Circular reasoning (Rolfe's solar energy system)

[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.

Well, while I still don't entirely understand the how or the why of what is going on, Duward and I arrived at what might be an interim solution and might be a final one, depending on how it goes. It's going fine so far. But if it doesn't work, then the option of changing the wiring is still there.

Duward seems to have got up to speed on the wiring issue, but says he isn't entirely convinced that John's suggested remedy is the best one. Although the question of pre-heating wasn't something he'd thought of (he doesn't have an EV himself), he did point out what I had also noticed, which is that there is a definite advantage to letting the car have access to some of the battery. By smoothing over the peaks and troughs of solar generation, the battery allows more of the generation to go into the car and prevents repeated switching off and on as the weather changes.

So his suggestion was when the car is plugged in and expected to charge from the solar, to change the battery setting in the morning so that the battery isn't allowed to discharge more than a pre-set percent. I'm still trying to figure out what the best percent is to set it at, but the answer I think is somewhere between 90% and 94% (which leaves 91% or 95% in the battery).

This should absolutely prevent the issue John has warned about, what he called "resonance", with the feed to the Zappi ramping up so that the battery is drained very quickly. Once the battery gets to the pre-set limit, the feed will be cut. It will also prevent the issue of the battery continuing to be drained by a relatively low-level charge at the end of the day or if the weather turns very dull for a prolonged period.

It's not too hard to remember to change the protected battery % at the start of the day. What is slightly more difficult to remember is to change it back in the evening. Maybe I'll set an alarm on my phone for the time I expect to have to do that.

Most of the time there is a reasonable window to get this done. The Zappi cuts out while there is still some solar, which then starts to re-charge the battery. Just remember to allow the house access to the battery before switching on the oven or before it gets to the point where the battery has to take over running the house.

Yesterday this worked well. The sunny intervals were quite interval-ish and charging cut out several times while waiting for surplus, and the battery stayed above the 90% set limit. Then in the evening charging cut out while the solar was gradually decreasing. After that happened the remaining generation went both to the Eddi and to recharge the battery, so that by the time the sun went completely the water was hot and the battery back at 100%. Just, y'know, remember to give the house access to the battery before you switch on the oven... (I spotted it immediately, but I need to bear that in mind.) I only got 9.2 kWh into the car but I think it would have been less if it hadn't been for the battery tiding the charge over the shorter breaks in the sunshine.

Today I'd say it worked well too, though slightly differently. Here's the graph.

Again I set the battery limit to 90% some time in the morning. This time the sunny intervals were frequent enough that the car never stopped charging from when it started at 9 am until it was cut out by the battery falling below its limit at 6pm. I got 19 kWh into the car despite the intermittent sun. Three times during the day it was very close to cutting out, but the solar generation picked up just in time. (Around 4 pm the battery bridged a 15-minute rainstorm when it was extremely dull.) Then when it did pick up, the generation was split between the Zappi and the battery so that the battery had some reserves again the next time the solar dipped.

The difference this time was that just as the battery was approaching its cut-off in the evening the skies darkened and it began to rain heavily. That meant that there was practically no generation left to recharge the battery or indeed to run the Eddi after the Zappi had given up. (Indeed the Eddi didn't get much of a look-in in the morning either, as the solar generation shot up just about the time when surplus was due to appear so that the Zappi more or less grabbed the lot.)

So maybe a slightly higher cut-off would be appropriate so that it doesn't all fall off a cliff quite so suddenly in the evening. On the other hand it is very dependent on the weather. I'll have to try it a few more times. The car still isn't full, and I'm out (in the car) in the afternoon, so I'll see what happens tomorrow evening if I set the cut-off at maybe 94%.

It would be nice if it was possible to schedule these changes in battery reserve capacity, but it's no chore to remember to increase the reserve in the morning, and if the car is still charging by evening an alarm on the phone (or a post-it on the oven door) should do it. It does mean that the system can be ignored all day, as it's impossible for it to do anything disastrous. It's not possible (in summer) that the solar generation won't be enough to power the house during daylight hours.

Today there is the issue that the water heating didn't happen, and maybe it would have if I'd set the reserve battery a bit higher and the charging had been cut a couple of times. But if the water isn't hot enough I have other options - either simply use some battery to heat the water through an Eddi boost, or, if it's chilly enough in the evening so I have to turn on the central heating for a couple of hours, let the boiler heat the water at the same time.

So far so good. As far as I am concerned the daytime charging issues are a solved problem.

