New Powerwall experiences

[oleboyredw]

Hi All,
I had a Powerwall 2 installed on Nov 23rd along with SunPowr solar panels and Solaredge Inverter. I appreciate is possibly not a good time to do it, however it took months to get DNO approval as we were above the 4Wh 'notification' line at 5kWh. Located in Derbyshire, UK. Needless to say I was very busy in the run-up to Christmas and much as I should have been learning I let it slip until now. My background it IT before retiring has led me to wanting to monitor everything. hmm.

Solaredge seems to have some good reporting but of course it does not see everything so I am reliant on what the Tesla app tells me as I cannot find an API or any better reporting.

Maybe I'm doing this all wrong but I have two current 'problems' and the following points sum up the situation.
1: I'm baffled by the difference between Advanced Balance and Advanced Cost Saving. For me I'm struggling to find a significant difference in the way it behaves.
2: To start building up a profile of how my system is performing I collect the information from the app for yesterday first thing in the morning. I discovered that it cant add up! If I look stats for 3rd Feb app and select solar it reports 0% of output to grid, yet if I then look at the grid it shows 2.7kWh to grid. Other numbers look OK, but what other traps are there.
3: In part of the world we've seen a really nice sunny day followed by a few bad days. That seems to result in the battery not charging from grid overnight and us taking some peak rate energy towards the end of the day. Is there a way I can force it to top up overnight? I cant find one.
4: To add to the confusion we have only two different tariffs, low and high. low times are 22:30-00:30 and 02:30-07:30. I think I can only have one low tariff time so I've set it to 02:30-07:30. That high tariff from 00:30-02:30 is a pain, if I were cynical I'd say it was to trip users up and get them to put stuff on overnight ... at peak charge.

The problems:
1: How do I monitor this system automatically without having to key in loads of data daily from an app that looks all very nice but might just have a maths problem?
2: Is there a clear doc that explains how the management works such that I can check I've got it configured correctly (not that there is a lot you can do)?

 

[Neil_dsb]

Q3 is the biggest problem, last night our PW only charged to ~20% following a sunny day previously, it was empty by 10am....as you noted the UK is rather unpredictable....I wish there was a manual present charge or override...

We use power save mode and it discharges during peak power on our economy 7 rate.... except this morning when I preheated the model X and it started discharging during off peak? Most of the time it works....hope this helps?

 

[wbhokie]

3: In part of the world we've seen a really nice sunny day followed by a few bad days. That seems to result in the battery not charging from grid overnight and us taking some peak rate energy towards the end of the day. Is there a way I can force it to top up overnight? I cant find one.

One thing I'm pretty sure of, is that the battery will never charge off of grid power if you have a solar-connected system, it will only charge off of solar power. So no... AFAIK, you cannot force it to top off.

 

[Neil_dsb]

One thing I'm pretty sure of, is that the battery will never charge off of grid power if you have a solar-connected system, it will only charge off of solar power. So no... AFAIK, you cannot force it to top off.

Yes we have a solar array and we charge from the grid during the off peak night

 

[wbhokie]

Yes we have a solar array and we charge from the grid during the off peak night

My mistake, I guess if you have a TOU plan then it operates differently. I was mis-informed.

 

[MorrisonHiker]

My mistake, I guess if you have a TOU plan then it operates differently. I was mis-informed.

@Neil_dsb is in the UK. Tesla does allow Powerwalls in the UK, Australia and other countries (?) to be charged from the grid.

 

[cwied]

Just to add: the grid-charging restriction with solar is as far as I know solely a US feature to preserve eligibility for the federal tax credit. In other countries, there is no such restriction.

 

[JohnRatsey]

I'm in England and have off-peak charging working using the Cost saving option of Advanced tie-based control with the off-peak period defined using Edit Price Schedule. I can't remember if I had to ask Tesla support to enable anything. My grumble is that Tesla's algorithm uses historical data and no solar generation forecast so it gets caught out by a sunny day following some cloudy ones (too much charging to absorb the spare power when the sun shines) or conversely a low output day (and snow = zero) after some relatively good ones. Evidently Tesla's developers have never experienced British weather but the more of us who request better control over the charging then the more likely that something will be done. My work-around for the first problem is to limit the off-peak period in the Tesla app.

