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Planning for a grid outage with PW2?

Vostok

Active Member
Jul 1, 2017
1,677
1,789
Sydney
I’ve been advised that there will be a scheduled grid outage for up to 8 hours (during the day) in my area and so I want to have my PW2 fully charged before it starts. The forecast in Sydney is pretty ordinary this week so I can’t rely on it being sunny to power my house.

So what’s the best way to prep for this? One option is to use TBC mode to ensure the battery is charged to 100% from the grid before the peak period starts (2pm) on the day prior to the outage, then switch the Powerwall off using the little switch on the side to preserve the power, then turn it back on again in the morning before the outage starts. But is that what the little switch does?

Another option is to use TBC mode to get the battery charged to 100% by 2pm the previous day, then set the “reserve for power outages” level in the App to 100% so that I’ll be on grid power until the grid outage and then the PW will take over automatically.

Thoughts?
 

paulp

Active Member
Jul 23, 2015
3,082
1,515
Adelaide, Australia
I’ve been advised that there will be a scheduled grid outage for up to 8 hours (during the day) in my area and so I want to have my PW2 fully charged before it starts. The forecast in Sydney is pretty ordinary this week so I can’t rely on it being sunny to power my house.

So what’s the best way to prep for this? One option is to use TBC mode to ensure the battery is charged to 100% from the grid before the peak period starts (2pm) on the day prior to the outage, then switch the Powerwall off using the little switch on the side to preserve the power, then turn it back on again in the morning before the outage starts. But is that what the little switch does?

Another option is to use TBC mode to get the battery charged to 100% by 2pm the previous day, then set the “reserve for power outages” level in the App to 100% so that I’ll be on grid power until the grid outage and then the PW will take over automatically.

Thoughts?
Its as amphead has described. You can also test it by turning off your power once at 100%.
note if you have 3 phase only 1 phase is backed up. If you are single phase your max draw will be 5kw. Not sure what happens if you exceed that.
 

Vostok

Active Member
Jul 1, 2017
1,677
1,789
Sydney
note if you have 3 phase only 1 phase is backed up.
I have 3 phase. I know which circuits and lights are connected to which phase, but unfortunately one of the rooms I want powered is on a different phase, so I will run an extension lead to it prior. One day I will get a sparky to swap around some of the circuits to different phases to optimise the backup.
 

atj777

Member
Feb 25, 2020
210
67
Australia
I don't understand why you wouldn't charge to 100% the night before when power is cheaper.

It takes around 4 hours to fully charge a PW2 (around 24% per hour). Just set up TBC before you go to bed the night before. The PW2 will be at 100% at the end of any off-peak period you set, as long as you set a long enough period. You could set off-peak to be from the start of your cheapest power through to the time you expect the power to go out. Note that it seems to pace itself with charging to get to 100% right near the end of the off-peak period (although not always and I can't work what the variable is).

Note that it is best to make any changes with TBC as late in the day as you can. I have found that making even minor changes in the middle of the day make it do really weird things for a short period (like sending power to the grid) so any changes I make I do after 10pm when I'm on shoulder rates.
 

Vostok

Active Member
Jul 1, 2017
1,677
1,789
Sydney
I don't understand why you wouldn't charge to 100% the night before when power is cheaper.

It takes around 4 hours to fully charge a PW2 (around 24% per hour). Just set up TBC before you go to bed the night before. The PW2 will be at 100% at the end of any off-peak period you set, as long as you set a long enough period. You could set off-peak to be from the start of your cheapest power through to the time you expect the power to go out. Note that it seems to pace itself with charging to get to 100% right near the end of the off-peak period (although not always and I can't work what the variable is).

