How to manage PW when grid is out and solar power generation is intermittent

[WABarb]

Hi,
Sorry for what may be a simple question. What is the best way to manage PW when the grid is out. Specifically when to shut down PW to preserve enough power to start up inverters.

I have 3 PW 2s and we had worse case scenario a couple weeks ago and PWs were completely drained and grid was off. Solar could not generate power till grid came on.

Background:
Snow storm shut grid down in morning. I didn't have storm tracker on the night before (hard lesson learned) and the PW were at 20% when grid went off. There was no solar being generated because of snow storm and PW ran down to 0. Eventually The sun came out and panels were cleared but the PWs did not charge until grid was restored days later and inverters could come on.

If I understand other posts, my problem was because there was not enough power remaining in the PWs alone to get inverters started. I did try manually switch the PWs on and off... but that was done too late.

The situation:
-grid is off
-PWs are getting depleted (assume the draw is being managed)
-solar can not generate power to charge PWs (night time, cloudy weather or snow cover)

Question:
Is there a setting that would automatically shut down PWs to preserve enough power to later start up solar inverters. Or is this a manual step.
I know this means being without power for a short time - but this is just until solar can charge PW again. If this is manual, at what % Power should I do that. If there is a hidden reserve % - it's not enough to start my inverters. (3 PW2s, 2 inverters, 19Kw solar panels)

I hope this makes sense because I am right now looking out our window at a second snow storm that started a couple hours ago....making ice for my Gin and tonics in advance because.... priorities.

Currently PW are at 100% and I will likely manually turn off PW at some point if grid goes off. But I want to know what the right thing is to do.
I will be downloading the data to see what is shows for the outage two weeks ago.

Thx in advance for any help or gin recommendations

 

[power.saver]

I think your best bet is to have a load shedding plan so you know what to disconnect if the PWs get low. At 20% I would turn off all non-essential loads, and at 10% all but maybe your router and fridge. If you can keep the draw to a few 100 watts, 3 PWs will last a long time.

Supposedly the PW will shutdown before it is truly empty so it can try to restart the next day, but this really only works if there is no house load when it tries to turn on. Did you turn off everything except your inverters when you restarted the PWs? Too much load in a low state of charge may not let them restart and form a grid for the inverters. Also, since it was snowing, cold temps could affect the ability of the PW to come on. In this case, I would try to keep them on with absolute minimum load overnight so you don't get into the restart situation.

 

[BGbreeder]

I would second @power.saver's suggestions on how to minimize load for maximum duration. And, yes, of course, turn on Stormwatch when you expect a storm.

Normally, powerwalls reserve enough power to try several time per day to restart. It might be the case that your powerwalls got colder and the charge level dropped below the magic level for restarting.

There is a procedure detailed elsewhere on the site for jump starting "dead" powerwalls using a 9v or 12v battery on the gateway, with the caveat that solar power needs to be available. The procedure is slightly different depending on which model you have.

All the best,

BG

 

[miimura]

Also there are "Jump" pins in the Gateway. If your PWs have shut down but the sun is shining, you should be able to cold start them with 12V across the Jump pins. Be sure to turn off all your load breakers before jump starting and leave them off until the PWs have gained some charge.

 

[jrweiss98020]

How about turning off ONE of the PWs at 20% or so?

 

[solarAddict]

I would second @power.saver's suggestions on how to minimize load for maximum duration. And, yes, of course, turn on Stormwatch when you expect a storm.

BG

Is there a benefit of not having "StormWatch" turned ON all the time? I sat it and and forget.

 

[ucmndd]

Is there a benefit of not having "StormWatch" turned ON all the time? I sat it and and forget.

Some people prefer to keep it turned off to eliminate the possibility of Powerwalls charging from the grid during peak hours on a time of use plan, which could be quite expensive.

 

[solarAddict]

Some people prefer to keep it turned off to eliminate the possibility of Powerwalls charging from the grid during peak hours on a time of use plan, which could be quite expensive.

Ah, I see. Make sense then. We don't have those here.

 

[sunwarriors]

Is there a benefit of not having "StormWatch" turned ON all the time? I sat it and and forget.

I turned off StormWatch (at least the Enphase version of it) recently and plan to not use it now. As mentioned, you may not want to charge the batteries at peak hours and sometimes, you may not even need it even factoring on-peak rates.

I had it enabled prior and one night at 3am or something, it kicked on. It's amazing how fast the batteries can charge when it's on. I think it hit 100% in a little over an hour (batteries weren't empty though when it activated) so it's extremely fast when needed, but that day was mostly sunny actually so it was unnecessary.