I'm using PVOutput for the data collection. An excellent guide to setting it up is here and the AU$20/year charge is well worth it due to the time-based graphics. You should be able to see my PW data here if you click on the right-most blob under the date which enables the extended data. The software to interrogate the PW is running on a cheap Windows tablet which records one minute data (should I ever want to get into more detail) while 5 minute data gets uploaded. You'll see that my PW has a relatively easy life.

 

[JCUK]

JohnRatsey, you were lucky my powerwall left me using the grid from 2pm today with no hope of any solar generation for the rest of day. Yesterday it stopped at 9am but the sun came out later and saved the day.

I would give you a thumbs up if I knew how to.

 

[JohnRatsey]

JohnRatsey, you were lucky my powerwall left me using the grid from 2pm today with no hope of any solar generation for the rest of day. Yesterday it stopped at 9am but the sun came out later and saved the day.

If your off-peak charging isn't working to your satisfaction then contact Tesla support. As noted above, off-peak charging is a region-specific feature which needs to be enabled. I use [email protected] but response to emails is erratic. Phoning might quicker if you are lucky and someone answers.

 

[JCUK]

If your off-peak charging isn't working to your satisfaction then contact Tesla support. As noted above, off-peak charging is a region-specific feature which needs to be enabled. I use [email protected] but response to emails is erratic. Phoning might quicker if you are lucky and someone answers.

I have contacted them on a number of occasions, but no success yet. It does charge offpeak but most of the time up to 20%.

 

[oleboyredw]

So, charging from grid works but is not ideal for me based on my (only two months) winter experience. It would be nice to be able to force a top-up.

Anyway, it’s been running on Advanced/Cost Saving. Two days ago I changed to balanced. Bad idea, it stopped charging from grid in cheap time. Back to Cost Saving next day.

 

[Solar1920]

I've got a powerwall on order, but am getting increasing apprehensive with all the issues and problems that powerwall owners seeem to be experiencing with the Powerwall control algorithum. I'm in the UK so will be dependent on it during the winter months for TOU.

JohnRatsey - I've been having a look at your usage on pvoutput and you pretty much seem to have your setup working well, like you say your usage is quite light but all the days i looked at you had the mixture of cheap rate electricity and solar working about right, so no peak rate electricity was ever used.

Have you found the algorithum works for you or are you having to constantly fettle with it to achive the results you want? What ever your doing you seem to have it sussed out.

 

[Maximapolak]

One thing I'm pretty sure of, is that the battery will never charge off of grid power if you have a solar-connected system, it will only charge off of solar power. So no... AFAIK, you cannot force it to top off.

Outside the US it's allowed.

 

[JohnRatsey]

I've got a powerwall on order, but am getting increasing apprehensive with all the issues and problems that powerwall owners seeem to be experiencing with the Powerwall control algorithum. I'm in the UK so will be dependent on it during the winter months for TOU.

JohnRatsey - I've been having a look at your usage on pvoutput and you pretty much seem to have your setup working well, like you say your usage is quite light but all the days i looked at you had the mixture of cheap rate electricity and solar working about right, so no peak rate electricity was ever used.

Have you found the algorithum works for you or are you having to constantly fettle with it to achive the results you want? What ever your doing you seem to have it sussed out.

