Circular reasoning (Rolfe's solar energy system)

[johnb80]

Thinking of going for a Pod Point 3s. Which distributes solar charging and is also V2G ready.

Nothing I can see on the PodPoint website mentions the 3s and V2G. It is far from a simple thing to manufacture, you have to make a grid tied inverter built into the wallbox in order to use the DC from the car. Me personally, I wouldn't entertain a wallbox that didn't have a display and buttons for control, it relies on connection to Podpoint which is about where you are now with EDF/EO!

 

[Exdro]

Nothing I can see on the PodPoint website mentions the 3s and V2G. It is far from a simple thing to manufacture, you have to make a grid tied inverter built into the wallbox in order to use the DC from the car. Me personally, I wouldn't entertain a wallbox that didn't have a display and buttons for control, it relies on connection to Podpoint which is about where you are now with EDF/EO!

Tx for info. Food for thought. I’ll have a look at Zappi. Not doing anything at present til Ombudsman completes case and makes recommendations.

 

[johnb80]

Tx for info. Food for thought. I’ll have a look at Zappi. Not doing anything at present til Ombudsman completes case and makes recommendations.

Sounds like a plan. Don't be dazzled by V2G ready, thats hogwash IMHO, it will need a lot more than just a wallbox.
In my experience the Ombudsman can take months to make a ruling and in my case (against Together Energy) they agreed but didn't comply. I had to go to court to get my money, it was a mere formality having gained the Ombudsman's decision in my favour.

 

[Exdro]

Sounds like a plan. Don't be dazzled by V2G ready, thats hogwash IMHO, it will need a lot more than just a wallbox.
In my experience the Ombudsman can take months to make a ruling and in my case (against Together Energy) they agreed but didn't comply. I had to go to court to get my money, it was a mere formality having gained the Ombudsman's decision in my favour.

Sorry, not looking for V2G. Considering V2H. But as yet this is not supported. I’ll do a lot more research before making any commitment. By all accounts Octopus seems to be the go to company. Tx for your input.

 

[johnb80]

Sorry, not looking for V2G. Considering V2H. But as yet this is not supported. I’ll do a lot more research before making any commitment. By all accounts Octopus seems to be the go to company. Tx for your input.

V2H is easier but not without it's complications. You have to consider how you connect the 400v DC to your 240v AC to make best use of it. You can of course get the V2L adapters and then plug in items you want to run from the car, not ideal but every little helps as they say. I have addressed this issue by using a 3kW V2L lead and installing a battery charger on my LifeP04 cells in my house battery. The Charger takes the mains from the car and charges my batteries at 3 kW. Completely independent of the house grid supply. The inverter takes the 50v from the battery and is grid tied so it can supply the house as normal. It was the easiest and cheapest way to get V2H working in a very simple way.

 

[Rolfe]

I dont know if I should be worried by you taking aim at me

The windup of charging current can and does occur under certain conditions. It does depend on how your inverter responds and your available energy sources i.e. battery and solar PV.

I remember a mod on here saying that all they wanted was a solar PV / battery system that worked, they wouldn't be monitoring it like we all do etc etc

No it did not, this is NOT a Zappi issue. Your inverter started to draw current from the battery to support the loads you have including Zappi.

Again, not the Zappi, your inverter carried on supplying the energy from the battery. Zappi doesn't know any different, it still sees it is drawing 2kW from the mains and no grid import is happening and therefore continues.

There is no reason for it to stop, until Zappi sees import from the grid, it wont change and thats exactly the problem. If you switched on some heavy loads briefly, more than your inverter can supply eg fan heater, oven, tumble drier etc, Zappi would see grid import happening and after a set delay reduce or stop the charge.

Exactly, you need the feed to the Zappi wiring correctly.

You need to ask the correct question, "why would my inverter behave differently in the afternoon".............
It can be a number of factors that contribute to this effect, the inverter and it's settings are the major influencer. I have two inverters on my system of different makes and until I wired my Zappi correctly one or the other would feed it from the batteries dependent on parameters I had set.

