powerwall time based control working?

[kuruma]

Does anyone else suffer from your powerwall not figuring out how much energy you might need in the next 24 hours on the time-based control setting?

For example, we switched to time-based the other night because the weather looked grim the next day. When we woke up, we had a grand total of 19% in the tank. It poured with rain all day. We ran out of power sometime after lunch and went to the grid. In the evening, there was not one, but four separate power cuts all of which we would have been protected from had the powerwall given us more power to start with and had we not had to use up all our powerwall during the day (yes I know we could have held some in reserve but power cuts are so infrequent...)

The very next night, having left it on time-based control, we woke up to sunny weather (most of the day) and our powerwall on 90%! We spent the day doing all we could to use up our excess solar.

This is so frustrating and the only way we've figured out to get round it is when one of us tootles to the loo after midnight, we switch the powerwall reserve amount to something like 50% to ensure that we have at least what we need for the next day. Otherwise, there's no telling what it might give us for our energy needs. (Oh... and then we have to remember to turn that down the next day or it shuts off at 50%!)

Are we doing something wrong?

 

[Dilly]

It’s not a complete control, but if you see that coming again, crank up the back-up reserve to a point where it will drop below the threshold early on in the cheap rate window. It should then fill pretty much.

 

[Gatsojon]

Have you tried the reduced cost mode? That’s what I used before switching to the Tesla Tariff. It didn’t always get it right but wasn’t too far off once settled in. I’m assuming you are on Go and have set the cheap period up.

im thinking I might switch back to Go now the solar is reducing and my mileage might be increasing again.

 

[PITA]

I had exactly the same problem ...

We have two Powerwalls (27kWh storage), installed in April 2021 (UK Based).

Initially we were 100% self powered (7.2kWp Solar Array) and this went on for weeks in Self Powered mode. So it all worked great.

However, as the weather changed I started to experience the same as you. Not charging enough, then over charging when sunny next day. But I was manually flicking between modes all the time.

The problem is you're switching between Self Powered & Time Based Control and the AI Can't get a grip on your history pattern or whats needed.

I was told to put it on Time Based Control and leave it alone. Yes a few days will be inefficient whilst it sorts itself out... but now I find it's cleverer than me. It gets it right most of the time as well, which is good because I don't get involved anymore.

The second issue I had, was my installer had capped out charging speed to 5kW... which was DNO conditional before we upgraded our cabling infrastructure (which we did). So once that had been derestricted, by Tesla, we were able to charge from the Grid at full power again. Having only a 4 Hour window overnight, this made all the difference.

Now we can download at up to 18kW for EV & Powerwalls for 4 hours straight. Great

Today... Charged the car to 90% .... filled up the Powerwalls as its raining today. All automatically.

It pulled in 40kW in that 4 hour window. Cost me £2 on Octopus Go and that'll do nicely for today

 

[PITA]

Just to add...

Our house is quite high useage as we're pretty much all electric, and have air conditioning. So we can go through a fair bit if the Sun comes out unexpectedly. Or charge the car a bit more.

So we tend to ramp up house demand on Sunny days anyway... washing, drying, cooking etc

 

[scdoubleu]

Does your house have a 3-phase supply, given the combined capacity of your solar and PowerWalls?

We've just recently pulled the trigger on panels and a PW2 for installation in the next few weeks (PW likely installed at a later date when they finally have some in stock). We have roof space for just over 9 kW of panels, but the DNO (Western Power) dug their heels in and will permit no more than 6 kW solar, with PW limited to 3.68 kW output. We're also high users, like yourself; 3 x ASHP, 1 x EV, but on a single-phase.

Steve

 

[PITA]

Does your house have a 3-phase supply, given the combined capacity of your solar and PowerWalls?

We've just recently pulled the trigger on panels and a PW2 for installation in the next few weeks (PW likely installed at a later date when they finally have some in stock). We have roof space for just over 9 kW of panels, but the DNO (Western Power) dug their heels in and will permit no more than 6 kW solar, with PW limited to 3.68 kW output. We're also high users, like yourself; 3 x ASHP, 1 x EV, but on a single-phase.

Steve

Yes... ours was a nightmare.