I don't know about the overnight charging issue yet, because the solar has actually managed to keep pace with my driving - which I didn't actually expect. The solution there is to set the house battery to recharge from the grid while the car is charging, so that the battery doesn't discharge to support the Zappi's demands. I can only assume that's what everyone else with these systems is doing (although Duward hasn't explicitly confirmed it), so I imagine it will work.

If I get that bloody G99 next week then it will all become a lot less complicated, but I'm glad I've learned all this.

 

[Exdro]

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

Sorry for delay in answering. The V2L lead was provided by MG UK as smal compensation for my car being investigated for some time for a faulty noisy wheel bearing. (Diagnosed by AA. Car was off road for three weeks. Came back with no noisy bearing saying that garage could not find anything wrong). Been fine ever since, but they gave me the MG badged V2L cable with double socket. Have used on ZSEV and MG4. Works well.

 

[Rolfe]

So far so good. I've had another couple of days experience with this, and at the moment I've settled on 93% battery protected. I just have to remember to set this in the morning (if the car is charging from the solar) then turn it back to the default 4% once the car is no longer charging. I can then ignore the entire thing, safe in the knowledge that if the solar generation goes right down the home battery will be protected from drain, and there's no chance of this "ramping-up" effect John has described.

I think I prefer it to changing the wiring, because letting the car have some access to the home battery seems very useful on days when clouds are scudding across the sky and the generation is constantly falling below what it needs to charge the car, then picking up again a few minutes later.

It also means that the car will pre-condition from the home battery rather than the mains.

It all depends if youre happy with the work around.

They probably wouldnt do anything against you anyway but worth bearing in mind.

Your choice

If you check back through posts on this subject you will find it was me that suggested you operate in the way your describe, export everything.

OK, good luck with that, you may like to consider what happens if Octopus give you a schedule that starts at 19:30, ends at 23:00, starts again at 04:30 and ends at 09:30, yes it does happen and I have exactly this schedule now on my system.

You certainly will

As opposed to the fact there are thousands of people on social media and forums experiencing this exacft problem and asking for help. Why would that be?



Wow,

Nope, nor should you BUT when the issue is explained and the solution presented which is not 'Non Standard' as you put it, I would have thought it warranted some credibility. To be honest, I'm not worried either way, what you choose. I do feel however that the true picture should be presented on the forum to help others that may be starting out on a similar path, hence why I picked up on references to Zappi problem and Octopus being at fault, neither being the case.

Porting this from a thread where it wasn't really appropriate.

John, that's what I'm trying to establish, whether I'm happy with the work-round. I'm certainly happy with the work-round for the daytime issue, because it allows the battery to give some support to the car charging on days when clouds are scudding across the sky and the solar excess goes up and down like a yoyo, and it completely eliminates the issue you seemed most concerned about when you first raised the topic, the danger of a runaway escalating drain emptying the home battery in no time flat.

I'd like to keep the present wiring because of the advantage on those windy sunshine-and-cloud days, and because it will allow me to pre-condition the car from the home battery rather than fron the grid at peak prices.

You have given me a number of pieces of good advice, and I'm grateful for that, but I also have to take into consideration what my installer is suggesting. I have agreed with him that the option to alter the wiring as you suggest is there if I can't find an acceptable work-round, but I want to look at the alternatives before insisting that he get his pliers out.

While the daytime issue is something that isn't going to be experienced by people who are exporting all the solar they can while living on the cheap-rate tariff, the night-time issue clearly affects those who are doing exactly that - probably most people. Oddly enough though, I don't recall you warning of this issue, only about the possibility of runaway battery drain during the day.

The issue is that when the car charges from the mains, only 4 kW comes from the mains while the other 3 kW is drained from the home battery. Not only that, once the scheduled charge time has come to an end, the drain from the home battery into the car continues at a more variable level, around 2 kW, until the battery is empty. After which time the house has nothing to live on but mains power. Like so. (Incidentally, I'd love to know where the battery got that extra 10% it suddenly found around 5 am. Not from the solar, there was very little solar that early, and not from the mains. There isn't even any indication on the graph of the battery recharging. It's a mystery.)

In this instance, the continuing drain between the scheduled charge periods and then after the second one was an even bigger issue than the 3 kW drain while the car was drawing from the mains. If the house battery had ONLY contributed 3 kW for about 40 minutes (the time it took for Octopus to deliver the scheduled 10% to the car battery) there would have been plenty left. It's a 9.5 kWh battery and it could spare 2 kWh which is what was probably taken during the Octopus scheduled charge. It was the drain following on from the scheduled charge that killed it.