I find its best to set ZAPPI as priority because it needs above 1.4 kW of export to start car charging (thats the minimum charge level on most EV's). So the system monitors the grid export, when it starts to happen, even low levels such as 200 W, Zappi cant use it so second priority Eddi can. Eddi sets the output into the immersion to 200 W, as solar PV increases so does Eddi into the immersion. Once 1.4 kW of excess energy is reached for a short time, Eddi will stop feeding the immersion and Zappi will start the car charging at 1.4 kW. If solar PV drops, Eddi is reinstated and the car charging stopped.

The key issue here is where Zappi is taking the load from, it needs to be BEFORE the solar PV/Battery sensing so that your inverter doesn't see the Zappi load. You also need as a matter of urgency your export tariff sorting and then the system setup becomes very straight forward. Export all what you generate, charge the batteries from the grid 23:30 to 05:30, charge the car overnight and/or during peak times if Octopus give a schedule (it gets you more hours on 7p).

As I've probably mentioned, it's not Zappi doing it, it's your inverter

Well it's all in there above and I did warn you BEFORE you had the install done what was needed. I know living down here in carrot crunching land you might think we know nowt but we do know the odd thing or two from experience and research.

A temporary fix would be to set your house batteries to charge overnight at the same time.

It's inverter behaviour doing exactly what it's supposed to do. It's a bit like have the heating on (that's the inverter) and then opening the windows because it's too warm (that's the load), the temperature inside drops so the boiler ramps up a bit more, the room temperature it too high again so the windows are opened more and so on. This is EXACTLY what's happening with your system.

Understandably, it took me a while with some quite elaborate monitoring going on to troubleshoot the whole system and it is a whole system issue rather than Zappi. I have seen it 100's times on forums and social media and amongst friends and colleagues. Every time, wiring it correctly resolves the issue because the where the Zappi is supplied from is the root cause of it all.

Sorry if I'm not describing this properly, I'm trying to learn. I did try to make your point to my installer before he started wiring the Zappi but he didn't really respond to me and I didn't know enough to press the point. He's willing to address it though, so we take it step by step. (There is also another small problem he's going to fix.) As yet I have never seen the wind-up happen, so I have to address the issues I am seeing.

I could imagine that the tendency to carry on charging the car from the battery at about 2 kW after the solar has faded might be something other clients of his might not have been bothered by, because turning anything on in the kitchen about tea-time is going to stop it, and most people with a car on charge are going to be in the house and at least up for making a cup of tea. (Thinking about it, leaving the Eddi at priority is probably not going to stop it, because the Eddi isn't going to come on if there is no excess. And there is no excess.) Also, people who have their G99s may not even be charging directly from the solar.

What I do find difficult to believe is that nobody else is squealing about the drain on the battery when the car is set to charge overnight. It doesn't hugely matter if the following day is sunny, but it could be a complete pain if the next day is generating very little solar. As you say, setting the battery to charge overnight might be the thing to do, but I want this fixed. Sure, I'll change my habits when the G99 comes through but that's still going to be another two or three weeks. Presuming they don't/can't say I can't have it.

Yes, my aim is not to be monitoring it all the time, but first I have to learn how it works, so that a quick glance occasionally will let me know the score. If I wasn't getting this nutty behaviour with the battery drain I'd already be at that stage I think, but as it is I'm monitoring it to try to understand what the hell it's playing at.

So no, I don't understand why the Zappi (OK, under the guidance of the inverter) would stop the charge when the sun went in in the early afternoon, then start it again once excess solar was available, but under the exact same circumstances in the late afternoon would NOT stop the charge when the sun went in but continue to drain the battery ad infinitum. It didn't seem to need any grid import at the earlier time to trigger the stop, absence of excess solar was enough to do it. Why would absence of excess solar not do the same thing later? The damn thing is on eco+.

I also have zero idea why anyone would put up with a system where the charger automatically takes 3 kW from the battery when asked to charge overnight. Absolutely none of Duward's other customers have squealed about this? Really?

