Circular reasoning (Rolfe's solar energy system)

[johnb80]

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.

RCBO's are a good move, stops nuisance tripping taking the whole house out and improves safety for sure.

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

A lot of 'Oh No's or Oh Dear Me' LOL

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

Life can be a cruel teacher at times, sounds like you chose well both in terms of sparky and equipment.

 

[Rolfe]

Absolutely, never took it as an insult.

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.

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.

Nah, it's a bodge

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.

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.

You are still misunderstanding. The 93% protected battery setting is only going to be in place when there is sufficient solar to support the car charging. If something happens in the house that causes the 93% limit to be breached while the car is charging, then the car simply stops charging. (And bear in mind that the something that has happened in the house will be happening because I made it happen. The house is not going to sleepwalk into this situation of its own accord.) At the point this happens, the available solar is simply ressigned to the house load, which is going to be peanuts compared to what the car was getting. I have seen this happen, when I turned on the microwave late in the afternoon when the solar was fading. There was no issue. The Zappi cut out, and the remaining solar easily handled the microwave. And the kettle. And recharged the battery.

I want a system that will look after itself with little intervention. This small work-round is well within the bounds of "little intervention". It is very far from "daily". It's just a small thing to do, takes seconds, on a day where I intend to charge the car directly from the solar input. And once I have the G99 I'm not going to be doing it much, if at all. I now know what to do in the event that I DO want to charge from the solar, to make sure the car doesn't empty the house battery, that's all, without taking the more extreme step of physically rewiring the system - which has its own disadvantages.

I'm still at the stage of learning how the system works, which is the path to being able to leave it to look after itself. So far so good. The thing I am really resisting (despite some cajoling from Duward) is Octopus Flux. That sounds like a freaking career choice. Blowing up the minimal chore of flipping a setting on my phone twice in a day, IF the car is charging from the solar, to "daily intervention" is ludicrous. It takes longer to plug the car in than it does to change the setting.

Frankly, you sound miffed that there's a simple work-round that completely obliterates the danger of the car emptying the battery while charging direct from solar. You're very invested in this rewiring thing, even when it turns out not to be necessary.

You want the Zappi to work without any interaction with the battery or the inverter. That's one way to play it. But when you let the Zappi interact then there are upsides as well as downsides. One is that it takes the battery % down in the middle of the day when there is abundant but intermittent solar, allowing the system to generate its full potential without being capped by the rating of the inverter. The battery tides the Zappi over when a cloud obscures the sun, then recharges from the extra regeneration that wouldn't be there if the battery had been at 100%. It works well. All that's needed is that little insurance policy of setting the protected battery % in the morning, and resetting it in the evening. With that, your concern about the house battery being emptied into the car battery (for whatever reason), has been entirely addressed.

If you don't understand the logic of my argument, then I question whether you really understand anything about this. The work-round is something that is only going to be done on days when there is ample solar to allow the car to charge. Summer or winter. I question whether there will be many, if any such days in winter, but if there were such a day, it would work in just the same way as in the summer, albeit for a much shorter period. But mainly, due to the very low angle of the winter sun and the very short hours of daylight, it isn't something that's at all likely to arise in winter. So why even question "whether this would work successfully through winter"? It's not even relevant.

Continue to comment, or not, as you wish. I've given up trying to mollify you. It seems as if the only response that won't be met with a hostile reaction from you is the news that I have insisted to Duward that he come back and rewire the system the way you want it. That still might happen, I'm still learning, but it's looking less and less likely the more I learn about how to operate the system.

 

[Rolfe]

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.

I am sorry you have chosen to take such a hostile attitude to my attempts to understand how the system interacts, rather than blindly insisting to my installer that he do what you say, no arguing. I'm not done with the learning process yet, not by a long chalk, and I especially have to figure out how to handle overnight charging. But I am now pretty clear in my own mind that your solution is entirely unneccesary to guard against the house battery being excessively drained during the day/evening.

 

[johnb80]

I am sorry you have chosen to take such a hostile attitude to my attempts to understand how the system interacts, rather than blindly insisting to my installer that he do what you say, no arguing. I'm not done with the learning process yet, not by a long chalk, and I especially have to figure out how to handle overnight charging. But I am now pretty clear in my own mind that your solution is entirely unneccesary to guard against the house battery being excessively drained during the day/evening.

No comment.

 

[Rolfe]

Very different day today, with minimal blue sky showing and a very dull period during the middle of the day which momentarily saw the solar only equal the house load.