This was a completely unexpected behaviour, to me. I have some idea why it is happening. What I need to know before I get all heavy-handed with Duward and insist he rewire the system he installed is, how are his other customers working round it? This isn't some unusual "resonance" effect that's only going to happen occasionally because of a combination of circumstances, this is clearly SOP for the system. And yet other people are not squealing about it.

If there is some reason I can't live with the work-around other people are using then the rewiring option is still there. But I actually think it's quite unlikely I won't be able to cope with a work-round everyone else is coping with.

And no, not "wow". On the one hand I have someone on the internet saying "do it my way because I told you to and I know best" and on the other hand I have Duward sitting right in front of me saying "I think that solution is a bit old-school, and it should be possible to operate the system without losing the benefits of giving the charger some access to the home battery." I know who sounds more reasonable and I know what I'm going to try first.

 

[GaryMG4]

Coincidentally a recent YouTube video just appeared in my stream by Tomas McGuinness about this very problem. He explained the battery drain issue due to positioning CT clamps with some nice simple animations. Interestingly he mentioned a Zappi setting that was supposed trick the Zappi into not draining the battery but it didn't work (for him) on V4 firmware but he had heard that it worked better with the Zappi V5 firmware.

 

[johnb80]

Coincidentally a recent YouTube video just appeared in my stream by Tomas McGuinness about this very problem. He explained the battery drain issue due to positioning CT clamps with some nice simple animations.

It's the positioning of the CT clamps for the inverter supply thats critical. In the simplest of terms if the inverter sees grid import happening it does exactly what it should, it supplies the energy for the load from PV or battery or both. The problem arises when the feed to the Zappi or any other wallbox comes from that supply, the inverter sees a legitimate load and supplies the power. The solution is feeding the wallbox from a point after the meter but before the CT's for the inverter. Its the only way to guarantee house batteries wont be affected

Interestingly he mentioned a Zappi setting that was supposed trick the Zappi into not draining the battery but it didn't work (for him) on V4 firmware but he had heard that it worked better with the Zappi V5 firmware.

You can minimise the effect by turning up the export threshold before Zappi starts to charge and also setting an export target in the inverter. Both work arounds help but the only real way to stop this happening is by making the inverter not react to Wallbox load and the easy way to do that is the position of the CT clamp.

Heres a video explaining it in practical terms:



Could you give a link to the video you referenced please, I'd be interested to see what they say.

Found it:-


It's exactly what Ive been saying and advising, I suspect the document on the MyEnergi site is my document

 

[GaryMG4]

Could you give a link to the video you referenced please, I'd be interested to see what they say.

Here you go

 

[Rolfe]

Thanks for these videos, I'll try to find time between Wimbledon matches to watch them.

Still haven't heard a dicky-bird about the G99.

Sitting here watching the rain fall. I was a little concerned because the forecast was dreadful and I accidentally left on some strip lights in the garage which doubled the normal house load overnight and left the battery lower than usual in the morning (40%). However, as forecast, it was actually sunny first thing in the morning. The battery was at 100% by ten, and the water tank was hot by 10.30. Even now, although it's pouring, the solar is supporting the house load, occasionally bringing the water tank back to temperature, and coping with me boiling the kettle with a little bit of help from the battery. Battery is back to 100% and I'm actually exporting about 500 watts.

So really, this day is foul, but the solar is more than ample since I don't have to charge the car today. I am back to wondering how bad it actually was on one day when I was in Sussex and the battery never made it to 100% all day, there was never any excess, and even the Eddi didn't get a look in.

I mean, seriously, what was it like? The battery was at 72% when the solar began to take over, but even so the best it got to all day was 94%. There was no demand other than the basic house load because I and the car were 450 miles away. I'm thinking heavy black thunderclouds all day.

I've watched the videos, and they aren't helping my issue. Both the videos John posted are talking about stopping the Zappi from emptying the battery while charging from solar. The second one was particularly informative, giving a complete and detailed description of the "ramping up" issue that John already described. But this is not a problem for me. I am perfectly happy to limit the battery reserve capacity manually while the car is charging from the solar, which stops the issue dead in its tracks. Doing that works really well, because it irons out the issue of the Zappi always waiting for 40 seconds to see if the solar excess is going to continue before it starts charging. In the sort of weather I'm seeing a lot of at the moment that's just a pain.

Nobody is even mentioning the issue that is at present my main concern, which is this.

This has nothing at all to do with the solar excess. This is all happening at dead of night. It has nothing at all to do with the inverter trying to match the solar, or support the Zappi load while the sun is behind a cloud. The minute the command comes to charge the car, the inverter immediately splits the load 4:3 between the grid and the battery.