However, assuming that the fix for this is as you describe, I do have a couple of reservations. I notice the battery being called into play to smooth out temporary variations in the solar generation. This seems to work very well, and actually lets more of the solar be used when the battery is charging back up, as for example yesterday, when the generation was only capped when the battery was at 100% and I was seeing up to 7.8 kW solar generation when it wasn't.

This actually worked very well, and I could see the Zappi and the Eddi handing things back and forward, and two or three times the charge stopped to wait for excess, then started again. I worry slightly if this might not work so well and so seamlessly with the different wiring configuration.

The other thing that concerns me is pre-heating the car, which I often do in winter. I've just had the software update that will allow the car to pre-heat while plugged in, taking the electricity from the mains. Obviously I am not pre-heating the car between 11.30 and 5.30, this happens when peak rates are in operation. So does this mean that the car will always be pre-heating using peak electricity prices? I could certainly spare a few kwh from the house battery for that purpose.

I'm trying to learn as much as I can about this before Duward comes back to me later this week. I have sent him your pdfs, but I don't think it's an issue he's dealt with before. I want to be sure there isn't anything I might regret if I lean on him to change it.

PS. I take your point that these problems will go away, or at least be minimised, when I switch to exporting everything I can and living on cheap rate grid electricity stored in the battery. However, who knows what might happen in future. If the export tariff were to fall below the overnight tariff, for example, then I'd want to go back to doing what I'm doing now. And if it's not fixed now, all these problems will re-emerge.

 

[johnb80]

Sorry if I'm not describing this properly, I'm trying to learn. I did try to make your point to my installer before he started wiring the Zappi but he didn't really respond to me and I didn't know enough to press the point. He's willing to address it though, so we take it step by step. (There is also another small problem he's going to fix.) As yet I have never seen the wind-up happen, so I have to address the issues I am seeing.

Windup will only occur under certain circumstances and events but it does happen with the symptoms youre now witnessing. It's a bit like a bridge and resonance happening under certain conditions.

I could imagine that the tendency to carry on charging the car from the battery at about 2 kw after the solar has faded might be something other clients of his might not have been bothered by, because turning anything on in the kitchen about tea-time is going to stop it, and most people with a car on charge are going to be in the house and at least up for making a cup of tea. (Thinking about it, leaving the Eddi at priority is probably not going to stop it, because the Eddi isn't going to come on if there is no excess. And there is no excess.) Also, people who have their G99s may not even be charging directly from the solar.

Agreed

What I do find difficult to believe is that nobody else is squealing about the drain on the battery when the car is set to charge overnight. It doesn't hugely matter if the following day is sunny, but it could be a complete pain if the next day is generating very little solar.

Perhaps most people are charging their batteries off peak too?

As you say, setting the battery to charge overnight might be the thing to do, but I want this fixed. Sure, I'll change my habits when the G99 comes through but that's still going to be another two or three weeks. Presuming they don't/can't say I can't have it.

They have to allow you 3.6 kW so worst case is you limit your export to that.

Yes, my aim is not to be monitoring it all the time, but first I have to learn how it works, so that a quick glance occasionally will let me know the score. If I wasn't getting this nutty behaviour with the battery drain I'd already be at that stage I think, but as it is I'm monitoring it to try to understand what the hell it's playing at.

I know, just a little banter

So no, I don't understand why the Zappi (OK, under the guidance of the inverter) would stop the charge when the sun went in in the early afternoon, then start it again once excess solar was available, but under the exact same circumstances in the late afternoon would NOT stop the charge when the sun went in but continue to drain the battery ad infinitum.

All that Zappi 'knows' is the amount of energy flowing out to the grid, based on that information it tells your EV how much energy it can take from the supply. As your export goes up, it tells the car it can take more and vice versa. The inverter is providing the exported energy from solar PV and when the solar input reduces your inverter starts to take energy from the battery which is exactly what you want it to do supplying your house. Unfortunately, your Zappi is connected to the house load so your system sees it as a legitimate load and will continue to support it from battery. Zappi doesnt know (or care) where the energy comes from, only that energy is available. Only a change in the grid supply will make Zappi adjust the output. Dependent on how good your inverter is at handling shock load eg kettle switching on, washing machine etc, anything that can give a stepped load change which the inverter may not fully support would cause Zappi to see some import and adjust it's output accordingly.

