Discussion: Powerwall 3 [Speculation / Discussion etc]

[apacheguy]

That isn't how it works. From the looks of it the PW3 is not designed to be able to integrate with an external solar system. You could probably install a PW3, but it would act like a standalone PW with no knowledge of solar. (So, no charging from solar when the grid was down, no solar self-consumption support, etc.)

Not to mention that Tesla doesn't sell Powerwalls as just parts, nor do they support, allow?, self-installation.

If you want to integrate with external solar you need to go with a Powerwall 2 system.

PW2 is a deal breaker for me. I mean if PW2 is the only option I will look elsewhere for my battery storage needs.

What is the technical explanation for PW3 not integrating with an existing solar system if it replaces the inverter? Setting aside positive grounded panels.

 

[miimura]

PW2 is a deal breaker for me. I mean if PW2 is the only option I will look elsewhere for my battery storage needs.

What is the technical explanation for PW3 not integrating with an existing solar system if it replaces the inverter? Setting aside positive grounded panels.

My understanding is that the PW3 integrates a solar charge controller that charges the battery directly from the DC solar panels. In order to integrate with existing solar, they have to replicate the same CT measurement system and AC couple the PW inverter to the existing solar inverter just like the PW2 system does. The way I see it, the PW3 is really a replacement for the Powerwall+ that had a string inverter stacked above a PW2 and shared the breaker and embedded computer. A PW+ and the Backup Switch that goes behind the meter could be a complete system without a Gateway. Surely, the PW3 is the same in that regard.

I really don't understand your dislike for the PW2 system if you have existing solar. Do you care to explain your rationale?

 

[Vines]

PW2 is a deal breaker for me. I mean if PW2 is the only option I will look elsewhere for my battery storage needs.

What is the technical explanation for PW3 not integrating with an existing solar system if it replaces the inverter? Setting aside positive grounded panels.

Why is PW2 a deal breaker for you?

As stated above there are choices they made in the PW3 product design that aren't compatible with 3rd party solar. Honestly, it can be a pain for installers to have a mix and match of tons of different inverter suppliers so I can see why Tesla made this choice. AC coupling with frequency shift control isn't super elegant with the PV inverters potentially having a totally different idea in their (older) firmware. It's pretty ok with more modern firmware, but still subject to conversion losses and isn't really helping any other way, except compatibility.

I know some companies (including the one I work for) will not install batteries with solar they didn't install, so I think the industry is moving in the direction of holistic backup systems.

It can be a difficult transition with existing solar customers because some of the most ardent solar supporters also paid a lot more than today's prices for their system 10 years ago and want to capture the rest of that value.

 

[MP3Mike]

What is the technical explanation for PW3 not integrating with an existing solar system if it replaces the inverter? Setting aside positive grounded panels.

Are you thinking that you would get a PW3, and remove your existing inverter and use the PW3 for that instead? I suppose that is possible, depending on what you have now, but it is possible that you would have to rewire your solar panels. (If it is SolarEdge you have to remove their power optimizer and install the Tesla rapid shutdown devices.)

But most companies won't touch, or make changes to, an existing system.

 

[Vines]

Are you thinking that you would get a PW3, and remove your existing inverter and use the PW3 for that instead? I suppose that is possible, depending on what you have now, but it is possible that you would have to rewire your solar panels. (If it is SolarEdge you have to remove their power optimizer and install the Tesla rapid shutdown devices.)

But most companies won't touch, or make changes to, an existing system.

I missed the specifics of wiring up existing panels to the new inverter in my reply above, and I could see this working technically. Wire up the existing modules to a new inverter inside the PW3.

However if the UL 3741 listing for hazard control isn't satisfied, then you would need one MCI per panel, or perhaps for each 2 panels, to satisfy the code requirement for module level rapid shutdown.

 

[h2ofun]

PW2 is a deal breaker for me. I mean if PW2 is the only option I will look elsewhere for my battery storage needs.

What is the technical explanation for PW3 not integrating with an existing solar system if it replaces the inverter? Setting aside positive grounded panels.

Why? I have 7 PW 2's, work great

 

[jjrandorin]

I missed the specifics of wiring up existing panels to the new inverter in my reply above, and I could see this working technically. Wire up the existing modules to a new inverter inside the PW3.

However if the UL 3741 listing for hazard control isn't satisfied, then you would need one MCI per panel, or perhaps for each 2 panels, to satisfy the code requirement for module level rapid shutdown.

Perhaps I am reading this wrong / on getting the wrong insinuations, but I have the impression that Apacheguy would be doing any of this work themselves, and sees code as more guidelines, if even that.

Where I work, one of my co workers (who is an extremely handy person) sees permits as more "the man" so to speak, and is not a huge believer in pulling permits for work he is able to do himself (and as I said he is very, very handy). This feels to me like the same stance as that.

 

[andy92782]

Installation update: After about a week of no activity, Tesla returned to our home to finish the job. The system is now up and running, although not yet feeding back into the grid pending final approval from SCE. The good news is we passed inspection with the city, and even better, the city inspector agreed to let us ground the system at a garden hose pipe just a few feet away rather than continue to rely on the ugly conduit run all the way to the front of the house. Tesla said they'd do this for us but I think we'll need to continue bothering them until it gets done.

 

[apacheguy]

I missed the specifics of wiring up existing panels to the new inverter in my reply above, and I could see this working technically. Wire up the existing modules to a new inverter inside the PW3.

However if the UL 3741 listing for hazard control isn't satisfied, then you would need one MCI per panel, or perhaps for each 2 panels, to satisfy the code requirement for module level rapid shutdown.

Is UL 3741 applicable to solar installations that are 15+ years old? My system doesn’t have rapid shutdown now and it is still approved to operate. If I need to replace my solar inverter, I can’t see how they can require me to comply with new code unless there is a retrofit requirement.