Then, once charging has stopped (but the EV is not full) the inverter continues to supply the Zappi in the same somewhere-around-2kW pattern as I see when the solar has faded.

I appreciate that this is a different aspect of the same issue (the inverter seeing the Zappi as a legitimate load), and that the same solution would cover it, but it's a different manifestation. I'd be a lot more persuadable if I was hearing people talk about this as being the problem they were grappling with, rather than the daytime problem while charging from solar. If for no other reason than that charging overnight is almost certainly the more common behaviour.

As an aside, with the dull weather we've been having this week, I'm finding that the available solar keeps pace just fine with the house needs. The battery charges from the solar and the Eddi heats from the solar. There might be a little bit of surplus but not much. So the day I find I need to charge the car, I would want to charge from the mains overnight, but still keep the rest of the system running as it does. Do that, and I'm right back in that problem again. And yet nobody is making videos talking about that issue as the reason for rewiring the system? Why not? It's the more serious issue and surely the more common one.

 

[GaryMG4]

I don't have a Zappi, nor do I have a battery but am watching this thread with interest in case I go down this route. You mentioned you have neighbours with the 'same' set up, do they have the same issue (even if they are not aware of it)? If not are they on the same firmware as you? It sounds as though there is some unexpected interaction between the Zappi and inverter that is causing the problem. If it isn't a common problem then maybe some feedback to the manufacturers might help. It does make me think that if I can cope just using Go and the granny I should stick with it.

 

[johnb80]

Nobody is even mentioning the issue that is at present my main concern, which is this.

View attachment 27985

A key for the graph would be helpful.

This has nothing at all to do with the solar excess. This is all happening at dead of night. It has nothing at all to do with the inverter trying to match the solar, or support the Zappi load while the sun is behind a cloud. The minute the command comes to charge the car, the inverter immediately splits the load 4:3 between the grid and the battery.

What min green value do you have set in the Zappi?

I appreciate that this is a different aspect of the same issue (the inverter seeing the Zappi as a legitimate load), and that the same solution would cover it, but it's a different manifestation. I'd be a lot more persuadable if I was hearing people talk about this as being the problem they were grappling with, rather than the daytime problem while charging from solar. If for no other reason than that charging overnight is almost certainly the more common behaviour.

Still symptoms, not getting to the root cause of the problem. What does your 'expert' have to say from his experience having done hundreds of similar install?

As an aside, with the dull weather we've been having this week, I'm finding that the available solar keeps pace just fine with the house needs. The battery charges from the solar and the Eddi heats from the solar. There might be a little bit of surplus but not much. So the day I find I need to charge the car, I would want to charge from the mains overnight, but still keep the rest of the system running as it does. Do that, and I'm right back in that problem again.

Yep

And yet nobody is making videos talking about that issue as the reason for rewiring the system? Why not? It's the more serious issue and surely the more common one.

Why havent you made a video about the problem? From my perspective having helped loads of people out with similar problems with 100% success, I haven't done a video, nor do I intend to. Why would anyone want to do a video? Why take the time and trouble? In all honesty it would probably invoke adverse comments so I don't see the point. I just try to help people directly on forums like this, MyEnergi and Facebook. At the end of the day, you can advise people but if they choose not to follow the advice that's the end of it as far as I'm concerned.

 

[Rolfe]

I haven't spoken to my neighbours about it yet. They're both very busy and I don't like to intrude. I want to see first what happens when I decide to charge overnight and use the solution I think will work. (I also don't make YouTube videos. But lots of people do, usually about problems they have solutions for. Many seem very keen to do it.)

Given that the issue everyone seems most exercised by is the daytime one, why are they rejecting the simple solution of protecting say 95% of the battery when the car is charging from the solar? I did it again today, got over 14 kWh into the battery during the afternoon. The battery kept the charge going when clouds came across the sun, then the charge was cut automatically at 5.45 when the solar faded and the battery dropped to the pre-set level. There was enough low-level sun left after that for the battery to recharge.

 

[johnb80]

And how do you ‘protect’ x% of the battery? How does it do it? How does the system react?

 

[Rolfe]

It's a setting in the GivEnergy app. You can set it to anything between 4% and 100%. The battery will only discharge until it gets to the % you have set it at, then it stops. Duward said, you can choose how much of the battery you want to give to the car, you could even give it 40-50% if you aren't going to use more than say 40% overnight. But I'm settling on protecting about 93-94%. It seems enough to let the charge keep going during intermittent sunshine, but then at the end of the day the battery isn't so low that can't recover to 100% from the remaining evening generation.