Around nine I noticed that the generation was high enough that the car (which was still plugged in and at 81%) might start to charge so I spent a horrifically onerous 15 seconds flipping the protected battery level to 94% (I thought I'd try that and see how it went, as opposed to 93% the other day).

The Eddi had a shot at heating just after that, as there was a sudden burst of solar, but soon gave that idea up. However by 10.15 with the battery up to 96% everything started to happen. The Eddi got another brief look-in, but then all the excess was transferred to the Zappi. Didn't last long, because the solar fell away, and the charge was stopped after the battery hit 95%. The battery re-charged a bit, then another spike of solar set the Zappi off again. Again that was short-lived, with the charge stopping on 94% as arranged. Same thing happened a third time. Interestingly, at no point here did the battery actually reach 100%, but everything got going anyway and the car got about 3.5 kwh before it got pretty dull.

From 12.30 till 4 pm there wasn't enough excess to satisfy the Zappi, but the Eddi got the lot and brought the water back up to temperature. After the Eddi was sated there was a bit of export, but the sun was coming back out even though it was lower and no longer at a good angle to the panels, and the Zappi had another three shots at charging. The first time it went a bit mad, getting as much again from the battery as it was getting from the solar then cutting out again for no readily apparent reason. Then it did much the same thing again. The third charge seemed to "take" and was maintained until the battery was down to 94% again. Altogether, for the day, despite the cloud cover, the car got 6.2 kWh and the SoC went from 81% to 92%.

At the end of the day the system took an unusually long time to stop the Zappi, importing from the grid to replace even more than what the battery was no longer giving it, but in fact it was only 30-45 seconds before it sorted itself out and the actual amount of electricity involved was 0.12 kWh.

After that there was no chance of the car charging again as the issue wasn't cloud cover, it was the sun beginning to go down. However there was still a fair bit of excess which allowed three things to happen. First the battery recharged all the way. Then the Eddi brought the water back up to temperature. Then I cooked the evening meal. (OK it was just a ready-meal as I was still glued to the tennis, but still, it happened.) Then the battery recharged again. There was even a small amount of export until 8.15, when the house started to call on the battery again. However it was actually 9.45 before the battery fell to 94%, and very fortunately I had remembered, some time between six o'clock when the car stopped charging and then, to spend a whole 15 seconds changing the protected level back to 4%.

It's fine. What's the issue? Other than me forgetting to take a whole 30 seconds out of my life to change the settings in the inverter, what actually could go wrong? What am I missing? Why should I go to the trouble and expense of having the wiring changed, rather than do this?

 

[Rolfe]

Now I'm even more confused. I got into a conversation with a guy I know on Twitter, and he said his system is set up the way mine is, and he prefers it that way. He was managing the daytime charging more hands-on than I was - watching the battery SoC on his phone and intervening manually to shut it off when he didn't want it to go any lower. I said I was simply setting the inverter to protect 93% of the battery and letting it get on with it, then all I had to do was to remember to change that back to 4% some time in the evening before the house needed it. He said, that's brilliant, much the best way, useful tip.

So then I asked him about overnight charging. He said, move the CT clamp. I think someone earlier in the thread also suggested that but I didn't know what he meant. Brian showed me, with a photo of his system, then by looking at a photo of mine. According to him there's no need to do what John proposes, and this simple change which I can do myself will have the same effect.

On questioning him further, he said that he had moved his own CT clamp for exactly the same reasons John and others are putting forward, but preferred it the other way so that he could allow the battery to support solar charging, so he switched it back. He is actually doing what I thought was the answer for overnight charging, setting his home battery to charge at the same time the car is charging. He said that works too. But he also said, if you do want to stop the inverter seeing the Zappi as a legitimate load, moving the CT clamp is the way to do it.

So if it's that simple, and it's something I can do myself in about five minutes, and even undo again if I want to, why all this talk about a second consumer unit and "tails" and rewiring the system? Every time I think I understand this, someone throws a curveball.

 

[GaryMG4]

Now I'm even more confused. I got into a conversation with a guy I know on Twitter, and he said his system is set up the way mine is, and he prefers it that way. He was managing the daytime charging more hands-on than I was - watching the battery SoC on his phone and intervening manually to shut it off when he didn't want it to go any lower. I said I was simply setting the inverter to protect 93% of the battery and letting it get on with it, then all I had to do was to remember to change that back to 4% some time in the evening before the house needed it. He said, that's brilliant, much the best way, useful tip.