Why? I have 7 PW 2's, work great

The biggest reason is that I can’t fit a PW2 on the side of my house. However, if I can replace my solar inverter a PW3 would fit perfectly in its place.

 

[Vines]

Is UL 3741 applicable to solar installations that are 15+ years old? My system doesn’t have rapid shutdown now and it is still approved to operate. If I need to replace my solar inverter, I can’t see how they can require me to comply with new code unless there is a retrofit requirement.

The biggest reason is that I can’t fit a PW2 on the side of my house. However, if I can replace my solar inverter a PW3 would fit perfectly in its place.

If you want to use a new inverter technology (as opposed to a like for like replacement when an old inverter fails) I would say that you need to follow the new rapid shutdown codes. I am not your AHJ so they are the final arbiter. UL 3741 is an optional way to achieve hazard control with MCI every few modules to create portions of the string no more than 165V. Otherwise you have to have blocks of no more than 80V and that's is typically one or maybe two modules.

The Tesla inverter I think is limited to 5x MCI per string so if you had to do one per panel, your strings could be pretty short. However, the PW3 does have a good number of MPPT so maybe that's not a deal breaker just a bit of rewiring on the roof.

 

[apacheguy]

There is no way I can replace my inverter with a “like for like” if it were to fail. They stopped manufacturing it over 10 years ago. It seems pretty crazy to force solar system owners to completely rewire their system just because they put in a new inverter. I have 20 panels on one string so having to install MCIs and new string would be a nightmare.

 

[Pearl1!]

That would be pretty shady if Tesla installed equipment that didn't match the permitted plans, no?

Happened to me. Not all that uncommon. They’ll update the permitted plans the day they show up.

 

[wwhitney]

UL 3741 is an optional way to achieve hazard control with MCI every few modules to create portions of the string no more than 165V. Otherwise you have to have blocks of no more than 80V and that's is typically one or maybe two modules.

Just a slight expansion on the above: I infer from your comment that Tesla has come up with a UL 3741 solution that is based on MCIs that limit substring voltage to 165V.


But UL 3741 is much broader than that, it's a way to do a hazard analysis on the entire PV system, and there are many avenues for compliance with it as an alternative to the more prescriptive rapid shutdown options in NEC 690.12(B)(2). For example, I understand there are several PV racking manufacturers who have a system where if you use all their racking and installation details, you can install DC strings without any MCIs or other special measures (up to some DC voltage limit, presumably, but a limit that is plausible for the string voltage).

Cheers, Wayne

 

[Vines]

Just a slight expansion on the above: I infer from your comment that Tesla has come up with a UL 3741 solution that is based on MCIs that limit substring voltage to 165V.


But UL 3741 is much broader than that, it's a way to do a hazard analysis on the entire PV system, and there are many avenues for compliance with it as an alternative to the more prescriptive rapid shutdown options in NEC 690.12(B)(2). For example, I understand there are several PV racking manufacturers who have a system where if you use all their racking and installation details, you can install DC strings without any MCIs or other special measures (up to some DC voltage limit, presumably, but a limit that is plausible for the string voltage).

Cheers, Wayne

Agreed, in the commercial space we can install pretty large arrays at up to 1000VDC without any MCI at all when using particular combinations of modules, inverters and mounting systems.

You are totally right that the roof mount product is more limited, and still requires some MCI to be installed, just fewer of them than other systems which require Tigo TS-4, optimizers or mircroinverters per each module.

 

[Vines]

Agreed, in the commercial space we can install pretty large arrays at up to 1000VDC without any MCI at all when using particular combinations of modules, inverters and mounting systems.

You are totally right that the roof mount product is more limited, and still requires some MCI to be installed, just fewer of them than other systems which require Tigo TS-4, optimizers or mircroinverters per each module.

If anyone knows of other residential systems with UL 3741 for pitched roofs, I would like to hear about those.

 

[CrazyRabbit]

If I was tesla I would not want to produce pw2 for the next ten years to cover warranty claims and pw3. I see no reason why pw3 would not be capatible with pw2.

 

[RKCRLR]

If I was tesla I would not want to produce pw2 for the next ten years to cover warranty claims and pw3. I see no reason why pw3 would not be capatible with pw2.

I think there are always going to be situations where a more "generic" battery is necessary. There will likely be a successor to the Powerwall 2 that will remain compatible with Powerwall 2's.

 

[Jeremy3292]

Some of the things noted in this article below haven't been reported in this thread yet I don't think:

Tesla heralds ease of installation, manufacturing assembly as Powerwall 3 shines at RE+

Crowds have flocked to the Tesla booth at RE+, as the American battery and EV maker displayed its new hybrid battery, the Powerwall 3. The battery, which the company is guiding will be available in “summer 2024,” features an integrated inverter and should deliver lower cost energy storage to...

pv-magazine-usa.com

 

[Anubis]

Some of the things noted in this article below haven't been reported in this thread yet I don't think:

Tesla heralds ease of installation, manufacturing assembly as Powerwall 3 shines at RE+

Crowds have flocked to the Tesla booth at RE+, as the American battery and EV maker displayed its new hybrid battery, the Powerwall 3. The battery, which the company is guiding will be available in “summer 2024,” features an integrated inverter and should deliver lower cost energy storage to...

pv-magazine-usa.com

"For large homes that would like backup power capability for longer periods, Tesla staff say that a Powerwall 3 without an integrated inverter will be offered that can be “daisy-chained” to the hybrid battery unit."

Does this suggest the PW3 without inverter could used for those with existing solar instead of a PW2?

 

[MP3Mike]

Does this suggest the PW3 without inverter could used for those with existing solar instead of a PW2?

It's possible but I doubt it. It probably requires a master PW3.