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Greetings from a new member from The Netherlands
Hello everybody!
Just a little introduction about myself. I’m Stijn, 31 years old and I’m living together with my girlfriend in The Netherlands (aka Holland). I’m a Dutchy so I’m not native English speaker, please excuse the English/grammatical errors. I’ve got an degree in electronics and I’m working as an electronical hardware engineer and design/calculate/draw industrial automation installations. I’m also a volunteer firefighter here in our town and like to go scuba diving in the weekends. If there is some free time somewhere in my week I like to build all kind of electrical project, like the one I’m planning on doing now.

I’m planning to install 9 solar panels on the roof of the garage soon, with a basic Victron based powerwall/inverter for now and expand it in the years to follow (12 panels on the terrace roof, 3-6 on the house roof). For now I’ll probably use some car batteries because the Victron system needs a battery to run but the first couple of hundred 18650 are already tested (photo of my testbench below) and I will receive the next 2000 next week. The plan is to build a 14S100P pack in a couple of years and expand it with more parallel 14S100P packs. Building the battery system right now isn’t profitable because of the “salderingsregeling” (google translate says: netting arrangement?) we have in The Netherlands, but this advantage will start to reduce after 2022 and decrease in the years after that (short explanation below in this post).
Ivel posted a detailed plan with schematics, 3D drawings and calculations of the complete planned system very soon and would like to hear your opinions on the system I’m planning to build and what can be improved. Especially people with experience with Victron equipment, and people from The Netherlands with knowledge about local laws and regulations.  But all help is welcome of course! Link: If there are enough people who want to follow the build I can do some build/project updates, but please bear in mind it’s a multiyear project.
If you have any questions please ask them and I will answer them as soon as possible.
So far my “little introduction” haha, sorry!

Short explanation about the “salderingsregeling” in The Netherlands:
Most houses use “smart energy meters” which measure the energy used and the energy delivered back to the grid (for each phase if you have a 3 phase connection). Currently the generated solar power is deducted from the used power on a yearly bases. For example, if you generate 1.500kWh and deliver it back to the grid and use 5.000kWh you only have to pay for the 3.5000kWh. So for the next two year I already have a “free” battery (I still have to pay a yearly fee, like every household). But in 2023 this will reduced to 91%, 2024 82%, 2025 73% down to 0% in 2031.
Bigfoot48 likes this post
Who's this guy? Introduction
What's he doing here? Project Design
Welcome and I will be following your topic Smile

Can I ask where you source your 18650's? The prices of 18650's are slowly dropping on Marktplaats but still expensive Smile
Thank you Bigfoot48!

The prices on used individual cells can be ridiculous high indeed, 1-2 euro a piece. Sometimes there are cheaper ones but they are mostly already tested and have a capacity of less than 1800mA.

The first 100-ish cells I got from a local company selling (electric) bicycles, he allowed me to go through the box of defective and replaced e-bike batteries. I've got like 100 cells from the company I work at just going through the old battery box containing old laptop batteries and power tool batteries. All in all the yield of this is only 50 usable cells, because of high internal resistance, low capacity of <2000mA or less then 80% of the original capacity rules I use.

I did buy 50 Lenovo laptop batteries on ‘Marktplaats’ (Dutch Ebay) containing 300 cells in total, but that was a bad buy, only 50 cell yield after 200 tested. A part was rusted/leaking and another park where already at <1V or 0V so they went straight to the recycle bin, and the rest didn’t have enough capacity (mostly Sanyo UR18650ZY) or are heaters (mostly LG LGABB41865). Still 100 or so to test but my hopes aren’t very high.

The 2000 cells I’m going to pick up in a couple of days look great on the photo’s and the random test numbers look great. The cells are already extracted from the packs so no surprises in rusty/leaking cells I hope.

The other places I want to visit and ask if I can have the 18650 battery packs are other local bike shops (4-5 of them in my town), some large locally based companies with a lot of employees using laptops, local and surrounding town yards where local resident can recycle stuff and of course Ebay (Marktplaats) like sites.
Who's this guy? Introduction
What's he doing here? Project Design
Can I ask how you start your conversation with bike-shop? Do you offer money for the packs or do you keep that as a last resort.

