a try.
 
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Oooo ChargeHQ works exactly as nwrey seems to want.

When my Powerwalls filled up, the car started to charge at the exact load necessary to have the total home loads equal the solar production.

So the net grid impact goes to almost zero. The EV + home are soaking all the solar production.
I would be interested to hear how well it works on partly cloudy days when the solar production is rapidly changing minute to minute. Anyone know how often they poll the system and update the charge rate?
 

holeydonut

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I would be interested to hear how well it works on partly cloudy days when the solar production is rapidly changing minute to minute. Anyone know how often they poll the system and update the charge rate?

Yeah, it samples once per minute. So it's not 100% real-time-perfect. But it's pretty close. Here's what it looked like during a partial-cloudy charging. My solar system is a smallish 6.7 kWp AC system that would be generating around 6.5 kW at 1pm local time. But due to clouds, it's a choppy ~3.8 kW. I stacked the 3 screenshots side by side for that one data point. Charge HQ set my car charging to 10A at that minute, so the total home load soak mostly equaled the solar output of ~16A.
1652046581535.png





Here's Charge HQ the next minute; you can see it's telling me the car charging is about to be terminated due to lack of energy from the solar. 6A is the minimum charge rate it would support. Please ignore that my home load shot up to 5.23 kW in this example... folks were doing laundry at the time, which likely further messed with Charge HQ trying to use the EV to soak up solar.
1652046601210.png



Here's the Tesla app tracking my daily grid usage. Right before noon my Powerwalls filled up. Starting there, it tried its best to minimize my grid usage by exporting my solar into the EV. And once the EV was charged to 80% (the limit I set), solar started going to the grid. But since it's not a perfect flatline-zero, that means this software likely won't work if you disconnected yourself from the grid.
1652046675506.png



If I try to charge off grid, I think it's better for me to just set my Powewall max charge (before car charging is enabled) to like 85%... and then let the EV try to charge at 25A so only the combined Tesla ecosystem software is doing the charge balancing. I think ChargeHQ would just mess things up for 100% off grid charging. BTW, I'm set to "cost savings" mode, so when my Powerwalls are charging from solar, my house is taking energy from the Grid. I think if you had "self powered" in mind the only real difference would be your Powerwalls would take longer to charge.



I think the main benefits of Charge HQ are:
1) Reducing your NBCs for any grid export. I'm sure @Redhill_qik and @miimura will correct me, but I think you get hit with a ~$0.02 to $0.06 (off-peak vs peak) per kWh NBC when you export energy under normal NEM. So, you dodge this cost since you pushed to your car instead of to the grid.

2) Being able to tell people you're 99% charging your EV from solar. I've heard the Range Rover / BMW / Audi driving folks near me bringing up how an EV is still charged from dirty energy from the grid, so an EV is just like burning gasoline. But having this software (and enough solar like H2ofun) can make it so you could tell those folks that you are 99% solar powered on your EV charging. I just wish PG&E let me put more goddamn solar panels on my roof to make this a reality.


The main drawback of Charge HQ (aside from the kilometers thing) is:
They don't support the PG&E TOU rates. Their system does not realize that I'm punished by using solar to charge an EV starting at 3pm local time. So for now the software seems good, but I'll turn it off since I don't want to lose 3pm shoulder solar exports.
 
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