What happens when the powerwall runs out of power?

[fresnoboy]

Hi everyone. I'm still trying to understand the behavior of the system as I try and see if getting a set of powerwalls makes sense for me, esp if I use them instead of a generator for backup.

In the normal self use optimization mode and backup modes, what happens if the powerwall runs out of power at night when the inverters are not on and if the grid is down?

In the generator thread, the behavior outlined was that when it hits zero, the system shuts off and doesn't come back on until the grid power is restored. This makes sense, since the solar inverters won't turn on unless they see power, and if the powerwall is discharged, then there is no power available to signal to the inverters to turn on, even if it's really sunny outside.

If there was a reserve value that triggered a shutdown when reached, potentially the powerwall could come back online at a time when it would be thought to be sunny to try and trigger the inverters, but the way it appears these systems are wired, the house loads would also be attempting to consume power from the powerwall, and it may not be able to support that while the inverters are coming back online.

If the inverters and the powerwall could be disconnected from the house completely, a small reserve amount of charge would all that would be needed to kickstart the inverters, and then the house could be reconnected when the powerwall was charged to a certain point. But I don't think the gateway is wired like that, is it?

When TOU shifting becomes available, it would seem this would be even more an issue if a power outage happened towards the end of the peak period, and the powerwall had sent most of it's energy to the grid for that day. It would switch to supporting the house's load, but if it ran out of energy, and and the grid was still out the next day, I don't see how it would restart the inverters and you would be oout of power until the grid came back.

Can someone who actually has one of these tell me what happened if the PW shutdown during an outage? Does it get the inverters to come back online somehow the next morning?

My apologies if I have missed something obvious.

thanks!
mike

 

[eml2]

In 1.11.2, there is always a 2-3% reserve left in the PW, even if you set to 0% reserve in the app. i.e. there is a 2-3% discrepancy of the PW SoC between the app and the Web UI. So, when there is outage and PW is drained, it still has ~2% left. Then, the next sunny morning, power cycle PW and it should be able to turn on PV inverter.

This was told by Tesla support. I haven't tried it myself.

 

[nswfugitive]

If the grid is down and solar is not being produced - and your battery runs dry everything in the house shuts down. Just like if you only had the grid and the grid goes down. Of course if you want to prolong the battery you can turn off appliances or circuit breakers on the phase your battery is attached to.

 

[Tam]

...it ran out of energy, and and the grid was still out the next day...

That's why you don't buy just 1 powerwall for this situation. Buy MULTIPLES!

 

[fresnoboy]

In 1.11.2, there is always a 2-3% reserve left in the PW, even if you set to 0% reserve in the app. i.e. there is a 2-3% discrepancy of the PW SoC between the app and the Web UI. So, when there is outage and PW is drained, it still has ~2% left. Then, the next sunny morning, power cycle PW and it should be able to turn on PV inverter.

This was told by Tesla support. I haven't tried it myself.

Interesting, so you have to do it manually? No way to set a timer or take input from a signal of some sort?

Can you program in a reserve so it would shut off at 15% or 10% instead running almost all the way down?

Can you power cycle the powerwall from the app if the network connections are still powered up via UPS of some sort?

thx
mike

 

[fresnoboy]

That's why you don't buy just 1 powerwall for this situation. Buy MULTIPLES!

This is always about statistics. If you have an outage during really rainy weather with little sun, or someone in house does something that burns a lot of power without realizing what's going on, you are going to still have situations where you will run out of power. More PW's reduce the odds of that happening, but you can't guarantee it will keep going without a shutdown event.

 

[Shygar]

It should be easy for someone to try. Flip your main breaker then run your powerwall out while it is dark. Then see if the solar starts working the next day. As mentioned, with the unreported and built in 2-3% I would suspect there would be enough power on the powerwall even when the app reads "zero" for it to kick on the solar the next day. But I saw a vampire drain of around 1% a night so if you had a few days of no sun, you may not have enough power.

 

[strider]

Interesting, so you have to do it manually? No way to set a timer or take input from a signal of some sort?

Can you program in a reserve so it would shut off at 15% or 10% instead running almost all the way down?

Can you power cycle the powerwall from the app if the network connections are still powered up via UPS of some sort?

thx
mike

The PW would have no way of knowing if the solar panels had sun on them. The inverters are shut down due to having lost "the grid". You could potentially rig up something with a light sensor on your roof and some kind of a relay...

You can set the reserve to be higher to give you more buffer.

If the PW shut down due to hitting its reserve your house is dark. I believe you'd have to physically power cycle it.

What's the use case of you not being home during a power outage and running the PW down overnight? If you're not home your A/C should be off and heat should be set as low as it can go. What's running at an unoccupied house to burn through that much power?

 

[fresnoboy]

The PW would have no way of knowing if the solar panels had sun on them. The inverters are shut down due to having lost "the grid". You could potentially rig up something with a light sensor on your roof and some kind of a relay...

You can set the reserve to be higher to give you more buffer.

If the PW shut down due to hitting its reserve your house is dark. I believe you'd have to physically power cycle it.

What's the use case of you not being home during a power outage and running the PW down overnight? If you're not home your A/C should be off and heat should be set as low as it can go. What's running at an unoccupied house to burn through that much power?

Well, first off, I travel quite a bit, and I don't want my wife having to try and figure this out if I am not home. Secondly, I am a software engineer, and have a rack of servers that burn about 2kw's on a more or less continuous basis. Some of that will power down in an extended outage, but again, it's not something I want my wife having to figure out.

