Circular reasoning (Rolfe's solar energy system)

[Rolfe]

Thanks for that, very kind.

 

[Bam Bam]

This is so nuts I still feel I must be missing something, but I've been through every setting I can see, and can't find anything. And I read someone else saying he didn't know how to stop his battery charging on the solar.

Two suggestions that may or may not work.

Discharge:
I also find this very confusing. Maybe it is the opposite of what we assumed it to be. It means 'home support only between these hours' so set this for 4pm-11.30 and you won't draw from the grid during that time.

Export:
What if you try setting an export % during the solar hours?

Set it to export battery (down to, say, 40%) from 8am-4pm.

Not sure if these will work for you, but there are some ideas.

 

[Rolfe]

You have a GivEnergy system too, is that right?

I reversed the "Timed Discharge" to set it from 11.30 till 5.30, but again it didn't make any difference. The house is still taking the solar. (Of course there is no demand on the battery while the panels are generating, as they are at the moment.) I have absolutely no idea what use this setting is. I can only assume that it prevents the house using the battery outwith the time set, but I can't easily imagine why that would be a useful thing to do.

I'm still trying to get my head round the export idea, but I can try something.

ETA. No, that didn't work either. All that happened was that the battery discharged at its maximum rate until it got to the 98% limit I'd set just to see what would happen. This all went to the grid, vastly overtopping the 5 kw export limit I have (so most of it was just wasted), and once the battery got to 98% it stopped. The house went on calmly running on the solar as usual the entire time.

ETA again. I tried disabline "eco", believing that would make the house run from the grid. Not a bit of it. Again absolutely nothing happened. The house went right on using the solar. Baffled now.

 

[johnb80]

Have you considered switching off the solar panels if you want to export and use your battery on a sunny day?

Rolfe wouldn't gain anything by doing this?

 

[Gadget Geek]

Rolfe wouldn't gain anything by doing this?

Yeah, I realise that now. I think the Timed Discharge is the function she wants, it's just getting the setting right. I think if Rolfe sets the Timed Discharge from a time in the morning when the panels start to generate, to 23:30 when the off peak kicks in, that should make the panels export.

Edit: Or even set the Timed Discharge to cover the peak hours so that the battery covers all of the expensive electricity.

 

[Gadget Geek]

Have you seen this video? Charge/Discharge setting is at 15:38. I don't know if this will help.

 

[Rolfe]

Thank you all, most sincerely.

I had a look at the switches on my inverter but they are scary-looking things I will not be touching. There is one for AC and one for DC, and all sorts of warnings, and I think they're for making the thing safe if you need to work on it.

I think the timed discharge should be the thing, but when I tried it, it didn't change anything. But then when I disabled "eco" mode, thinking that would cause the house to switch to mains power only, again nothing happened.

I'm not losing anything at the moment, because I'm recovering what I lose with the house and battery using the solar during the day by exporting the battery in the evening. But that is proving to be a right royal pain in the arse to get right, and it's also irrational.

I need to watch that video.

 

[JackRussell]

I don’t have this system so not sure if you can specify to charge the battery to different percentages at different times of the day or whether you would need to manually change limits in the morning and evening but this is what I have been thinking.

Sometime after 05:30 (ideally before Solar generation) could you set the battery charge limit to say 50%? As the battery will be above 50% when the panels start to generate the solar output will be exported.

 

[Bam Bam]

I don’t have this system so not sure if you can specify to charge the battery to different percentages at different times of the day or whether you would need to manually change limits in the morning and evening but this is what I have been thinking.

Sometime after 05:30 (ideally before Solar generation) could you set the battery charge limit to say 50%? As the battery will be above 50% when the panels start to generate the solar output will be exported.

Yes, this is along the lines of one of my suggestions.

But if you set it to charge up to that amount, then if it is above that (from overnight filling) then it won't drop down to 50%. It will only go up.

So it would be necessary to set it to export down to 50% instead.

 

[Bam Bam]

I expect that soon enough your solar will drop off and you won't be so worried about it. The solar will just top up the battery, which will then get you through until the next evening session.

Then when Spring comes around you can focus on export again.

 

[Rolfe]

Yes, this is along the lines of one of my suggestions.

But if you set it to charge up to that amount, then if it is above that (from overnight filling) then it won't drop down to 50%. It will only go up.

So it would be necessary to set it to export down to 50% instead.

I don't think that would work - though I have been wrong about things before. If the battery is below 100%, and there is more solar than the house needs, then the battery will take that solar. No way to stop it that I can see. Also no way to get the house to use the battery in preference to the solar.

