# Possible charge control for charging directly from a solar array



## Tylerkinetics (May 5, 2016)

Does anyone know if Tesla is planning to develop a charge control that will allow your car to directly interface with a solar array? This would eliminate the battery bank and the double inversion that's presently required for off grid home charging.


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## garsh (Apr 4, 2016)

They have nothing planned.

I'm guessing that the use case just isn't that common.


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## mishakim (Sep 13, 2017)

Charging off a Power Wall would be more likely - charge that from solar during the day, charge the car at night, still eliminate the double inversion. And that would fit well with Tesla's integrated vision - Tesla Solar Roof, Tesla Power Wall, Tesla car, all are already controlled from the same app. Plus it would sell more Power Walls, since they're a lot smaller than the car battery pack, so you need several!


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## Tylerkinetics (May 5, 2016)

mishakim said:


> Charging off a Power Wall would be more likely - charge that from solar during the day, charge the car at night, still eliminate the double inversion. And that would fit well with Tesla's integrated vision - Tesla Solar Roof, Tesla Power Wall, Tesla car, all are already controlled from the same app. Plus it would sell more Power Walls, since they're a lot smaller than the car battery pack, so you need several!


 Problem with the power wall seems to be that it is not a 240 V inverter coming out of it, which I guess could be solved with an added transformer.


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## garsh (Apr 4, 2016)

Tylerkinetics said:


> Problem with the power wall seems to be that it is not a 240 V inverter coming out of it, which I guess could be solved with an added transformer.


Ideally, you wouldn't bother converting to AC at all - just pipe the DC directly to the car, like a supercharger.


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## Model34mePlease (Jun 3, 2017)

garsh said:


> Ideally, you wouldn't bother converting to AC at all - just pipe the DC directly to the car, like a supercharger.


Given what Elon is trying to do, I'm surprised that isn't already available.


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## roflwaffle (Sep 25, 2017)

mishakim said:


> Charging off a Power Wall would be more likely - charge that from solar during the day, charge the car at night, still eliminate the double inversion. And that would fit well with Tesla's integrated vision - Tesla Solar Roof, Tesla Power Wall, Tesla car, all are already controlled from the same app. Plus it would sell more Power Walls, since they're a lot smaller than the car battery pack, so you need several!


Ideally, someone would be home enough of the time to charge when the sun is out and minimize the number and use of powerwalls, or any battery pack. An AC inverter is still needed, which is an efficiency hit and another part that will wear out/break, but to me that's a lot less expensive than having a bunch of powerwalls to charge at night, mostly because the cost of energy storage is still high compared to the cost of PV.

Course, I'm assuming a charging powerwall will send any DC power it doesn't need to charge itself up downstream to other DC devices and/or an AC inverter, but I could be wrong about that.


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## Guest (Oct 2, 2017)

I do not know is Tesla planning it or not, but almost all EV's are capable of doing that (charging directly from local source without AC hassle) without any modifications to the vehicle.

Though Powerwall must support that functionality internally (DC-DC charging controller) or externally (DC-plug/terminal with data pins and external charge controller as an optional extra). 
Distance between Powerwall and EV (Tesla, for example) should not be very long. 
Solar power generated in real time will easily travel to the vehicle.
Though PW must also support switchover to grid AC power if software requests to continue (sun down, no storage, SOC below requested).
In case of Tesla, plug will be exactly the same. In case of CCS vehicle, it must be frankenplug (though much lighter and smaller cable).
Maximum expected charge rate can definitely be at least 10kW (5kW from battery, 5kW from grid). 
Theoretically, even 15kW - 5kW from AC grid, 5kW from DC battery itself, 5kW from DC solar - though this bumps up the price of the installation.

I'm not able to estimate payback period (how much that all costs vs how much energy (in terms of money) is saved).
And it only makes sense if solar array is too big for local consumption (excessive storage capability and/or solar production while vehicle home). Due to that, my prediction is that this setup hardly makes sense for average household with an EV.


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## Model34mePlease (Jun 3, 2017)

arnis said:


> I do not know is Tesla planning it or not, but almost all EV's are capable of doing that (charging directly from local source without AC hassle) without any modifications to the vehicle.
> 
> Though Powerwall must support that functionality internally (DC-DC charging controller) or externally (DC-plug/terminal with data pins and external charge controller as an optional extra).
> Distance between Powerwall and EV (Tesla, for example) should not be very long.
> ...


The economic equation here is getting better rapidly as the price of both PV and storage decreases. I think this will be the natural next endpoint and probably fairly soon (at least in many climates).


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## Guest (Oct 2, 2017)

The cheaper solar/storage gets the less reasonable extra complexity is.
Instead of investing 1000$ into extra inverter/control hardware, it's more profitable to install extra 1000$ of solar panels.
Theoretical maximum efficiency gain is less than 10% (as PW is 90% efficient).
If solar panels get even more cheaper, the more power you get. For 1000$ one extra kilowatt could be bought, right now.

If we talk about long term plans (2-3 decades) it's more likely that whole households could switch to DC.
There are very few devices that actually need AC. Most of stuff runs on DC.
If local production (solar) get's widespread (half of households have that) I guess things will start to progress.


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## Wynstonn (Nov 23, 2018)

I have solar to charge my Model 3. I do not have a power wall as a back up when the grid goes down. Is it possible to feed from the Model 3 into an inverter to provide minimal house lighting, etc.?


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## Guest (Dec 10, 2018)

Wynstonn said:


> I have solar to charge my Model 3. I do not have a power wall as a back up when the grid goes down. Is it possible to feed from the Model 3 into an inverter to provide minimal house lighting, etc.?


The only way to get power out of Tesla is to use a cigarette lighter inverter. But it is limited in power.
Slightly more juice can be extracted directly from 12V battery terminals with regular crocodile clips.
High Voltage is not accessible for anything below "professional modification level".


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