It didn't seem to need any grid import at the earlier time to trigger the stop, absence of excess solar was enough to do it. Why would absence of excess solar not do the same thing later? The damn thing is on eco+.

It is possible that it was a very short term spike, freezer compressor starting or even a neighbouring property either increasing it's export or switching a load off, either will raise the grid voltage and cause a small import into your system.

I also have zero idea why anyone would put up with a system where the charger automatically takes 3 kw from the battery when asked to charge overnight. Absolutely none of Duward's other customers have squealed about this? Really?

Okay, accept it as it is, I have no beef either way, I only speak from experience, I find it equally amazing your installer knew nothing about this issue which is widely discussed online.

However, assuming that the fix for this is as you describe, I do have a couple of reservations. I notice the battery being called into play to smooth out temporary variations in the solar generation. This seems to work very well, and actually lets more of the solar be used when the battery is charging back up, as for example yesterday, when the generation was only capped when the battery was at 100% and I was seeing up to 7.8 kw solar generation when it wasn't.

View attachment 27710

This actually worked very well, and I could see the Zappi and the Eddi handing things back and forward, and two or three times the charge stopped to wait for excess, then started again. I worry slightly if this might not work so well and so seamlessly with the different wiring configuration.

You dont need to worry. Zappi will still see export happening and ramp it's output up, when export reduces it will reduce it's output in the same way, ditto with Eddi, it all stays the same. The only difference is your inverter cant see the Zappi taking the load and therefore wont supply the load from the battery.

The other thing that concerns me is pre-heating the car, which I often do in winter. I've just had the software update that will allow the car to pre-heat while plugged in, taking the electricity from the mains. Obviously I am not pre-heating the car between 11.30 and 5.30, this happens when peak rates are in operation. So does this mean that the car will always be pre-heating using peak electricity prices? I could certainly spare a few kwh from the house battery for that purpose.

It wouldn't be able to take power from your house battery for that. That said, you can only run pre heating for 10 minutes and at approx 3kW thats only 500w taken from your EV battery which is circa 2 miles of your range.

I'm trying to learn as much as I can about this before Duward comes back to me later this week. I have sent him your pdfs, but I don't think it's an issue he's dealt with before. I want to be sure there isn't anything I might regret if I lean on him to change it.

You'll have to make your mind up on this one. I did tell you what would happen before your install, what I predicted IS happening and the solution that I know works along with detailed explanation of why it happens and why the solution stops it happening. Up to you!

PS. I take your point that these problems will go away, or at least be minimised, when I switch to exporting everything I can and living on cheap rate grid electricity stored in the battery. However, who knows what might happen in future. If the export tariff were to fall below the overnight tariff, for example, then I'd want to go back to doing what I'm doing now. And if it's not fixed now, all these problems will re-emerge.

Yep!

Good luck.

 

[Rolfe]

I'm trying my best to follow you, really! I thought my installer might have known about the issue, but it seems he doesn't. He's a sole trader and pretty busy - I doubt if he is online much. He was talking about needing some time off, so he might turn down or postpone a couple of future orders. I know you warned me about the issue in advance, and I did try to raise it with him, but in retrospect neither of us really knew what I was talking about.

I have sent him the pdfs you sent me, but I'm not yet in a position to throw a tantrum and insist that he does what they say. He's coming tomorrow to look at the situation (and fix a problem with the TP link) so I'll see which way the wind is blowing. I can work up to having a row and insisting that he does it your way, but I'd rather he came round on his own without the row, so softly softly. I might, if he seems amenable, try to persuade him to do my system your way as an experiment, and see what happens.

It surprises me greatly that he hasn't had any other customer complaining about the battery drain when the car charges overnight. I suppose it's possible that nobody else on his books has been in a position of wanting to use up solar and so not fill the battery overnight, but I find that quite hard to believe.