I have watched the video, which I see is a year old. I knew most of it, but he pointed out some screens and some shortcut functions I wasn't aware of. Part of the issue is that he is on Intelligent Flux, so he wants to do things in a different way from me. But the main issue is that the screen where he controls these settings looks completely different from the one on my app. (I checked the app store for an update and there isn't one. My app is the newer version.)

Looking at his version carefully, he has an option to charge the battery from either solar only, or solar plus grid. There seems to be no option to choose grid only. This doesn't seem to worry him, but then he's on Flux and it seems to be suitable for him. However, prodding some buttons on my own app, I found something under "What's New" dated 21st June. Some of it is about changing the text descriptions of what the functions do to reduce confusion. Not sure that has been entirely successful. But then there's this.

"Please note that the "Timed Discharge" mode has been temporarily removed from these inverters settings as it was not functioning as designed when used with older firmware (was not acting in a time window), the functionality will be re-introduced later via an abstraction."

I have no idea what that means. I have a "Timed Discharge" setting, but when I tried it, it didn't seem to do anything. Does that mean it hasn't been removed from my inverter settings because it's not "older firmware"? Or does it mean that it's not functioning? Or not functioning as desired? I still don't know what it's supposed to do. If it's meant to do what I want to do, then they're not being at all clear about it.

Timed Discharge seems to be a new thing since the version of the app on the video, but why did they introduce it as a separate command from Timed Export, and what's it meant to accomplish?

I expect that soon enough your solar will drop off and you won't be so worried about it. The solar will just top up the battery, which will then get you through until the next evening session.

Then when Spring comes around you can focus on export again.

That's totally not the case. The solar is always "costing" me 15p if I use it, as opposed to the contents of the battery - if it was only being filled from the grid - costing me only 7p. Putting the solar into the house or into the battery is basically costing me 8p more per kwh compared to using off-peak power from the battery. That isn't going to change just because it's winter.

It doesn't appear that I need the solar to top up the battery at any point. The battery has a usable capacity of 9 kwh and I expect that to see me through from 5.30 am to 11.30 pm without needing topped up. Particularly considering that I can move washing machine and dishwasher to operate after 11.30 pm.

Because of the way the tariffs are set the most advantageous thing to me is to export ALL the solar and run the house entirely on the battery, which is charged up overnight. The work-round of exporting the entire contents of the battery in the late evening works, but it's proving to be a complete pain in the arse. I'm looking for a setting to tell the inverter not to give solar to the house and not to let the battery take solar to charge, but there isn't one.

 

[Gadget Geek]

That's totally not the case. The solar is always "costing" me 15p if I use it, as opposed to the contents of the battery - if it was only being filled from the grid - costing me only 7p. Putting the solar into the house or into the battery is basically costing me 8p more per kwh compared to using off-peak power from the battery. That isn't going to change just because it's winter.

I think you have summed up the issue perfectly with this statement.

It looks like there is an issue with the Timed Discharge on the app and the firmware of some inverters so the function has been disabled for now. That is definately the function you want, so hopefully it will be sorfted by the time your panels start to produce some serious kW.

 

[Rolfe]

Once again, that's not the point. When the panels are producing serious kw, I get tons of export anyway. The issue is a whole-year-round one, in which all the electricity used by the house is taken from the 15p solar rather than the 7p off-peak mains feed. It's probably worse during the winter, as the house is using more electricity then. Whether the excess solar is minimal or in the tens of kwh, the problem of the house wanting it at 15p rather than using the battery at 7p is exactly the same.

 

[johnb80]

I don't think that would work - though I have been wrong about things before. If the battery is below 100%, and there is more solar than the house needs, then the battery will take that solar. No way to stop it that I can see. Also no way to get the house to use the battery in preference to the solar.

Most inverters that Ive seen and definately on my Growatt theres a 'grid first' and 'battery first' options that can be set with a time schedule, this sounds like what youre youre trying to achieve. What make and model of inverter do you have?

 

[Rolfe]

GivEnergy 5 kw, I think Gen 3.

I watched that entire video about the system, but it's a year old, the relevant part of the app looks completely different now, and the maker of the video doesn't even mention the issue, probably because he's on Intelligent Flux, not Intelligent Go.

I did notice at the top of his screen there was an option for charging the battery. The only two choices were solar only and solar plus grid. No option for grid only.