It works well in this situation because once the set % has been reached the battery stops supporting the Zappi charge, leading to the car charging being stopped (after a few seconds of draw from the grid). Once the Zappi is idle the battery has exclusive access to whatever solar is being generated, and starts to recharge. If the issue is a prolonged dull spell and the sun comes back out so that enough excess appears to charge the car the Zappi will resume the charge, rinse and repeat. If the issue is dusk, then excess is not going to appear and the Zappi will stay idle. All you have to do is to remember to change the protected battery % back to 4% before the normal evening/night house load takes it back below the set daytime %.

Another little advantage is that when it has been cloudy and the sun then comes out full force the battery is below 100% and I get the benefit of the full solar generation, uncapped by the inverter rating.

I'm completely happy with this solution to the daytime issue. It seems incontrovertible that it will also protect against the ramping-up phenomenon, which seems to be the main problem I'm hearing complained about.

A key for the graph would be helpful.

What min green value do you have set in the Zappi?

View attachment 27986

I thought the graph was reasonably self-evident.

Watts on the left, positive numbers are house draw (green, which includes the Zappi draw), battery discharge (blue, which mostly appears superimposed on the green) generation (yellow) and export (red), but there isn't enough of either of these latter two to show up at this time of night.

Negative numbers are grid import (red) and battery recharging (blue, but there isn't any evident here, even when the battery appears to have acquired 10% charge from somewhere).

The right-hand y-axis which isn't shown is battery %, but it runs from 0% to 100% in 10% increments. the blue line is battery %. It was at 90%, supporting the house overnight load, when the scheduled charge started, and when it hit 5% just after 4 am (the protected % was set at 4%), it stopped discharging and the Zappi stopped charging the car.

As I said, the real killer was that the Zappi continued to draw charge from the battery even when the scheduled charge had stopped. I think the battery only gave about 2 kWh to the car while the scheduled Octopus charge was happening, and that wouldn't have been much of an issue on this occasion. The other ~4 kWh the car got (over and above the grid draw) was due to the continuing charging of the car once the Octopus period had ended.

I've never seen these Zappi menus. Something else to investigate, I suppose.

Here is today's graph, with all the labels. I will go through it chronologically.

Up till 6am the battery is powering the basic house load. It bottoms out at 65% as the solar begins to take over. The battery recharges from the solar between 6 am and 10 am. About 9.45 am, with the battery nearing full, the Eddi starts to heat the water. 10 am to 11.30 is a mix of the Eddi trying to heat the water but being hampered by the dishwasher running - I set the dishwasher going at 10 am when I left the house, in the car. By 11.30 the dishwasher was done and so was the water heating. With nothing else to do with the solar generation, the system started exporting. There was an extra burst of power sent to the Eddi about 12.40.

At 1.30 I returned home and plugged the car in. It started charging immediately. The afternoon was a lot sunnier than the morning, but there were still clouds around. Several times during the afternoon a cloud crossed the sun and excess fell below what the Zappi was taking. Each time the battery sprang into action to bridge the gap - you can see the shadow of the battery discharges behind the green of the Zappi load. Then each time the sun came out again the excess above the 5 kW the inverter is set at was fed to the battery to recharge it for the next cloud. The battery didn't fall below 95% at any point in this process. (There was some kettle-boiling going on here too.)

As the afternoon wore on the solar generation waned and the power going into the Zappi waned with it. Several times a small interruption was bridged by the battery, which then recharged. About 5.30 the solar waned to the point where it couldn't support the Zappi charging any more. The system called on the battery to maintain the Zappi drawing about 2 kW, and the battery % charge declined. At 5.45 it reached 93%, the set reserve capacity, and the battery abruptly stopped feeding the load. I noticed a transient draw from the grid of about the amount the battery had been supplying, but very quickly the system re-balanced itself so that the remaining solar was powering the house load and recharging the battery.

By 6.50 the battery was back at 100%, but then a couple of things happened - the solar dipped, and I started to cook the evening meal. That last green peak is the grill. After that there was still a small amount of solar that ticked the battery back up to 95%, but the solar soon disappeared and the battery gradually took over the house load.

This works a treat. All I have to do is remember, when the car is charging from solar, to flip the reserve % on the battery up to say 93-94%. That will be enough to tide the Zappi over normal clouds going past. If it gets gloomier and the battery hits the reserve %, power to the Zappi will be cut, the remaining solar will be redirected to recharging the battery, and if the sun comes out again so that there's enough excess, it can start again. Then once it's evening and the sun is going down, remember to flip the reserve % back down to 4% so the house has full call on the battery overnight. On this particular day I had till 9 pm to remember to do this, before the battery would have passed the 93% reserve limit powering the house.