Note that it is best to make any changes with TBC as late in the day as you can. I have found that making even minor changes in the middle of the day make it do really weird things for a short period (like sending power to the grid) so any changes I make I do after 10pm when I'm on shoulder rates.
I set it to TBC yesterday. It is very wet and dark in Sydney today and it’s trying to charge to 100% right now, before 2pm, but it’s clear it won’t make it, currently at 50%. TBC has screwed up big time. So I might need to mess with the “Price Schedule” tonight, after peak period is over, to force it to charge to 100% overnight.
 

atj777

Member
Feb 25, 2020
210
67
Australia
I set it to TBC yesterday. It is very wet and dark in Sydney today and it’s trying to charge to 100% right now, before 2pm, but it’s clear it won’t make it, currently at 50%. TBC has screwed up big time. So I might need to mess with the “Price Schedule” tonight, after peak period is over, to force it to charge to 100% overnight.
What did you set your Price Schedule to?

It will only charge the battery during Off-peak and it should take no more than 4 hours to go from 5% to 100%.

All through Winter (until a couple of weeks ago) I had mine set to Off-Peak for 00:00-04:00 and Peak from 07:00-00:00. It would be at 100% at 4am. Between 4am and 7am the house would be powered partly by the Powerwall and partly by the grid. I have no idea how it decides. By 7am I could have anywhere between 75% and 95% and from then it would only power the house from the Powerwall (unless the Powerwall dropped to the reserve of 5%).

As it has warmed up and there's been more sunlight, I have increased the Peak period and reduced the Off-peak period and it has always done what I expected it to do. On Sunday morning I had Peak 00:30-00:00 and No Off-Peak. For some reason it still charged the battery a tad (but only 0.4kWh).
 

Vostok

Active Member
Jul 1, 2017
1,677
1,789
Sydney
What did you set your Price Schedule to?

It will only charge the battery during Off-peak and it should take no more than 4 hours to go from 5% to 100%.
I set my price schedule to the actual tariff, i.e peak from 2pm to 8pm and off-peak from 10pm to 7am.

In my experience, TBC only charges the battery from the grid at shoulder rates to ensure the battery is 100% before peak starts at 2pm. It doesn’t charge at off-peak rates before shoulder starts at 7am.

The battery stopped charging at 2pm with charge level on 57% or something. I then set “reserve for power outages” to 100%. An hour later TBC decided to fully charge the battery at peak rates instead of waiting for offpeak! I shoulda waited before setting to 100% 🤔

TBC sucks and does really weird, unpredictable things. But, at least I have a full battery now for when the grid goes off.
 

atj777

Member
Feb 25, 2020
210
67
Australia
In my experience, TBC only charges the battery from the grid at shoulder rates to ensure the battery is 100% before peak starts at 2pm. It doesn’t charge at off-peak rates before shoulder starts at 7am.
Not my experience at all.

Here's mine from this morning. Battery only charged during the Off-peak and then was discharging during shoulder and Peak (but not immediately). Powerwall was at 100% at 3:55am and stayed at 100% until 5:38am. It then dropped to 86% by the start of Peak.

IMG_8294.jpg


I wonder if it is because I have 3 PW2 and the system "knows" I can get through the peak period.
 
Last edited:

Vostok

Active Member
Jul 1, 2017
1,677
1,789
Sydney
Battery only charged during the Off-peak and then was discharging during shoulder and Peak (but not immediately). Powerwall was at 100% at 3:55am and stayed at 100% until 5:38am. It then dropped to 86% by the start of Peak.
I suspect the behaviour you are seeing is because you have no shoulder period in your schedule between peak and off-peak at midnight. You’ve set your schedule so that offpeak starts the instant peak ends.

I have “shoulder” periods defined either side of peak, that’s the only difference I can see. But that seems to make TBC operate differently.
 

atj777

Member
Feb 25, 2020
210
67
Australia
I suspect the behaviour you are seeing is because you have no shoulder period in your schedule between peak and off-peak at midnight. You’ve set your schedule so that offpeak starts the instant peak ends.

I initially had a shoulder from 10pm to midnight and if I remember correctly, it behaved exactly as the Shoulder between Off-peak and Peak did (see below). i.e. I would get some household usage from grid and some from battery. The battery only ever charged in the Off-peak period.