The system as I have set it up is working more or less OK. There is a window of about 25 minutes for the battery to get to empty, which I seem to be hitting. On Monday though (dull evening, used oven) I was just two minutes into it, which was fine, but two minutes the other way is something I want to avoid. Yesterday, in contrast (brighter evening, didn't use the oven), I was 20 minutes into it. Lost 0.5p as a result (not breaking the bank) but also it meant that I'd have had to wait till ten to midnight before turning on the dishwasher or washing machine. Again not a huge imposition but it's hardly set-and-forget.

Fiscally, it's not causing a loss. Every day so far the battery has exported more than the solar+battery consumption of the house. The problems lie elsewhere.

1. It's a royal pain in the arse. If I'm cooking in the evening I'm thinking, is this going to use so much battery that I need to pause the export to hit the magic window? Conversely, if I'm going to use the dishwasher or washing machine, I have to check that the export has finished before I start.

2. It's a bodge-up, a real one. All day, if I use electricity, I'm thinking, this is costing me 15p/unit, when I was so sure when I got the system that I'd only be paying 7p/unit. I'm getting it back later, but it feels all wrong.

3. It's forcing me to defer dishwasher and washing machine till after the export has finished, whereas if the system worked as it ought to do, and there was enough capacity in the battery to cover it, I could run them at any time. (Yes, maybe this could be covered by the swings and roundabouts of the battery export, but it's all too damn complicated.)

4. I do wonder whether this life is conducive to good battery health long term. It spends 19 hours a day at 100% charge, then 2 hours forced export at maximum speed, followed by 3 hours on charge. If it was working as it should, it would charge for three hours, spend only another three at 100%, then discharge gradually over the next 18 hours. It's LFP, it can probably take it, but still, it doesn't sound optimum.

I have emailed GivEnergy, so we'll see what they say. I mean, how long have these tariffs been available that mandate this way of operating? Surely they should have it covered by now.

 

[Bam Bam]

I watched that entire video about the system, but it's a year old, the relevant part of the app looks completely different now, and the maker of the video doesn't even mention the issue, probably because he's on Intelligent Flux, not Intelligent Go.

2. It's a bodge-up, a real one. All day, if I use electricity, I'm thinking, this is costing me 15p/unit, when I was so sure when I got the system that I'd only be paying 7p/unit. I'm getting it back later, but it feels all wrong.

I have emailed GivEnergy, so we'll see what they say. I mean, how long have these tariffs been available that mandate this way of operating? Surely they should have it covered by now.

Yes, they updated the app several times. Older versions many not even work at all any more.

It seems like the problem is getting the optimal discharge each day, then?

You don't want to over export during the day and end up running the house from the grid in the evening? So you need to make a guess each day of what the solar will be and what the consumption will be. Though consumption during the cheap period or when the battery is fully exporting can be ignored.

On the Givenergy website you can add on a solar predictor card, which gets information about your solar array and the daily weather and creates a prediction. It wasn't very accurate for us because we are East-West and I could only set up one array at the time, but it might be better for you.

I wonder if you are that keen on optimising if it would be worth setting up a home assistant that could write instructions for your inverter every hour. Maybe it could even do so based on

But at least I think you may as well discharge half your battery in the morning. You'd get paid for it and then the battery wouldn't be sitting at 100% (not that it is probably a big issue). Set it to full export again when you are cooking in the evening and the battery will effectively cover that.

 

[Rolfe]

My problem is that the house and the battery can't be prevented from taking the solar generation. Everything else is a bodged work-round.

All these complications should be entirely unnecessary. If I discharged the battery in the morning it would simply recharge from the solar on bright days, and risk leaving me without enough capacity on dull days. The battery is already taking more solar than I want it to, and getting it to take even more seems unlikely to help.

I don't want Home Assistant, I don't want complicated scripts relying on weather forecasts (which have no idea whether I intend to cook a full meal in the evening, or go out to dinner), I don't want any of this fuss. I just want to be able to set the system so that neither the battery nor the house takes any of the solar generation, then forget all about it. People with different systems seem to be able to do it, what exactly is GivEnergy's problem?

John, when I said I was happy to let the car charge on the solar as it was set up (until I got the export tariff), simply setting the battery not to use more than 93% in the morning and cancelling that in the evening, you seemed to think that was way too much intervention. I really didn't mind that though. It's this mad carry-on with the export timing that's doing my head in.

 

[Bam Bam]

I just want to be able to set the system so that neither the battery nor the house takes any of the solar generation, then forget all about it. People with different systems seem to be able to do it, what exactly is GivEnergy's problem?

