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@anthropy @aris You know very well I am not talking about base materials such as the LiFePo4 here, which the average consumer shouldn't even know. But what it is put in, it's certification and the certification, safety and requirements of the full installation and what you are connecting it to.
You do you, but mains and high voltage DC electricity is not a toy. 
@anthropy @aris Do take into account your time and what you are getting into, that it's still not finished is an indicator how much worth it can be.
But also I quite frankly find it a bit dangerous what you are preaching to just get any random stuff from China without approvals. (I guess it wasn't apparent) Consider what risk you are taking and comfortable with.
@anthropy It already is on a overspecced cable, there is something really think going there saying 50A or something on it, but it's not helping much. xD
And yeah, I can put all my energy users on that phase and rewire half my house LOL, that ain't easy either and can cause other issues. There is a reason why this is no longer an allowed setup, with a 3 phase inverter the export resistance is a sqrt3 of a single phase and it doesn't cause grid imbalance. A modern smart inverter can probably even generate more power to one phase based on usage perhaps?
Anyway all expensive solutions with the economically cheapest solution still being to just disconnect the solar panels and perhaps get rid of them is insane. >.>
Off grid is cool and makes sense with all the issues, but also feels like giving up and definitely a bit shady for a city house. All because our government sucked at anticipating the energy transition.
@anthropy I know how these batteries work, yes that is how I would set it up. There is still some issues not solved by it though and it's not exactly according to the rules. But yes a lot cheaper 
Edit: the only thing not coming from the P1-meter directly though is resistance from the grid when it's overloaded. So it would actually need to store even when I am using energy on a different phase to prevent the solar panels from completely shutting down >.>
@anthropy I know you mean well, but best to stay with single phase battery instead of plugging in 3 batteries in different phases, still requiring a meter cabinet change and even more difficult and less up to code rewiring keeping a single phase inverter and just pumping power around the house, overloading all cabling. 
Ahaha xD
BTW, a fixed installation can't be taken with you yes, but it is sort of part of the house value so. 
We still got to see, but probably one somewhat larger battery that can perhaps stop most exporting so we don't have to pay is the simplest solution and when we want to use it in the evening the grid is not overloaded anymore would be the simplest solution, even if it's not approved. At least till one of our inverters dies of old age.
@anthropy Yeah, I am going to look at one of those however they have the downside that they are single phase. If I am a good boy and register the change I also need to register my current non-certified equipment and that probably won't end well. Plus the inverter is near the end of the life cycle already.
So we are still doubting between doing the legal/right thing of replacing this setup with an inverter/solar combo that is at least on the approved list or just being a bad citizen and take the risk. Going only single phase there are some cheaper options, but cause it causes grid imbalance not something too good and it will not solve our problems of dropout when the grid capacity is exceeded.
Our power company offers as solution for 7000 euro, excl. the needed additional costs for the meter cabinet (which I am definitely not touching and needs full replacement) something. I do think it is what most people will be looking at as an indication.
We will be leaning to something not so 'right' because it's insane, but at the same time my partner works for the grid provider... xD Perhaps his employer might be able to help do it right and chip in (though in exchange for privacy, they want all data then).
It's a messed up situation for sure though that everyone with solar panels will need to navigate within a year. xD
@anthropy @TechConnectify Simply answered: my house is not off grid nor do I want that. But just getting this professionally done, for sanity but also following guidelines for insurance etc. blows up the costs. Electricians are not cheap to start with.
@anthropy @TechConnectify The panels themselves are yeah, but due to decisions in politics we do face the fact the energy they produce can become worthless without a battery or a way to control them. So even though I got solar panels already I need to look into a several thousand euro investment to not pay for them being there that is very unlikely to pay back soon...
There is environmental reasons why I will, money just ain't everything with solar in The Netherlands at the moment.
@Purple Yeah, sounds familiar sadly. One day one of my colleagues can write perfect high quality code and the next day I am looking at a PR and the WTF/min is incredibly high and I know what happened... When confronted in the way if "I am not really sure why you wrote it like this, normally you have a very different style" they admit they used AI that day cause they were lazy...
And it's often very obviously weird stuff... Like for example we always program Python with typing and suddenly there is no typing anywhere to be found. Recently I even got a PR where >everything< was done using getattr meta-programming instead of typed property access and that >should< be something you almost never need to use and wonder when reading even once.
I really like my colleagues and normally they can make wonderful stuff, but when things like this happen... I don't know, they just given up or something? 