If the daytime battery drain was the only issue, from my point of view this solution is preferable to denying the Zappi any power from the battery, so that it keeps cutting out every time a cloud goes over the sun. (It also allows pre-conditioning to take power from the home battery rather than from the grid at peak times, as I said.)

I'm getting so much solar I still haven't had to ask for an overnight charge so I can see what to do about that. Might happen the middle of next week. I'm still a bit puzzled as to why I haven't seen anyone describing what I encountered when I got the overnight charge I wasn't expecting.

 

[decrep]

Here is today's graph, with all the labels. I will go through it chronologically.

View attachment 27999

Thanks for that Rolfe!!
Great explanation of exactly what's going on.
Gives me food for thought, about how I should proceed.
But we don't have the same systems in place here, I'll need to do some research.

The only downside is having to remember to change battery %. That's where I'd fall down

 

[johnb80]

It's a setting in the GivEnergy app. You can set it to anything between 4% and 100%. The battery will only discharge until it gets to the % you have set it at, then it stops. Duward said, you can choose how much of the battery you want to give to the car, you could even give it 40-50% if you aren't going to use more than say 40% overnight. But I'm settling on protecting about 93-94%. It seems enough to let the charge keep going during intermittent sunshine, but then at the end of the day the battery isn't so low that can't recover to 100% from the remaining evening generation.

Surely with this in place it will prevent discharge further but you have strangled your system, if the house demands 6kW eg kettle and oven or washing machine, you will be importing from the grid?

It works well in this situation because once the set % has been reached the battery stops supporting the Zappi charge, leading to the car charging being stopped (after a few seconds of draw from the grid).

I can see it would stop the charge but potentially leave you wide open to grid import for the rest of the house.

Once the Zappi is idle the battery has exclusive access to whatever solar is being generated, and starts to recharge. If the issue is a prolonged dull spell and the sun comes back out so that enough excess appears to charge the car the Zappi will resume the charge, rinse and repeat. If the issue is dusk, then excess is not going to appear and the Zappi will stay idle. All you have to do is to remember to change the protected battery % back to 4% before the normal evening/night house load takes it back below the set daytime %.

I'm amazed you find this an acceptable bodge, but, as long as you're happy that's great.

Another little advantage is that when it has been cloudy and the sun then comes out full force the battery is below 100% and I get the benefit of the full solar generation, uncapped by the inverter rating.

Why was that not the case before?

I seriously doubt this bodge will work successfully through winter, but, good luck to you.

 

[GaryMG4]

I'm guessing that this is only a temporary problem as once you start getting paid for your export you will be better off charging overnight and selling your solar.

 

[Rolfe]

Thanks for that Rolfe!!
Great explanation of exactly what's going on.
Gives me food for thought, about how I should proceed.
But we don't have the same systems in place here, I'll need to do some research.

The only downside is having to remember to change battery %. That's where I'd fall down

It's a fascinating system, with the various components interacting in ways I hadn't really guessed till I started watching it at work. I think Duward was right when he said, over to you now, everyone seems to find a slightly different way of working that suits them. You learn by interacting with the system, not by reading manuals or having someone lecturing at you.

I think the take-home message is, take your time and investigate how it's all working so that you understand the interactions. Work out the capabilities of what you've actually got, and don't go demanding that things be changed just because some bloke on the internet whose qualifications you have no idea about insists that he knows everything. Be sure you really understand what you're asking for and that it's right for your purposes.

I don't find it hard to remember to change the protected battery % in the morning. It's remembering to put it back in the evening that's harder, but that's one reason for setting the protected battery % as high as 93-94%. It means that when the car charging is cut off there's usually still a fair bit of solar around which will recharge the battery and give a reasonable time window before you have to remember to change the % back. Yesterday the car stopped charging at 5.45, but the battery didn't fall back to 93% just from the house load until nine o'clock. I'm thinking maybe a post-it on the oven door, or maybe just taking a guess at the time and setting an alarm on my phone.

I'm guessing that this is only a temporary problem as once you start getting paid for your export you will be better off charging overnight and selling your solar.

Yes. I should have heard about the G99 on Wednesday. Still total radio silence though.

I'm glad I worked it out though, because I understand the system better for the exercise. Also, as I said to Duward, this is for the long term. Right now it's advantageous to sell the solar and live on 7p/unit cheap rate electricity. But it might be in future that the export tariff falls below the overnight import tariff, in which case it would all flip round again and I'll be glad I understand what I'm doing.