John, when I said I was happy to let the car charge on the solar as it was set up (until I got the export tariff), simply setting the battery not to use more than 93% in the morning and cancelling that in the evening, you seemed to think that was way too much intervention. I really didn't mind that though. It's this mad carry-on with the export timing that's doing my head in.

I think I just don't get your comment about the house "not taking any solar."

The solar is effectively free now you've got the system. It can either go to the house, battery or grid.

You want it to go to the grid to get the export payment? But the house has a draw, and you don't want that to come from the grid (which isn't even possible, you can't give and take at the same time down the same wire), so it has to come from either the battery or the solar. What difference does it make if the house is getting power from the solar vs. the battery?

I think maybe I'm misunderstanding something.

There used to be a battery pause option on an earlier version of the givenergy app but I couldn't get those buttons to work reliably and they removed it from recent versions.

 

[Gadget Geek]

I think I just don't get your comment about the house "not taking any solar."

The solar is effectively free now you've got the system. It can either go to the house, battery or grid.

You want it to go to the grid to get the export payment? But the house has a draw, and you don't want that to come from the grid (which isn't even possible, you can't give and take at the same time down the same wire), so it has to come from either the battery or the solar. What difference does it make if the house is getting power from the solar vs. the battery?

I think maybe I'm misunderstanding something.

There used to be a battery pause option on an earlier version of the givenergy app but I couldn't get those buttons to work reliably and they removed it from recent versions.

I didn't get it at first, but see Rolfe's previous post:

"That's totally not the case. The solar is always "costing" me 15p if I use it, as opposed to the contents of the battery - if it was only being filled from the grid - costing me only 7p. Putting the solar into the house or into the battery is basically costing me 8p more per kwh compared to using off-peak power from the battery. That isn't going to change just because it's winter."

When the sun shines, she wants the house to run on the battery, which is 7p kWH, and the solar to export at 15p kWh, which means she is making 8p on every kWh.

 

[Rolfe]

I think I just don't get your comment about the house "not taking any solar."

The solar is effectively free now you've got the system. It can either go to the house, battery or grid.

You need to re-think this. The solar isn't "free" now that I have my export tariff. (It was free before then, because if I didn't use it, it had no value to me.) The solar is worth 15p/unit to me, because that is what I can sell it to Octopus for. Every kwh of solar I use is 15p I don't have in my credit account. Why would I want to use electricity at 15p/unit when I have electricity I bought for 7p/unit sitting right there in the battery?

You want it to go to the grid to get the export payment? But the house has a draw, and you don't want that to come from the grid (which isn't even possible, you can't give and take at the same time down the same wire), so it has to come from either the battery or the solar. What difference does it make if the house is getting power from the solar vs. the battery?

The difference it makes is 8p/unit. The electricity in the battery cost 7p/unit. The solar is worth 15p/unit to me. I'm being forced to use electricity at a cost to me of 15p/unit, rather than the electricity I paid 7p/unit for, and have stored ready for use.

I don't want the house to draw from the grid during the day! That would be even worse, that would be 23p/unit. I want the house to draw from the battery during the day. I want it to use that nice 7p/unit electricity in the battery that I put there overnight for it to use. And I want the battery to give the house that electricity, and keep its thieving hands off the solar too, so that these nice people at Octopus will give us 15p for it. As I see it, the purpose of the battery is to take electricity when it's at its lowest price, that is 11.30 pm till 5.30 am, and dispense it when electricity is at a higher price, that is 5.30 am till 11.30 pm. It's not doing that. It's insisting on holding on to the cheap electricity all day, when I want to use it, and to add insult to injury, if it does grudgingly dispense some to the house, it immediately claws it back from the solar as soon as it can.

I think maybe I'm misunderstanding something.

There used to be a battery pause option on an earlier version of the givenergy app but I couldn't get those buttons to work reliably and they removed it from recent versions.

I think you're seeing the solar as "free" when it isn't. If I use something I could have sold for 15p, I've lost 15p. If I use something I could have sold for 15p, rather than using an identical item I bought for 7p, I've lost 8p.

I'm not sure what good pausing the battery would do anyway. I want it to discharge to the house during the day, not sit idle. That bloody app seems to have a bunch of facilities that I can't see any rational use for in the normal course of events, but not to be able to do things that would be extremely useful.

I think I'm just venting now. If it turns out that what I want to do is actually against the laws of physics (although I don't see why it would be) then I'll suck up the work-round with good grace. But as it is, it looks like a badly-designed system to me.

Hopefully I'll get used to the work-round and it will cease to annoy the hell out of me.