So then I asked him about overnight charging. He said, move the CT clamp. I think someone earlier in the thread also suggested that but I didn't know what he meant. Brian showed me, with a photo of his system, then by looking at a photo of mine. According to him there's no need to do what John proposes, and this simple change which I can do myself will have the same effect.

On questioning him further, he said that he had moved his own CT clamp for exactly the same reasons John and others are putting forward, but preferred it the other way so that he could allow the battery to support solar charging, so he switched it back. He is actually doing what I thought was the answer for overnight charging, setting his home battery to charge at the same time the car is charging. He said that works too. But he also said, if you do want to stop the inverter seeing the Zappi as a legitimate load, moving the CT clamp is the way to do it.

So if it's that simple, and it's something I can do myself in about five minutes, and even undo again if I want to, why all this talk about a second consumer unit and "tails" and rewiring the system? Every time I think I understand this, someone throws a curveball.

I think if you have a method that works for you while you are waiting for the G99, then just do that as I suspect you will approaching it differently once you are getting paid for the excess. Then again it may change again in the depths of winter.

 

[Rolfe]

Yes, you're right, and I need to chase up this G99. I think it will all get a lot simpler then. And even cheaper. But I still need to understand overnight charging properly, because I've never done it on purpose (plenty solar) and both times it happened by accident (apps doing things I didn't know they were going to do) my home battery was sucked dry.

Will all be well if I simply set the home battery to charge while the car is charging? What if some of the scheduled charge is outwith the cheap rate?

Does simply moving that clamp do the same as the professional rewiring job with a second consumer unit that John was recommending? If so, why go for the latter? If not, what are the advantages? (I wish John would explain, but he seems to have disengaged. Maybe someone else who understands what he's saying can.)

It's all a learning curve, and hopefully in a few weeks I'll have got my head round it well enough just to leave it alone to follow its routine.

 

[GaryMG4]

I'm already doing what I expected to do in the winter as the solar generation has been so poor this month. Last year I was able to just plug in the granny on a sunny day and add 10-15 kWh but only buy 1-2 from the mains due to clouds and house load, but at the moment it's closer to buying 8-10. I've just switched to Go, so 5 hours on the granny costs around 90p and adds around 18%. This would be fine in the winter when my mileage drops off, in the summer it means I need to do it a few nights in a row.
My understanding of using IOG is that you treat charging as if you don't have solar and just let it smart charge on cheap overnight electricity only, sell all your solar, charge your battery on cheap overnight. The interesting bit is what will happen if during the cheap period your battery reaches full charge and the car is still charging, will the battery try to provide the power?

 

[Rolfe]

That's a whole new way of working I hadn't considered. Going right back to the beginning of the thread, the starting point for all this is that I wanted a charger because I wanted to be able to charge faster than the granny lead could provide. But I do see it as a way of getting a bit extra from the house battery into the car in appropriate circumstances.

I do intend to move to charging overnight and export the solar when I get the chance! As you say, what happens when the battery is at 100% and the car is still charging? If it tried to provide the power then it would drop below 100% and go back to charging...? I'll try it and find out. What's the worst that could happen? An empty home battery on a day when there's very little solar, that's all. But even a dull day in summer can usually support the house for 12 hours and put a bit into the battery, so it's hardly a tragedy.

I'm still baffled by the CT clamp thing. I can see what to do, Brian explained it clearly to me, and he says it will have exactly the same result as rewiring and adding in a second consumer unit as John was suggesting. So if that's your objective, why not just move the clamp? Why all the talk about a much more major intervention that needs a qualified electrician to do it?

 

[GaryMG4]

I think the idea of a second CU ia that you use Henley blocks to split in incoming power before it goes to your house CU so the tap for the Zappi happened before your house CU that way the battery (CT clamp) which is on the feed into the house CU cannot 'see' the Zappi load and therefore will not attempt to provide it. I presume your Zappi is currently wired through the house CU? The Zappi CT clamp is primarily there to throttle the Zappi in the case where it and the house load is approaching the limit set by your DNO fuse.
I'm not sure which clamp he is suggesting moving, or from where to where.

 

[Rolfe]

It might have been in the other thread where John raised the issue again, or maybe in a DM conversation I was having with Coulomb. I thought one of the videos also mentioned it.

Well, I'll work it out at some point! Brian says I can't do any actual harm and if I get it wrong just move the clamp back to where it was.

