Using Cybertruck to top up offgrid solar system instead of a generator

markvan

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I live offgrid with no connection to external electricity provision.
I have a 7 year old 10KW offgrid solar system with 1800ah 2V gel batteries which has perfectly run the whole property but has gotten down to 40% charge after a week of bad weather. I don't have a backup generator, quoted about $10k AUD.
I'm thinking that because the Cybertruck has a power outlet I could use that to recharge my house system after bad weather as there is a supercharger only 30mins away. Is there any misunderstanding I have as to whether this is possible?
Also, I've heard that Powerwall is not available for offgrid, it must be grid connected, Is this actually true?
The time will eventually come to replace the gel batteries and I like the idea of using Powerwalls to power my property and vehicle.





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Ehninger1212

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Correct, power wall is not made to be a dedicated off grid power supply. Just a thought, would you be better off putting that 10k AUD into more solar panels? or storage?

Also, we dont know enough about how much power the CT will be able to supply. So probably not best count on it running the whole home at this point.
 

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Correct, power wall is not made to be a dedicated off grid power supply. Just a thought, would you be better off putting that 10k AUD into more solar panels? or storage?

Also, we dont know enough about how much power the CT will be able to supply. So probably not best count on it running the whole home at this point.
If the CT has VTG, It'll supply up to it's complete battery of power, say 175 Kwh of power.
 

Ehninger1212

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If the CT has VTG, It'll supply up to it's complete battery of power, say 175 Kwh of power.
Right.. if, we simply dont know yet. I sure hope it does.
 

ajdelange

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Power walls definitely can be used in an off grid system (any system in which the utility goes down is an off grid system during that time). There is some trickery required involving the Powerwall synthesizer reference which must be set to a frequency compatible with the inverter (or microinverters) used with the solar panels.

The CT won't have V2G or indeed V2H except in the sense that it has 240 VAC receptacle(s) in the bed. These should be like any other 240 source (adjust for differences between electrical systems in US and Oz e.g. the trucks sold in Oz will have 50 Hz inverters) and as such could presumably be used to top off batteries in a solar system. Theoretically there is no reason why this source could not mimic a backup generator and thus charge Powerwalls too. But two possibilities suggest themselves:
1)Tesla will think this is a great idea and provide special software/firmware in the app, Powerwall and CT to facilitate it
2)Tesla will conclude that this is a bad idea (for whatever reason one of which might be to get you to buy more Powerwalls) and take steps to prevent you from doing this, e.g. declaring that it voids Powerwall and/or CT warranties. I have free supercharging. I doubt that Tesla would like it if I drove into town, picked up a charge, drove home and used that charge to run my house.

My crystal ball is in the shop for its annual polishing so I can't be any more definite. Bottom line is that technically I see no reason that you could not do what you are proposing,
 

delB=0

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I have seen a lot of posts on using the CT for generator backup in an outage, but have gotten confused about exactly how this could be done and I haven't seen any wiring diagrams. Here is an idea, with diagrams (attached pdf file).

To use the 240v CT outlet to power the house when the grid is down, you could use an extension cord to connect the CT 240v outlet to a standard home generator transfer switch via house wiring. The CT would function as the generator. But what if the homeowner accidentally leaves the CT charger plugged in at the same time the CT is powering the house? We have all probably done stupider things than this! You would have a circular situation, with the CT battery powering the house while the house tries to charge the CT battery. Can't be a good thing. So here is an idea to make the system foolproof. The drawings show two cases, both with and without a Powerwall setup.

As shown in the attached file, in an outage the homeowner would first flip a manual transfer switch to disconnect the grid input while connecting the generator input to the house electrical service panel. The transfer switch could be located in the basement. Then flip a rotary switch (could be located in the garage near your EV charger) to disconnect the charger from the house while simultaneously connecting a special 240v outlet on the garage wall to the generator input of the transfer switch. Importantly, only one circuit can be closed at a time, so it is impossible to have both switched circuits active at the same time. Now connect the CT 240v outlet to the 240v outlet on the wall with a purpose-made extension cord. This connects the CT to the generator input of the transfer switch. The CT can now power the house without the house trying to charge the CT at the same time.

The Baomain Rotary Cam Switch SZW26-63/D303.3 is rated at 660V 63A, which should be plenty of capacity for the purpose. It can handle 3 phase wiring (3 poles), but we need only 2 of the 3 available poles for each of the two circuits (house-to-charger and CT-to-house). https://baomain.com/collections/cam-63a

If you have a solar Powerwall, it would continue to function as an isolated system and top off the Powerwall battery while separately the CT powers the house. If you want to run the house on the Powerwall for awhile (if you need to drive the CT somewhere), you would just flip the two switches back to their original positions and disconnect the extension cord between the CT and the special 240v outlet on the garage wall. The Powerwall, if you have one, would power the house while the CT is out.

I hope this is clear enough. It avoids the need for a complicated intelligent controller and it integrates well with a Powerwall system, by keeping it separate. It is just an idea for now. Does anybody see any safety problems or have any alternative ideas?

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Crissa

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Well, you don't power the EVSE circuit. Generally, aux power is delivered to a subset of circuits, not all of them at once.

-Crissa
 

FullyGrounded

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From what I read, you might consider wind generator as backup. You state that bad weather led to poor charge; and as is typical, wind extremes come with bad weather. So, common thought is a low-cost wind back up. Now, it may not provide all you need for backup; but, for what remains at times, maybe the CT would suffice. peace
 
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markvan

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Thanks guys, all helpful answers.
 

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