The behaviour of the car charging is very consistent. During the morning and up to mid afternoon it stops when the solar generation falls back and starts again when the sun comes out again. Then after about 4.30 pm if/when the solar fades, charging continues at a variable rate of around 2 kw (usually) by taking power from the battery. I've seen it again and again, so it's hard to see how it's something just randomly coming on. Hopefully it might become clearer later on.

Thanks for your patience, you've been a great help in clarifying what questions I need to ask.

 

[johnb80]

I'm trying my best to follow you, really! I thought my installer might have known about the issue, but it seems he doesn't. He's a sole trader and pretty busy - I doubt if he is online much. He was talking about needing some time off, so he might turn down or postpone a couple of future orders. I know you warned me about the issue in advance, and I did try to raise it with him, but in retrospect neither of us really knew what I was talking about.

It's quite amazing that many installers dont fully understand the systems theyre installing. It really is having an understanding of a bigger picture than just the solar or the Zappi.

I have sent him the pdfs you sent me, but I'm not yet in a position to throw a tantrum and insist that he does what they say. He's coming tomorrow to look at the situation (and fix a problem with the TP link) so I'll see which way the wind is blowing. I can work up to having a row and insisting that he does it your way, but I'd rather he came round on his own without the row, so softly softly. I might, if he seems amenable, try to persuade him to do my system your way as an experiment, and see what happens.

Totally agree

It surprises me greatly that he hasn't had any other customer complaining about the battery drain when the car charges overnight. I suppose it's possible that nobody else on his books has been in a position of wanting to use up solar and so not fill the battery overnight, but I find that quite hard to believe.

I suppose the customer base that have EV and Solar is relatively small and of those ones that look at their system and can understand the data even fewer. It will become a bigger problem as more and more people go the EV route.

The behaviour of the car charging is very consistent. During the morning and up to mid afternoon it stops when the solar generation falls back and starts again when the sun comes out again. Then after about 4.30 pm if/when the solar fades, charging continues at a variable rate of around 2 kw (usually) by taking power from the battery. I've seen it again and again, so it's hard to see how it's something just randomly coming on. Hopefully it might become clearer later on.

Thats good if it's repeatable, you need to get your engineer to witness it and let him come up with the solution.

Thanks for your patience, you've been a great help in clarifying what questions I need to ask.

Patience..........? Me............? No, I dont have any (well thats what my better half says anyway).

 

[Rolfe]

Well, today is a different day. The car is charging, but at less than the granny charger would pull, most of the time. It's 100% overcast with intermittent rain. It will be interesting to see what happens.

 

[johnb80]

Well, today is a different day. The car is charging, but at less than the granny charger would pull, most of the time. It's 100% overcast with intermittent rain. It will be interesting to see what happens.

It will depend on the total generation minus the load from the house and batteries), If the excess stays above 1.4 kW all will be good.

 

[Rolfe]

So far so good. It has brightened up a bit.

As regards pre-heating, I waited a year to get the software update so that the car would pre-heat while plugged in but not charging. Having to go out into the snow to unplug the car in order to pre-heat it was a bit counter-productive. Same still applies. I don't want to have to go out in the snow to unplug it to make it take the power from its battery. Also, one pre-heating cycle drops the SoC to 98%, and that's just the cabin. I might want to pre-heat the battery too. This is significant in winter when you have the 51 kWh car.

However, a few kWh from the grid at peak prices isn't exactly a deal-breaker. I don't do it every day.

 

[Rolfe]

OK, not so good now. It has got duller, the excess has dropped way down, the panels are only generating 900 W and the battery is being drained - just as happened when the sun went away in the evening before. Going to stop the rot while I'm ahead, let the battery charge and maybe heat some water while the excess isn't up to charging the car.

I flipped the Eddi back to priority, so the system moved to charging the Eddi rather than the car, but the battery is still being drained. Now it is the Eddi that is sucking the battery dry, as the rain comes on. Now, that was unexpected. I'll give it a few minutes to see what happens.