Right now though, export ain't happening anyway. The panels are struggling to generate 1 kw, at the time of day when they can do 8 kw in full sun. 700 watts right now, and the battery has just hit 81%. I'm just going to live on the battery today, fortunately there's plenty there to see me through till tomorrow morning when the weather looks to be a lot better.

Now, I'm about to cave in and turn on the central heating. It's completely miserable. I'm not even getting the usual solar gain that usually keeps the conservatory warm in summer even if it's a bit dull.

Surely with this in place it will prevent discharge further but you have strangled your system, if the house demands 6kW eg kettle and oven or washing machine, you will be importing from the grid?

I can see it would stop the charge but potentially leave you wide open to grid import for the rest of the house.

I'm amazed you find this an acceptable bodge, but, as long as you're happy that's great.

Why was that not the case before?

I seriously doubt this bodge will work successfully through winter, but, good luck to you.

Honestly, would you just listen to yourself? It's not a personal insult if I decide not to take your no-doubt-well-meaning advice.

No, the system is not strangled. As I noted, the kettle was on during the period I showed, and you can't even see it. If I turn on an appliance that draws heavily, one of two things happens. Either there is enough solar to support that draw, simply by reducing the power going to the Zappi temporarily (that's what usually happens), or if the battery is already close to 93% and close to cutting the car charging, the extra load causes that to happen, the Zappi stops charging, and all the available solar then goes to the house.

It doesn't leave you wide open to grid import for the rest of the house. The basic starting point is that there is a lot of solar being generated - because the car is charging on the solar. If the house needs a lot of power for some reason then as soon as the battery hits 93% the Zappi stops supplying anything to the car, and the system re-balances so that the house gets the solar instead. Also, if the kettle or the oven or the washing machine come on, it's because I turned them on. If there's any doubt that the solar can support the load, it would take about ten seconds to change the battery setting.

Bodge? Loaded, emotive language, no? It's an extremely simple and effective work-round.

I haven't seen the system operating the way you want it too, but as best I can understand it, as soon as the solar excess dips below what is needed to charge the car, the Zappi will stop charging the car. There is no call on the battery, which therefore remains at 100%. So when the sun comes back out the battery is at 100% and the generation is capped by the inverter. In contrast, the way the system is operating at the moment, the battery is discharged somewhat to support the Zappi charging while the solar excess is low. Then when the sun comes back out generation is uncapped by the inverter and anything above 5 kw goes to recharging the battery. A small gain, but satisfying.

Winter? Who is saying anything about winter? I'm only flipping the protected battery % up when the car is charging from solar excess. I find it highly unlikely that's going to happen at all in winter. Or even today, when it's so dull the panels are struggling to get to 1kw even at noon and the battery itself has only made it to 83%. The car is still plugged in, but frankly it's on to plums. You don't think I'm going to limit the battery discharge when the car isn't charging, when there isn't the remotest possibility of the car charging, do you? This is just something to do on a sunny day when there's enough excess to charge the car directly from the solar. Not many of these in December I don't think.

 

[Bam Bam]

I must say after reading this I'm feeling pretty vindicated going for the Givenergy EVSE to go with my Givenergy battery!

You can set the percentage of solar you want to go into the Car vs. battery and all sorts. Or do battery first and then car. Or just let Octopus control everything, which is what I'll do.

Good job too as the electrician couldn't even fit the EV charger CT clamp in the consumer unit because the main incoming cable was too short/tight. So the EV charger is just piggybacking off the hybrid inverter clamp.

I think we are all people who are keen to tinker with settings and understand systems, but most people just want a system that they can set up and forget.

People who don't want to have a home assistant or manually update their system will be tempted to have either:

• Myenergy system (Libbi + Zappi)
• Givenergy products
• Solar Edge products
• Some other brand that does it all (Duracell?)

Or their installer will have to set things up to get it all communicating together.

I think Givenergy are looking very strong because their products have been more reasonably priced, but I expect prices will even out as the industry matures.

 

[johnb80]

Honestly, would you just listen to yourself? It's not a personal insult if I decide not to take your no-doubt-well-meaning advice.

Absolutely, never took it as an insult.

No, the system is not strangled. As I noted, the kettle was on during the period I showed, and you can't even see it. If I turn on an appliance that draws heavily, one of two things happens. Either there is enough solar to support that draw, simply by reducing the power going to the Zappi temporarily (that's what usually happens), or if the battery is already close to 93% and close to cutting the car charging, the extra load causes that to happen, the Zappi stops charging, and all the available solar then goes to the house.