I removed it because it wasn't needed at all. If there was enough left in the battery to get to midnight I saved money. If I hit the Reserve before midnight it would take power from the grid anyway.

This is the way mine works (and how I would expect it to work). I don't understand why yours doesn't and I don't see how the extra shoulder period would make a difference (and didn't seem to for me).

Off-peak: Battery charges from grid until 100%. House is powered fully from grid.
Shoulder: Battery does not charge and house is powered partially from battery and partially from grid
Peak: House powered totally from battery (and solar if available). Battery charges from excess solar.
 

Vostok

Active Member
Jul 1, 2017
1,677
1,789
Sydney
So how did the the grid outage and PW go?
Would you believe that there was no outage - the section of street they were working on and for which they turned the power off didn’t impact our house.

Surely they would have known which bits of their network would be affected 🤬 If they letterboxed additional houses “just to be safe” that‘s ridiculous.

I’ll still get a sparky in to swap some of the phases around. It’s an elaborate process to run extension leads to my study, our instant hot water system, and our NBN modem on Phase B sockets from the nearest socket running on Phase A, which is backed up by PW2.

Our hard wired smoke detectors use one of the two power circuits on Phase A which is a complete waste - they have their own individual battery backup in the event of a grid outage! That should be switched to Phase B and the more important of the two Phase B circuits put on Phase A. There’s nothing critical on Phase C.
 

paulp

Active Member
Jul 23, 2015
3,082
1,515
Adelaide, Australia
Would you believe that there was no outage - the section of street they were working on and for which they turned the power off didn’t impact our house.

Surely they would have known which bits of their network would be affected 🤬 If they letterboxed additional houses “just to be safe” that‘s ridiculous.

I’ll still get a sparky in to swap some of the phases around. It’s an elaborate process to run extension leads to my study, our instant hot water system, and our NBN modem on Phase B sockets from the nearest socket running on Phase A, which is backed up by PW2.

Our hard wired smoke detectors use one of the two power circuits on Phase A which is a complete waste - they have their own individual battery backup in the event of a grid outage! That should be switched to Phase B and the more important of the two Phase B circuits put on Phase A. There’s nothing critical on Phase C.
Your smoke detectors use bugger all power. Chuck an amp meter over the cable and you’ll be able to quickly work out how many decades it would take to recoup the cost of a wiring change off your backup circuit.
if however your smokies are connected to your security system that has electric door strikes….well that uses a lot of power but equally its the sort of thing you do want on backup.
 

Vostok

Active Member
Jul 1, 2017
1,677
1,789
Sydney
Your smoke detectors use bugger all power. Chuck an amp meter over the cable and you’ll be able to quickly work out how many decades it would take to recoup the cost of a wiring change off your backup circuit.
Yes I know smoke detectors use almost no power. That‘s not relevant to why I want them moved. I have 6 power circuits - 1 & 2 are on Phase A, 3 & 4 are on Phase B and 5 & 6 are on Phase C. Smoke detectors are on circuit 2.

I want PW2 to back up circuits 1 & 3, as those two circuits run the bits of the house I most want to keep running if the grid goes out. The only way to do that is put circuit 3 on Phase A instead of B. The simplest way to do that is swap circuits 2 & 3 in the sub-board.

Seems possible the smoke detectors are on the lighting circuit, which you probably do want backed up for obvious reasons.
They aren’t. I also have 6 lighting circuits which are paired up identically as the power circuits are - 1 & 2 are on Phase A, 3 & 4 are on Phase B and 5 & 6 are on Phase C. I also want two of the lighting circuits swapped so that the two lighting circuits I most want powered in a grid outage are backed up too.
 

cafz

Member
Jul 17, 2020
522
495
Australia
6 lighting circuits! That must have been built for a bunch of those high power halogen downlights that used to be popular... or a hydroponic enthusiast.
 

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