Right now the car is charging well on intermittent sunshine, the gaps in the solar being bridged by the battery. It really does work well, and although I set the inverter to protect 93% it hasn't fallen below 95% all morning, the charge has been continuous even through a cloudy half hour and it's already added 6 kwh in less than two and a half hours.

This is the earliest I've seen the car start to charge - about eight o'clock. Yesterday I had a new fridge installed, because the old one has been trying to die for several months. It's drawing less power than the old faulty one, with the result that my home battery only fell to 84% overnight and so was charged up sooner, letting the car at the sunbeams an hour earlier.

This is good because I drove almost 100 miles yesterday evening and I'm planning on doing the same tomorrow evening, followed by 60 miles on Friday morning. It will be quite fun to see if I can do it all on sunshine and so postpone the experiments with overnight charging even longer.

 

[GaryMG4]

Today is probably the first day this month when I've tried to add sunshine, done a fair few miles and all of it has been on Go rates. But although its been fairly sunny the 7kWh I've added has still cost around 70p so more expensive than Go.

 

[johnb80]

Today is probably the first day this month when I've tried to add sunshine, done a fair few miles and all of it has been on Go rates. But although its been fairly sunny the 7kWh I've added has still cost around 70p so more expensive than Go.

How did you incur the 70p cost?

 

[GaryMG4]

How did you incur the 70p cost?

Grid topping up over the solar due to cloud cover.

 

[johnb80]

Grid topping up over the solar due to cloud cover.

Ah ok, do you not have a wallbox that can follow the export level (Or just not configured it)?

 

[Rolfe]

The weather forecast for today wasn't all that promising and I got back late last night on 44%. But hey, managed to get 23 kwh into the car anyway. No cost at all when tiding the charger over the cloudy periods because the battery supported the charger when that happened, then recharged when the sun came back out, in parallel with the car charging. Which is kind of what we were talking about.

The house battery only discharged to 81% because the installation of a new fridge on Tuesday has reduced the base house load significantly. Enough solar to allow the battery to start charging at the back of six, and there was a fair bit of sun so it was well charged by eight. The Eddi started to heat the water, but by 8.15 there was enough solar to power the Zappi and it woke up.

I didn't actually wake up till nine (it was a good night!) and when I checked all was going perfectly. I spent a whole 15 seconds flipping the protected battery % to 93%, and let it get on with it. Everything was fine and the battery never in fact dropped below 94% despite quite a lot of cloud at times. I jinxed the whole thing by boiling the kettle for a coffee at 2.30, at a point when the solar was really low, so there wasn't enough excess to keep the Zappi going. (I wasn't paying attention, but if I'd waited half an hour till the sun came back out the charge probably wouldn't have stopped.) However, the battery recharged for a bit, then the Eddi had a go, and half an hour after cutting the charge the Zappi re-started.

At 4.30 I pulled the plug because I had to take the car out for an hour. It was getting to the point where there wasn't enough solar to make it worth continuing anyway. After that the solar was taken up by the Eddi again, with another bit of kettle-boiling around six.

It's all completely seamless. There's no chance of the battery draining, because if it suddenly gets (and remains) very dull the battery will stop supporting the Zappi when it gets to 93% (or wherever I set it), and the remaining solar will be redirected to recharging the battery. Same if it's still charging when the solar fades in the evening, or indeed if the ramping-up phenomenon I have not yet seen starts to happen.

I am UTTERLY BAFFLED as to why this work-round isn't acceptable. I much prefer it to having the Zappi repeatedly cut out when the sun goes behind a cloud, or indeed to importing peak-rate mains electricity to tide the Zappi over these periods instead.

I've just realised that my car hasn't tasted a drop of mains electricity since I got back from my road trip some time in May. All very satisfying.

 

[decrep]

Did somebody mention a Zappi mod that stops ramping? Maybe you have that.

 

[GaryMG4]

Ah ok, do you not have a wallbox that can follow the export level (Or just not configured it)?

Correct, and with a nominal 4kW array it doest take a lot to the drop excess below 1.4kw. At least with FiT I still get 23p per kWh even if I use it so in truth the 70p was probably covered by the FiT payment.

 

[Rolfe]

Did somebody mention a Zappi mod that stops ramping? Maybe you have that.

I don't really know anything about it. I've never seen my Zappi try to do it, but I don't know how common it is or what circumstances are likely to cause it.

I just set the inverter to protect 93% of the battery while the car is charging directly from the solar. Even if it tries it, it's not going to get very far.