Our DNO (Western Power) came onsite originally and discovered we had a looped supply.

This meant we couldn't get authorisation for an EV Charger until our cabling had been upgraded to a direct power feed. With Covid lockdown restrictions, staff shortages & backlogs it took MONTHS...

Whilst we were chatting, I cheekily asked for a 3 Phase supply (considering all that we had planned), and they agreed to upgrade and do it free of charge. It took about a week and the whole street was dug up. They reckon it cost them between £7,500 - £10,000

Now we have installed:

- 3 Phase Hybrid Cabling & Supply
- 7.2kWp solar array (but limited by a 5kW inverter)
- 2 x Powerwall 2 batteries & Gateway 2 (unlimited charge rate, 10kW discharge constant)
- 7kW Zappy Charger & Tesla Model 3 Performance EV
- 8kW Toshiba Haori Heat Pump (air to air) climate air conditioning
- 3kW Eddi Solar Water Heater
- 7kW Induction Hob

The 7kW Zappy car charger is wired directly into the Tesla Gateway 2 device, so avoids going through the Consumer board

This is what our house is doing this morning...

 

[scdoubleu]

Lucky sod! The DNO's 3-phase cable comes down our drive, but ends about 8m from the house, with single-phase runs to us and a neighbour .

Steve

 

[PITA]

Lucky sod! The DNO's 3-phase cable comes down our drive, but ends about 8m from the house, with single-phase runs to us and a neighbour .

Steve

Haha, I didn't feel lucky at the time my EV Charger was denied... and then months of delays.

But, yes... it turned out 100% very lucky.

 

[PITA]

.... In the evening, there was not one, but four separate power cuts all of which we would have been protected from had the powerwall given us more power to start with and had we not had to use up all our powerwall during the day (yes I know we could have held some in reserve but power cuts are so infrequent...)

Not sure what date that was, but on September 10th, we had SEVEN micro-blackouts...

Weird...

 

[kuruma]

well our blackouts were all in the evening. Wouldn't really have cared if they were in the wee hours as yours were. Turned out a transformer in a nearby village was having itself a barbecue.

Anyway, we're on single phase and can't get on the Go tariff because we can't have a smart meter (don't get me started) because there's an RAF base within 400 miles (or some such rubbish).

I'll take PITA's advice, switch it to time-based and give it a week to see if things improve. I get how the AI would be confused by our micromanaging.

 

[SpareHeadOne]

As others have noted you need to leave the thing to work out your usage pattern, then it mostly gets it right - although for some reason Tesla don't seem to be able to check the weather for the upcoming day and use that to predict the solar generation.

I have found that if you run something high usage (e.g. dishwasher, washing machine) towards the end of the cheap rate window then the PW will often be fooled into thinking you're going to have a heavy day and will charge up a bit more if it's on the low side.

 

[kuruma]

we ran the dishwasher to finish at 7am. We ended up with 10% on the powerwall which we've set as a reserve so we're drawing from the grid for breakfast

...

sigh

it is forecast to be sunny over the next couple of days though so that should kick in very shortly.

 

[PITA]

we ran the dishwasher to finish at 7am. We ended up with 10% on the powerwall which we've set as a reserve so we're drawing from the grid for breakfast

...

sigh

it is forecast to be sunny over the next couple of days though so that should kick in very shortly.

Be patient

Once it knows you're having to draw from the Grid, it'll start writing notes in it's diary

Just to add to your temporary misery... I find TWO Powerwalls are perfect

 

[kuruma]

au contraire... not only would two powerwalls very much screw up the amount of space we have left in our garage, it would be far more expensive to add another one than I could spend on peak price energy in the remaining years before my life expectancy is reached.

 

[Dilly]

we ran the dishwasher to finish at 7am. We ended up with 10% on the powerwall which we've set as a reserve so we're drawing from the grid for breakfast

...

sigh

it is forecast to be sunny over the next couple of days though so that should kick in very shortly.

If I think that predicted use is going to breach the reserve overnight, I increase the reserve so that the use comes off the grid at cheap rate as well as filling the Powerwall sufficient for the next burst of sunshine. Then I drop it back.
a second Powerwall won’t pay for itself but it’s a warm cosy feeling!