I feel some internal resistance to walk into a store and ask immediately about defective cell packs. It's all about a good start that get you somewhere.
For them it's easier to say no and be done with it.

I'm receiving some laptop batteries, but the new ones are flat and contain pouches, 3 of them. They are 4500mAh rated, but still need to extract them, most of the time 1 or 2 are faulty and the left one(s) are still good. It's easy to identify, the swell up like crazy. Only disassembly is a pain, the short fuse real easily.

But all the other laptop packs I have the same problem, only ~5% is good, the rest is just waste.

Bought recently on Marktplaats 10sp2 packs, 20 packs for €100,- but leaking cells and remaining capacity of 1200 mAh or lower took out the fun.
Bought from the same guy 100 cells for €45,- he advertised with 2200mAh, I'm testing them and I think he is testing the capacity in the wrong way by just charge them and not by discharging them.
But also only a handful make the 2000mAh mark.

So the search continues to find a good source Undecided
Hey Stijn another Dutchy Big Grin  nice to see another dutchman building a powerwall.
Our source of 18650 is a bit low here in the Netherlands becouse the recycling company's (scherpenzeel Lelystad) and when you find them they are very expencive or bad sells the best way is to get them is talk to bike stores and give them some money

* A little more explination of our "net metering" here in the Netherlands

Our electric rate is 0.24 euro cents for 1 KW equals to 0.28 US cents so for every KW we use and give back to the grid is 0.24 cents but in a few years from now we get less and less back for "OUR!!!" electric and investment... but the funny thing is, we getting less back for the kw we send back to the grid but the FREE electric that they get other people has to pay 0.24 cents for the electric they get for free...
In the meantime I picked up the 2000 cells (the seller found some more battery packs I could have too, and I counted almost 2600 cells), a part are under the 2000mAh, but doing a fast count I counted almost 1800 cells with 2000mAh+ capacity. I've tested the first 100 cells and the average capacity now is 2750mAh.

I've asked only one bike shop owner so far do be honest who donated like 20 battery packs, unfortunately I could only use one battery pack (70 cells average 2790mAh), the rest where NiMh, NiCad or Li-ion pouch cells. Not really a great example, besides owning/running the bike shop he's also a colleague volunteer fire fighter.

But to answer your question, I would just walk in and explain I’m building my own (Tesla) powerwall and could use certain old e-bike batteries. Most e-bike shops get a couple of euro’s for every kilo of old batteries. I don’t know the exact rate to be honest, but you could match that or pay a bit more.

I found my good source on Marktplaats for now, I need 1400 cells and I’m confident I have them already (although untested), but I’m still watching Marktplaats/Ebay to see if there are any good deals for my second 14S100P pack because I don’t have 2800 cells yet.
Who's this guy? Introduction
What's he doing here? Project Design
That is a very nice start Smile

May I ask how much did you pay for them?

How are you planning to build your pack? Spotweld them or a busbar and use fuse wire?
I paid 600 euro's for the the (almost) 2600 cells. Still a lot of money but it's "only" 0,23 per cell.

I'm not really sure about the design yet. I definitely need some kind of busbar for the higher current part but I think i'm going to fuse wire the individual cells. It's a lot of work but I kind of like the individual cell fuse idea in case something is wrong with the cell. I do have a spotwelder so I'll probably spotweld the fuse wire on the cells so I don't have to solder and heat the cells unnecessary.
The 14 individual battery pack designs are dependent on the battery housing. If it's possible I would like to go with a long and narrow pack (4 wide, 25 long) but I'll have to see when what's going to fit when I got a good weatherproof housing.

In case you didn't see it yet; I've posted my project design last night and put a link in the start post. It's a long read but there is a lot of design information in there.
Who's this guy? Introduction
What's he doing here? Project Design
Welcome ~

SLA car batteries are totally unsuited for powerwall uses, going bad really quickly when left at intermediate charge levels, or doing deep charge/discharge cycles. They'll probably go bad within a few months, depending on usage.
Perhaps you can get your hands on a smallish 12V lithium car/motorcycle battery until you have your 18650s ready? Those should last for years.
Other "less worse" options are "Marine" (aka "semi-deep cycle") batteries, and of course "deep cycle" batteries... but they usually cost heaps more.
Modular PowerShelf using 3D printed packs.  60kWh and growing.
That is a very nice start Smile.

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