OK, that's all right. Within a few minutes the battery export reduced itself and the Eddi started taking just the excess. Then the whole thing re-prioritised, and the excess is now going to recharge the battery with both the Eddi and the Zappi waiting for excess.

 

[johnb80]

So far so good. It has brightened up a bit.

As regards pre-heating, I waited a year to get the software update so that the car would pre-heat while plugged in but not charging. Having to go out into the snow to unplug the car in order to pre-heat it was a bit counter-productive. Same still applies. I don't want to have to go out in the snow to unplug it to make it take the power from its battery.

And you dont have to. In the MyEnergo APP set Zappi to stop and it wont provide power to car. Simples!!

Also, one pre-heating cycle drops the SoC to 98%, and that's just the cabin. I might want to pre-heat the battery too. This is significant in winter when you have the 51 kwh car.

Hey, youre talking to someone who's regular steed is only 30 kWh battery!!

However, a few kwh from the grid at peak prices isn't exactly a deal-breaker. I don't do it every day.

You have choice!

 

[johnb80]

OK, not so good now. It has got duller, the excess has dropped way down, the panels are only generating 900 kw

Thats some array you have

and the battery is being drained - just as happened when the sun went away in the evening before. Going to stop the rot while I'm ahead, let the battery charge and maybe heat some water while the excess isn't up to charging the car.

If you leave Zappi as priority over the car, it will take all of the excess until it hits 1.4 kW when it will start charging the car.

I flipped the Eddi back to priority, so the system moved to charging the Eddi rather than the car, but the battery is still being drained. Now it is the Eddi that is sucking the battery dry, as the rain comes on. Now, that was unexpected. I'll give it a few minutes to see what happens.

Eddi is usually quite good with this due to its instant response to energy levels.

OK, that's all right. Within a few minutes the battery export reduced itself and the Eddi started taking just the excess. Then the whole thing re-prioritised, and the excess is now going to recharge the battery with both the Eddi and the Zappi waiting for excess.

Good stuff.

 

[Rolfe]

What is now puzzling me is why the inverter is happy to shove power from the battery to the Zappi ad infinitum if the solar has faded, but in the exact same situation it cuts the power to the Eddi, first so that it's only using what surplus is actually available, and then completely to let the battery recharge.

Leaving the Zappi as priority on a day like today is risky, because the clouds are liable to keep coming over and the battery gets lower and lower. On the other hand, leaving the Eddi as priority means solar is being used to heat and re-heat the water tank which isn't really needed at the moment.

Anyway, Duward should be here in ten minutes.

 

[GaryMG4]

Well, today is a different day. The car is charging, but at less than the granny charger would pull, most of the time. It's 100% overcast with intermittent rain. It will be interesting to see what happens.

It will be interesting to see how your winter generation compares. Last month our SW facing panels generated 1.8x the amount for the whole 1st Nov - 1st Feb quarter last year. I wonder with your higher latitude, if the longer summer days/shorter winter days would make the difference more extreme?

 

[Rolfe]

I would imagine so. I'm seeing the panels start generating at a low level as early as 3.30am at the moment, as I have a clear east aspect. We have pretty short days in winter though. A friend of mine in Glasgow who is on a FiT tariff said she's had calls from her supplier a couple of times asking if her system was out of order because no generation at all had been recorded for several days.

 

[Barrie]

V2H is easier but not without it's complications. You have to consider how you connect the 400v DC to your 240v AC to make best use of it. You can of course get the V2L adapters and then plug in items you want to run from the car, not ideal but every little helps as they say. I have addressed this issue by using a 3kW V2L lead and installing a battery charger on my LifeP04 cells in my house battery. The Charger takes the mains from the car and charges my batteries at 3 kW. Completely independent of the house grid supply. The inverter takes the 50v from the battery and is grid tied so it can supply the house as normal. It was the easiest and cheapest way to get V2H working in a very simple way.

Hi John. Can I ask where you got your 3kw V2L lead ?

 

[johnb80]

Hi John. Can I ask where you got your 3kw V2L lead ?

I don’t remember, I followed a link from a thread on here, I think they were running it on a ZS.