Since I look at tomorrow's weather daily, as long as there is sun the next day ("The sun will come out, tomorrow...." ), charging up batteries is not an issue, power outage or no power outage.

Probably when I don't monitor it so often, having it on is just good insurance, but I think most people are better off just setting a high reserve since you have a lot of people complaining about storm watch not activating and there was a power outage afterwards.

 

[BGbreeder]

Is there a benefit of not having "StormWatch" turned ON all the time? I sat it and and forget.

I do have it on all the time, but I just wanted to be clear that you need to have it on to avoid the behavior experienced by @VABarb. For us the small added cost of charging during peak rates is worth have full batteries going into a weather or fire event.

All the best,

BG

 

[BIC1]

Would this be true for AP Systems microinverters, they need power from the grid or Powerwall to turn on? One more disappointment in the Powerwall system.

 

[ucmndd]

Would this be true for AP Systems microinverters, they need power from the grid or Powerwall to turn on? One more disappointment in the Powerwall system.

Any grid-tie inverter needs to be able to detect a 60hz sine wave - from the grid or something else generating it like a powerwall - to come online and start producing energy. It’s a safety feature present in every grid tie system. As others have pointed out, the powerwall system is supposed to be pretty good at dealing with this and keeping enough power reserve to kickstart itself in the worst case scenario.

 

[WABarb]

I would second @power.saver's suggestions on how to minimize load for maximum duration. And, yes, of course, turn on Stormwatch when you expect a storm.

Normally, powerwalls reserve enough power to try several time per day to restart. It might be the case that your powerwalls got colder and the charge level dropped below the magic level for restarting.

There is a procedure detailed elsewhere on the site for jump starting "dead" powerwalls using a 9v or 12v battery on the gateway, with the caveat that solar power needs to be available. The procedure is slightly different depending on which model you have.

All the best,

BG

Thanks , I will find the jump start pw procedure. That would have worked because solar panels were cleared and sun was out. We had the house wired so we have two circuit panels - one that is backed up with PW and the other that is just grid. We can turn off breakers within the PW backed panel to reduce load.

 

[WABarb]

Is there a benefit of not having "StormWatch" turned ON all the time? I sat it and and forget.

I don't think so . The only reason would be if your area has lots of StormWatch, warnings that don't impact power. After totally running out I think the benefit would out weigh the risk. Particularly during cold weather when you need heat. Mine is now on all the time.

 

[WABarb]

Some people prefer to keep it turned off to eliminate the possibility of Powerwalls charging from the grid during peak hours on a time of use plan, which could be quite expensive.

Pretty sure my PWs are set up to only charge from solar and not Grid so this is not a factor for me.

 

[solarAddict]

I don't think so . The only reason would be if your area has lots of StormWatch, warnings that don't impact power. After totally running out I think the benefit would out weigh the risk. Particularly during cold weather when you need heat. Mine is now on all the time.

Here is a possible reason I was not aware of as we don't have peak rate in my area:

Some people prefer to keep it turned off to eliminate the possibility of Powerwalls charging from the grid during peak hours on a time of use plan, which could be quite expensive.

 

[WABarb]

Also there are "Jump" pins in the Gateway. If your PWs have shut down but the sun is shining, you should be able to cold start them with 12V across the Jump pins. Be sure to turn off all your load breakers before jump starting and leave them off until the PWs have gained some charge.

To turn off PW to preserve power for restart when solar is available - Is it best to just use switch on sides of PWs? And then stagger startup load using breakers in my electrical panel?

 

[solarAddict]

Pretty sure my PWs are set up to only charge from solar and not Grid so this is not a factor for me.

if your PW are indeed setup this way the StormWatch would not work for you in general - the whole purpose of SW give you an ability to charge PW from grid - because of possibility of future interruptions.

 

[ucmndd]

Pretty sure my PWs are set up to only charge from solar and not Grid so this is not a factor for me.

Most people have PWs configured this way because it's a requirement of the tax credit. However, Storm Watch is intended to be the exception to this rule, allowing grid charging for adverse events.

 

[Enginerd]

Pretty sure my PWs are set up to only charge from solar and not Grid so this is not a factor for me.

When Storm Watch is not active, the PWs charge on solar only. When Storm Watch is active, the PWs rapidly charge from the grid until full. Difficult to imagine such frequent & expensive Storm Watch events that one would intentionally disable it. It's the small price one pays for a good insurance policy.