I will have a ton of solar in the new house, so production shouldn't be a problem.

One or two PW's would not be enough for my needs, but 3-4 might work. But if one PW is rebooted, and the inverters start, do the other PW's automatically detect that and power on, or would I (or my dear wife) have to power cycle all of the?

Generators have nice automatic transfer switches that make all this easy, but hopefully Tesla will figure things out and make it more user friendly. If the system wasn't so closed, it would be easy to wire up a solution. But such is not the case...

thx
mike

 

[Dot_]

This is happening to me right now, so here is an accurate response to your question, not a guess!

Your question: What happens if the powerwall runs out of power at night when the inverters are not on and if the grid is down?

My current situation:

In brief: I have no power rn as the grid is down (for maintenance) and my batteries are completely empty after 3 days of cloudy rainy skies and high energy use. I can't recharge them from my solar as I let the batteries run completely empty.

More detail:

Property: Medium sized farm in Northern England with constant power requirement of AT LEAST 2-3kw, 24/7.
Power supply: Three phase power supply from the grid, 62 solar panels, 3 tesla powerwalls.

Our 3 powerwalls ran out of power early this morning after 3 days of very low power input due to rainy overcast days and lots of power use here at the farm. This was not a problem as we are also connected to the grid - HOWEVER - the grid turned off this morning for some maintenance work (it will be back on in a few hours) and when the grid turned off, our batteries were COMPLETELY EMPTY.

The good news is that THIS SITUATION IS EASILY AVOIDABLE! Here is how not to be a lemon like me:

- On the Tesla app you can click 'settings' > 'powerwall.' Here you can set the 'Backup Reserve' from 0% - 100%. On the app the lowest recommended backup reserve is 20%. Because I couldn't help but tinker with the settings (damn you curiosity!) I changed the recommended settings to 0% recently, meaning my powerwalls ran themselves completely dry in the early hours of this morning just before the grid connection cut off, leaving us with no mains power, no sunshine as it was still dark and empty batteries. Doh!

I reassured my better half and family that my fabulous new renewable power system would be up and running again as soon as the sun came out. Luckily its a beautiful sunny day! BUT GUESS WHAT - it doesn't matter how sunny it is as it turns out (info sourced from my electrician) if there is no power from the grid or batteries to power the inverter you can't make any power from your solar to refill your batteries. You need to always keep a bit of power in the batteries to run the inverter for the solar.

So I'm sat here in the beautiful sunshine writing this while all my solar panels are sat idle, my batteries aren't filling up and IT SUCKS!

To conclude: Don't set your backup reserve to 0% if you need to run an inverter for solar panels.

Yours Sincerely,

First class Tinkering Lemon

p.s - I now don't regret tinkering as it allowed me to answer this question from first hand experience and understand for myself what my system would do if the batteries were empty and there was no power from the grid. Every day is a school day!

 

[jjrandorin]

This is happening to me right now, so here is an accurate response to your question, not a guess!

Your question: What happens if the powerwall runs out of power at night when the inverters are not on and if the grid is down?

My current situation:

In brief: I have no power rn as the grid is down (for maintenance) and my batteries are completely empty after 3 days of cloudy rainy skies and high energy use. I can't recharge them from my solar as I let the batteries run completely empty.

More detail:

Property: Medium sized farm in Northern England with constant power requirement of AT LEAST 2-3kw, 24/7.
Power supply: Three phase power supply from the grid, 62 solar panels, 3 tesla powerwalls.

Our 3 powerwalls ran out of power early this morning after 3 days of very low power input due to rainy overcast days and lots of power use here at the farm. This was not a problem as we are also connected to the grid - HOWEVER - the grid turned off this morning for some maintenance work (it will be back on in a few hours) and when the grid turned off, our batteries were COMPLETELY EMPTY.

The good news is that THIS SITUATION IS EASILY AVOIDABLE! Here is how not to be a lemon like me:

- On the Tesla app you can click 'settings' > 'powerwall.' Here you can set the 'Backup Reserve' from 0% - 100%. On the app the lowest recommended backup reserve is 20%. Because I couldn't help but tinker with the settings (damn you curiosity!) I changed the recommended settings to 0% recently, meaning my powerwalls ran themselves completely dry in the early hours of this morning just before the grid connection cut off, leaving us with no mains power, no sunshine as it was still dark and empty batteries. Doh!

I reassured my better half and family that my fabulous new renewable power system would be up and running again as soon as the sun came out. Luckily its a beautiful sunny day! BUT GUESS WHAT - it doesn't matter how sunny it is as it turns out (info sourced from my electrician) if there is no power from the grid or batteries to power the inverter you can't make any power from your solar to refill your batteries. You need to always keep a bit of power in the batteries to run the inverter for the solar.

So I'm sat here in the beautiful sunshine writing this while all my solar panels are sat idle, my batteries aren't filling up and IT SUCKS!

To conclude: Don't set your backup reserve to 0% if you need to run an inverter for solar panels.

Yours Sincerely,

First class Tinkering Lemon

p.s - I now don't regret tinkering as it allowed me to answer this question from first hand experience and understand for myself what my system would do if the batteries were empty and there was no power from the grid. Every day is a school day!

This is a pretty old thread to necro about this topic, but you should be able to re start your solar + batteries if they are empty.

Best Practices During Power Outages | Tesla Support

Powerwall brings you energy independence and security, so life in your home can carry on uninterrupted when the grid goes down. Learn more about how Powerwall functions during extended power outages.

www.tesla.com