You misunderstand what I'm saying. If your battery protection has triggered or almost triggered and house loads are switched on when there is insufficient solar to support the load, in this state your system will import from the grid even though you have 90%+ in the battery. Thats what I meant by strangled.

It doesn't leave you wide open to grid import for the rest of the house. The basic starting point is that there is a lot of solar being generated - because the car is charging on the solar. If the house needs a lot of power for some reason then as soon as the battery hits 93% the Zappi stops supplying anything to the car, and the system re-balances so that the house gets the solar instead. Also, if the kettle or the oven or the washing machine come on, it's because I turned them on. If there's any doubt that the solar can support the load, it would take about ten seconds to change the battery setting.

Fine, no problem, right at the start of all of this you said you wanted a system that looked after itself with little intervention, now your saying youre happy with daily intervention.

Bodge? Loaded, emotive language, no? It's an extremely simple and effective work-round.

Nah, it's a bodge

I haven't seen the system operating the way you want it too, but as best I can understand it, as soon as the solar excess dips below what is needed to charge the car, the Zappi will stop charging the car. There is no call on the battery, which therefore remains at 100%. So when the sun comes back out the battery is at 100% and the generation is capped by the inverter. In contrast, the way the system is operating at the moment, the battery is discharged somewhat to support the Zappi charging while the solar excess is low. Then when the sun comes back out generation is uncapped by the inverter and anything above 5 kw goes to recharging the battery. A small gain, but satisfying.

All what I've said allows the Zappi to work as designed without third party batteries and inverters getting involved. It in no way affects the battery and inverter system that you have and allows them to run at full capacity as needed.

Winter? Who is saying anything about winter? I'm only flipping the protected battery % up when the car is charging from solar excess. I find it highly unlikely that's going to happen at all in winter. Or even today, when it's so dull the panels are struggling to get to 1kw even at noon and the battery itself has only made it to 83%. The car is still plugged in, but frankly it's on to plums. You don't think I'm going to limit the battery discharge when the car isn't charging, when there isn't the remotest possibility of the car charging, do you?

Ive no idea what you have planned or how your logic works. I only speak from experience.

At the risk of sounding like a broken record, I will refrain from further comments.

 

[johnb80]

I must say after reading this I'm feeling pretty vindicated going for the Givenergy EVSE to go with my Givenergy battery!

It makes it very tidy when systems can talk to each other. The only downside at the moment is with IOG integration.

You can set the percentage of solar you want to go into the Car vs. battery and all sorts. Or do battery first and then car. Or just let Octopus control everything, which is what I'll do.

Spot on, it's certainly the way things are heading in the future.

Good job too as the electrician couldn't even fit the EV charger CT clamp in the consumer unit because the main incoming cable was too short/tight. So the EV charger is just piggybacking off the hybrid inverter clamp.

That doesnt sound so good, tails shouldnt really be that tight.

I think we are all people who are keen to tinker with settings and understand systems, but most people just want a system that they can set up and forget.

Absolutely

People who don't want to have a home assistant or manually update their system will be tempted to have either:

• Myenergy system (Libbi + Zappi)
• Givenergy products
• Solar Edge products
• Some other brand that does it all (Duracell?)

Or their installer will have to set things up to get it all communicating together.

Exactly, the problem being that wallboxes such as Zappi or Ohme have no published protocols to talk to inverters such as Growatt, Victron etc. If a standard was created like ODBII on car diagnostics, great things could be achieved through communication.

I think Givenergy are looking very strong because their products have been more reasonably priced, but I expect prices will even out as the industry matures.

Givenergy are pretty decent in terms of equipment and prices, there are a few shortcomings but ones easily addressed.

I think the take-home message is, take your time and investigate how it's all working so that you understand the interactions. Work out the capabilities of what you've actually got, and don't go demanding that things be changed just because some bloke on the internet whose qualifications you have no idea about insists that he knows everything. Be sure you really understand what you're asking for and that it's right for your purposes.

Well thanks for that Rolfe, I dont insist I know everything merely told you about this issue, tried to help you pre install. You then experienced the problem and still suggest I'm wrong.
I really dont care any more if your system works or not and I take onboard the personal remarks above - Thank You Very Much.

 

[Bam Bam]

That doesnt sound so good, tails shouldnt really be that tight.

He added RCBOs which are larger than the RCBs they replaced, which required slight rerouting, making it even tighter than it would have been before.

I heard the electrician cursing a lot as he installed everything.

He was the only one who quoted to keep the existing consumer unit. Ended up regretting it I think.