 

[mnobleuk]

I'm trying to do some man maths to justify battery storage without solar (our site is very bad for solar) - we use approximately 20kWhs a day (which I think on average 5 are for car charging), given we use some electricity overnight I think a single powerwall would power us on off peak electricity for a full day. (20 - 5 (car could charge overnight) - ?5 overnight use)

Being in NI smart tariffs aren't available - I currently pay 20p per unit. Economy 7 is 10p per unit so using a powerwall would halve our bills (currently about £1200 pa (lots of kids, me homeworking, wife who worships the tumble dryer etc etc) - so I could save £600 p.a.

The tesla site quotes £8700 for a powerwall so payback at current prices would be 14.5 years, or if prices rise by 5%pa 12 years (or nightmare scenario 10% a year = 10 years)

While there are cheaper systems which would payback earlier as a tech head there are lots of things about the powerwall I like - so essentially I look at it like I'm getting a whole house UPS for "free"

The big question is - how much are the installation costs ? It strikes me that it's not that complex.
Also - I'm I missing something ? Are there snags around how long the batteries charge (being too long for off peak electricity), or the inverter not being able to power everything at once ?

I'm very interested in your experiences (and reasoning for buying)

 

[PITA]

I'm trying to do some man maths to justify battery storage without solar (our site is very bad for solar) - we use approximately 20kWhs a day (which I think on average 5 are for car charging), given we use some electricity overnight I think a single powerwall would power us on off peak electricity for a full day. (20 - 5 (car could charge overnight) - ?5 overnight use)

Being in NI smart tariffs aren't available - I currently pay 20p per unit. Economy 7 is 10p per unit so using a powerwall would halve our bills (currently about £1200 pa (lots of kids, me homeworking, wife who worships the tumble dryer etc etc) - so I could save £600 p.a.

The tesla site quotes £8700 for a powerwall so payback at current prices would be 14.5 years, or if prices rise by 5%pa 12 years (or nightmare scenario 10% a year = 10 years)

While there are cheaper systems which would payback earlier as a tech head there are lots of things about the powerwall I like - so essentially I look at it like I'm getting a whole house UPS for "free"

The big question is - how much are the installation costs ? It strikes me that it's not that complex.
Also - I'm I missing something ? Are there snags around how long the batteries charge (being too long for off peak electricity), or the inverter not being able to power everything at once ?

I'm very interested in your experiences (and reasoning for buying)

Ok... something very important here to factor in...

Discharge Capability

A single Powerwall 2 can only discharge continously at 5kW

This means if your house is demanding say 1kW ... all is fine. The house will then take 1kW from the Powerwall cheap stored electricity.

However, if you then turn on an 8kW electric shower... your house is now demanding 9kW in total.

A single Powerwall can only supply 5kW... so the other 4kW has to come from somewhere else (Solar Array or Grid Power).

If it comes from the Grid, it'll usually be right in the Peak Rate daytime period.

Now... importantly, if you're in a blackout situation without Solar, any demand above 5kW will SHUT DOWN your Powerwall as it can't go above 5kW ... so you could be no better off, unless you stop people turning on high demand items (kettles, cookers, showers, dryers, heaters...)

So....

The reason I have TWO Powerwalls is because my discharge capacity is now 10kW... plus our Solar Array generation.

This gets us through our day pretty much self powered for the home. In fact, from April to June 2021 we were 100% self powered until the crappy weather hit.

Two Powerwalls can bridge us over two days of bad weather before we have to go back to the Grid for top ups. (none of the above includes car charging)

 

[PITA]

... just to add...

A Powerwall is just storage. If you want backup against Grid Outage, you also need a Tesla Gateway 2...

We have a Gateway 2 on our house (why wouldn't you??) and it's absolutely brilliant.

When the street has a Blackout, Tesla Gateway 2 islands your home automatically and you run about excitedly like a 5 year old while your Wife rolls her eyes at the specticle of you... that's if you even notice the Smartphone backup notification.

... and your house remains automatically powered up while your neighbours hate you so much... such a nice feeling

 

[ACarneiro]

I’ve not had a power cut since installing my PWs. Damn it.