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@maruno Also sorry if I came across rough earlier. I was busy and didn't have the mental capacity to get into some debate about the safety of things, and also didn't like the seeming implication that I didn't know what I was doing (I've been doing this for many years and definitely did my research and talked with experts in the field).
If you do want to have an openminded discussion about it I'm all open to it. But.. please don't just berate me with assumptions, it honestly feels condescending.
@aris @maruno Okay I've finished my long working day and I looked around a little.
I decided to be lazy and let Gemini Deep Research gather some intel on the subject, it seems to align with what I remember from my own research: https://gemini.google.com/share/3be8913c4777
One thing that I can immediately agree with from there is that https://nkon.nl is a very good european-based supplier, with cells in the exact price range I mentioned: https://www.nkon.nl/rechargeable/lifepo4/prismatisch.html
so if you DO want to try it, that's the way.
@aris @maruno and that's entirely fair- I'm not saying not to be cautious, but I find it a little much to say that neither of us know anything about this and that I'm "preaching" for unsafe setups, when I've explicitly said I'd have to look into what good cells are later.
Any setup can cause a fire, and I've seen some extremely scary thin wiring and connections in premade bat boxes that are "okay because we probably don't pull that much amps" (youtube is full of these). The key is research tbh.
@maruno @aris The LiFePo4 cells they're selling here for 300 are sourced from china for <100, they're the same cells, you just gotta know which ones to get.
My system is working, batteries and all, and sure I could and want to upgrade it further, but that doesn't mean it can't be something relatively easy to deploy.
@aris @maruno @TechConnectify As long as you have a BMS that is appropriate for the load (overspecced but configurable is okay but make sure to configure it to turn off at the maximum load), it should be fine. It's also worth noting that if you have a low voltage pack (e.g 24V in my case) you have to get really thick cables to carry the amps (48V might be better in that sense).
I'll try see if I can find some good cell manufacturer examples later. For the BMS I personally use Daly.
@aris @maruno @TechConnectify You do have to look around for reputable sellers, because of course the cheapest ones are also cheaply built, but there are very good ones that are also used in cars and such. I'm a bit busy / between things right now but if you look around a little you should be able to find very good *and* affordable ones
@aris @maruno @TechConnectify I actually source them straight from China, because they are the king of LiFePo4; in 2012 ish western manufacturers choose to go with nickel-cobalt chemistries, which are far more expensive, because at the time they had a much bigger capacity per weight. These days they're very similar.
To add, China tried to flood the western markets with cheap EVs but got held back by regulations/taxes so they have a huge oversupply of these batteries and sell them for dirt cheap
@aris @maruno @TechConnectify Batteries are also cheap if you know where to source them, same goes for the inverter; 1.5k sounds like a fancy one, I got two offgrid inverters each capable of 6kW+ for less than 500 a piece, and roughly 15-20kWh worth LiFePo4 cells for 800 ish, a BMS for 250.
I'm guessing my situation made them easier to install though, as I'm putting them down flat on my carport with clamps on the sides, my 5kWp took roughly
5-10 hours. It honestly depends on your situation.
@maruno Off grid doesn't have to be as complicated as it sounds honestly! My inverter is actually a 'bit of both' and can even return energy to the grid if needed.
The main thing you need for offgrid is for the incoming mains, and solar panels, to be diverted to the inverter, and the breaker panel that feeds the rest of the house being connected to that same inverter through a single wire that would otherwise be your mains input. It's basically just 2/3 extra (admittedly chonky) wires.
@maruno well regarding the "overloading": if you put them on less filled power groups you will not have this issue, and honestly most cabling is purposely overspecced; they want you to use 2.5mm^2 cabling for 10-16A but that can easily carry 27A, as example, and you'll find it's hard to get there.
As for solar shutting down due to grid overloading: the only real option there is off-grid unfortunately, your batteries won't cause the grid voltage to drop enough for the inverters to turn back on.
@maruno if you have a rather standard digital meter, it SHOULD in theory be possible to just get the state through the P1 port, see whenever you're starting to send power back to the grid, and put that power into the batteries instead.
The battery I linked you actually has a P1 meter dongle you can just tack on for 25€, which should work with a large share of the meters out there.
but again yea, you can do it any way you want, all I'm saying is it neither has to be expensive, nor complicated 
@maruno I mean, the companies that actively reach out to market a solution to you, are definitely the most expensive options you can get on the market x3;
If you want it cheap and easy: 3x that plug-in battery as example, one per phase, 7.5kWh total, will cost you ~3k, with zero additional costs, AND you can take it with you when you move to a new place.
But it's up to you in the end, perhaps your partner's employer can help, but the cheap options are not the obvious ones usually.
@maruno @TechConnectify It's honestly purely the electrician and convenience that really drives up the costs actually!
If you want a grid tie battery it's even easier, you can buy those plug-in ones that you can plug into any wall socket for around 1k, 2.5kwh (random example from the top of google search results: https://www.homewizard.com/nl/shop/plug-in-battery/ ) of course the more easy you make it for yourself, the more you pay 
convenience costs a lot of money, especially for these kinds things.
@maruno @TechConnectify "wait but 4k is more than 1k"
correct! but I got a good car, you can get those Leafs and similar electric cars for around 2k if you look around a little, and it already got the BMS, charger, etc etc included; you're buying a complete package that you can just start using. If you compare that to having a premade 24kwh powerwall (~2500) installed by a professional (~5k+), then it is indeed cheaper to buy a second hand electric car.
@maruno @TechConnectify To even go further in this: getting a second hand electric car as your battery is even cheaper!
I got a 2013 Nissan Leaf for about 4k half a year ago, 24kWh worth batteries included, less than 70k KM on the odometer, 120KM range.
and I've driven thousands of kilometers to work and other placed in that thing already, so calculating what I saved in gasoline, assuming 6k km, which is about 300-500L gasoline, assuming 1.80€ per liter, is 540-900€, so I'm 1/4-1/2 break even!
@maruno @TechConnectify I built my own 20kWh + 5kW off grid setup, batteries included, for about 2000 euros.
LFP cells cost about 40-100 per kWh, you just have to add a BMS, inverter and some cables.
The expensive part is people. Same goes for the panels; 5kw of panels is 500€, but getting them put on your roof and cabled and all that costs (sometimes tens of) thousands, because there aren't a lot of people who do it and they want a high profit margin.
Happy to show you how to do it though
@TechConnectify I still think it's absolutely crazy how cheap solar panels are
I got my 500w panels, new and unused, for 50-60 a piece, without buying in bulk.
That's cheaper than standard plywood. It's literally CHEAPER to build a house out of SOLAR PANELS than it is to build out of low grade PLYWOOD.
They've gone up a little bit in price since but not much, you can still get 500w panels for around 70 euros a piece, example here: https://www.solar-outlet.nl/zonnepanelen/