Powerwall behaviour during grid outage

[MadScientist]

I'm going to add a second Powerwall 2 to my system in a few weeks’ time and the installer came around to do a preliminary survey. One thing he mentioned, which I regret not quizzing him further about, is that if there was a grid outage and it went into 'island mode' only one of the batteries would be able to act as a backup for the house load.

Is that correct? Doesn’t make much sense to me. Thanks for any feedback.

 

[mongo]

I'm going to add a second Powerwall 2 to my system in a few weeks’ time and the installer came around to do a preliminary survey. One thing he mentioned, which I regret not quizzing him further about, is that if there was a grid outage and it went into 'island mode' only one of the batteries would be able to act as a backup for the house load.

Is that correct? Doesn’t make much sense to me. Thanks for any feedback.

Hard to say, but maybe they meant one battery was "sufficient" to backup the house, power wise.

Or it could be a weird setup due to panel limits where the second battery is on the grid side of the Gateway. This would only make any kind of sense if you have solar and get credit for export.

 

[KennethS]

We had a second Powerwall added to our system several months ago and have no such limitation. Both Powerwalls operate in tandem. I would definitely challenge your installer on that.

 

[Dilly]

I started with one with a gateway 1. When the second with a gateway 2 was added they both run as one but not only that, the 3.6kWh output of the first was increased to 5 and the second set at 5, giving 10kWh peak output. Gateway 1 was removed.

it makes no sense at all that only one will “island”. I would certainly establish the facts.

 

[MadScientist]

Thanks for the replies. I certainly need to seek clarification on this.

 

[Andywil]

Thanks for the replies. I certainly need to seek clarification on this.

I think you need to find another installer as this one obviously doesn't know what he is talking about.

 

[phil4]

I've got 2, and they both work together normally and in backup mode.

Perhaps he's confusing it with 3 phase setups, where as I understand it, during backup mode only one of the phases is powered, so if you've a battery on each only one is going to be doing anything.

I'm surprised though that someone who should be a Tesla trained and approved installers doesn't appear to know what they're doing, so you might want to try someone else.

 

[MadScientist]

Just had a word with the installer. He was confusing with a 3 phase set up and admitted his mistake. It was actually one of their surveyors who came around and not the actual guy who will be doing the installation.

 

[Js1977]

Just had a word with the installer. He was confusing with a 3 phase set up and admitted his mistake. It was actually one of their surveyors who came around and not the actual guy who will be doing the installation.

I gather you are waiting for it to be VAT free?.... Can I ask what the quote was? Im also also thinking on having another one put in

 

[mongo]

Perhaps he's confusing it with 3 phase setups, where as I understand it, during backup mode only one of the phases is powered, so if you've a battery on each only one is going to be doing anything.

I think you can have multiple individual phases backed up (at least one Powerwall per phase), but you can't run 3 phase devices (the PW operate independently).

 

[MadScientist]

I gather you are waiting for it to be VAT free?.... Can I ask what the quote was? Im also also thinking on having another one put in

£6417

 

[Js1977]

£6417

Thanks for that!

 

[phil4]

I think you can have multiple individual phases backed up (at least one Powerwall per phase), but you can't run 3 phase devices (the PW operate independently).

I'm not for one second saying you're wrong, I just recalled some oddity about 3 phase setups, and seems it was a good guess

 

[mongo]

I'm not for one second saying you're wrong, I just recalled some oddity about 3 phase setups, and seems it was a good guess

Yeah, it's a thing in a different country and I could be off also.

 

[WannabeOwner]

Like others, I have two powerwalls and in a power cut they both discharge until both are empty.

 

[ACarneiro]

I think you can have multiple individual phases backed up (at least one Powerwall per phase), but you can't run 3 phase devices (the PW operate independently).

That is not my understanding.
What I think happens is that only one of the phases is backed up during an outage therefore you can’t run three-phase devices and they recommend putting critical loads on the backed-up phase.

The Powerwall 3 phase setup is not really very good at the moment. I’m hoping this will improve and only then will I consider installing the system at our place in Portugal.

 

[mongo]

What I think happens is that only one of the phases is backed up during an outage therefore you can’t run three-phase devices and they recommend putting critical loads on the backed-up phase.

If you can backup one phase, you can duplicate that setup to backup a second phase. However, you can't synchronize 3 sets to run three phase loads.

 

[ACarneiro]

Well, still seems like a bit of an oversight on what is now a fairly mature energy product.
I am hoping "proper" three-phase support will be considered once Tesla start selling Powerwall in more European countries (where Three-Phase supplies are far more common)

 

[mongo]

Well, still seems like a bit of an oversight on what is now a fairly mature energy product.
I am hoping "proper" three-phase support will be considered once Tesla start selling Powerwall in more European countries (where Three-Phase supplies are far more common)

Proper behavior requires a true three phase unit. With the Powerwall 3, they might be able to do that as those are theoretically linkable. Basically you need all three inverters hanging off the same bank of batteries. Otherwise you can only support three phase until the highest draw single phase unit is drained.

 

[ACarneiro]

Proper behavior requires a true three phase unit. With the Powerwall 3, they might be able to do that as those are theoretically linkable. Basically you need all three inverters hanging off the same bank of batteries. Otherwise you can only support three phase until the highest draw single phase unit is drained.

Yes, that's a good point. I'd forgotten each PW have their own inverter so you can't "share" the total capacity over the three phases...
Thank you