After 11 months with the PW I've reached the following conclusions:
1. May to September inclusive there's normally enough solar generation (nominal 4kW array) that, with my usage, the battery wasn't emptied (April may now be included since last year's data predates a serious haircut to a tree which was causing some shading). With the capacity exceeding daily usage there's some carry-over from a sunny day to compensate for a cloudy one.
2. Tesla's off-peak charging algorithm is based on solar generation and usage for the past few days and doesn't consider any weather forecast (it must have been developed by someone who hasn't experienced British weather). Consequently the charging gets increased as a consequence of a few cloudy days and then the battery doesn't have the capacity to absorb the generation on a sunny day.
3. There's no direct user control over the amount of off-peak charging (I've asked for user-defined charge limits to be provided but there's no sign of anything forthcoming).
4. However, I've figured out that the charging can be restricted by reducing the off-peak period in the Tesla app. My PW has the 16A discharge limit as I don't have the permit from the grid operator to discharge more (a bit of nonsense since the PW should only discharge in response to household demand and not discharge to the grid). This current limit also appears to apply to the charging which works out to be 22% per hour. I'm therefore adjusting, every evening, the off-peak period to reflect what charging I think needs to be done based on the weather forecast and current state of battery charge. I got it wrong last evening: The weather forecast suggested a similar sun / cloud mix as on the previous day but there's been noticeably more sun mid to late morning so the generation has been a lot more and by noon the battery was full.
5. Unfortunately, there's currently no way to force the PW to increase the off-peak charging by more than it thinks appropriate in anticipation of particularly poor solar generation (mid-winter murk or a bit of snow on the panels).
6. A small amount of peak rate electricity gets used when household demand exceeds the output of battery+solar. This tends to be for short periods (eg the kettle) which often doesn't get reflected in the PVOutput data.
7. I'm currently on an Economy 7 tariff with Octopus. However, before next winter I'll be asking if it's possible to shift to their Go tariff which is aimed at EV charging and limits the cheap power period to 4 hours but it's currently about 60% of the cost of E7 off-peak.

I hope this helps!

 

[Solar1920]

It does help thanks, I kinda guessed that was what you were doing. It would be good to have a bit more manual control, but I read somewhere that the Tesla software developers were from Apple, so “manual” is probably not in their vocabulary.

 

[oleboyredw]

Despite my comments about the experience so far I’ve been very happy on the whole. Install date was 23rd November for me and I’d expected not a lot to be generated over the winter oeriod. I’m still learning and definitely glad I went for a solar PV install and glad I added the battery. I’ll put some simple stats here in the morning when I update my spreadsheet.

 

[JES2]

Despite my comments about the experience so far I’ve been very happy on the whole. Install date was 23rd November for me and I’d expected not a lot to be generated over the winter oeriod. I’m still learning and definitely glad I went for a solar PV install and glad I added the battery. I’ll put some simple stats here in the morning when I update my spreadsheet.

I've been happy with my PW2s, but I can't seem to consistently get the Powerwalls to act correctly in "off peak". They should not be producing energy during "off peak", but for some reason, they come on after I have charged them up during a sunny day. It works fine for a couple of days, but then, they decide to not turn off once "off peak" hits.

I can remedy this by changing the "reserve for power outages" up high enough to force the Powerwalls to shut down. However, that takes at least an hour before the Powerwall accepts the change. That, too, seems to be odd, that it takes an hour to get a Powerwall to make an adjustment.

I have been working with the Tesla Power folks for the last couple of weeks. We thought we had the problem solved until this latest occurrence.

 

[cwied]

When working normally, Powerwalls respond to app changes only once an hour. This seems to be intentional on Tesla's part, because if you use the local setup wizard, the Powerwalls will happily change modes immediately. My speculation is that Tesla did this to discourage users from making manual changes because they would like to have more control over the Powerwalls themselves. I think this might make it easier for them to offer grid stabilization services later on.

 

[JohnRatsey]

It does help thanks, I kinda guessed that was what you were doing. It would be good to have a bit more manual control, but I read somewhere that the Tesla software developers were from Apple, so “manual” is probably not in their vocabulary.

Something else I should have mentioned is that I'll need to switch back to Balanced once there's enough solar power, on average, to meet the household demand. Otherwise the battery will likely do some off-peak charging when there's been a cloudy day or two. The minimum off-peak duration allowed by the app is 1/2 hour.

Also, as commented above, the battery software tends to discharge during the off-peak period if it's not charging although I've occasionally it will go onto standby. Sensibly, if it sees a need for off-peak charging then the round-tripping of power can be minimised by going into standby during the off-peak (with the amount of charging then reduced). Unnecessary round-tripping both costs money and increases the battery wear. Maybe we'll see some improvements before next winter as the Australians also use the off-peak charging and appear to be more numerous so more likely to grab Tesla's attention.