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vienna wall build
#1
Hi guys,

As i am on this forum for some few months now, i‘d like to introduce myself. My name is karl and i live nearby vienna in our own house. I am in renewables business for quite some time now but primarily wind energy.

I am considering getting a pv installed on our house for some time now and will get it done this year. First i planned installing 5kWp but will now go for a 10kWp plant due to a high probability of buying an electric secondary car within the next two years and just 5kWp may suck then. We get subsidies in austria which leads to round about 10k for the 10kWp plant, which is quite ok.

Battery storage is also a topic i am watching out for some time now, also from a professional/job point of view. It is a big topic in UK and GER for grid support and prices come down dramatically. In germany there is a lot of rental models for home pv and newly storage coming up as well.

In austria, we are quite lucky with much lower electricity prices than in germany. We pay round about 20cent instead of 30cents in germany. This is good for us but destroys any business case for storage.

On the other hand i run my cooling system, my irrigation pump as well as my pond pump besides the standard stuff in summer and i have nights where i consume more than 10kWh. I can‘t run irrigation during the day, because it takes roughly 8h in total and kids are playing during the day in the garden.

Beside that a typical 6-7kWh battery storage is way to small it is already way too expensive.

When googling around i found the diypowerwalls forum and was 18650ed as average joe is saying (i think he is holding intellectual property on that *ggg*)

Cell Harvesting
I started searching for cells and even found a lot of places where they had them but finally they couldn‘t give them to me due to waste regulations that force them to document the whole process for more or less every battery pack that has to be binned... What i still don‘t understand why they can‘t sell them to privates just as used and not as defective... 

But finally i found some batterypack repair shops and ebike shops who were willing to give them to me. First 2kWh on defective packs i got for eur 100,- per kWh including shipping which was ok at that time to get started but is not ok in the long run. A second repair shop sold it for 70,- including shipping. And then i found my favourite, an ebike shop who is building its own bikes and also handles guarantee claims themselves. They seem to be quite successful selling bikes because they get back 50 to 60 batterypacks (each 400-500Wh) a year and i got them to give me returned backs for free... *yeah*

Typically the cells are Samsung or Sony high drain cells which are in the area of 2000-2200 mAh. Roughly 90% of these cells were tested fine. 

Charging
I started testing with 2 accupower IQ328+ but i realized that it would be taking me ages to test 2000 cells or more. Then i ordered 2 opus but still was not very effective. I started my attempts to build an automated arduino/ESP32 charger but decided to go - from my point of view - for the most effective solution and bought 10 liitokala 500 chargers. I‘ve got them in china for EUR 13,- each (4 bays) which is slightly more than EUR 3,-for one bay. Attached to a 40Amp power source it started to make fun. I know it is not optimal to use different types of chargers but i took that risk. In total i do have 14 chargers now. In general I don’t mind whether the liitokala is testing too high or too low as long as all cells are tested on the same type of charger. Even with my mixed setup of chargers my 80p packs are alle 150Ah (4.1 - 3.2V) +-2Ah, though very fine. 

Pre-charging was done on a self built TP4056 10 bay charger. I also did pre-charging with an icharger 208b which is a very cool and versatile thingy, i love it. I also do charging and discharging of 80p packs with it and it works very well. Discharging is done with an external 0.15Ohm 200W resistor setup on a large heat sink.

After first capacity check i put cells in boxes for at least one week and checked voltage again after that and cells that were below 4.15V were charged up again to 4.2V, put in a box aside for longer time and voltage checked again and sorted out when they had again below 4.15. When they had below 4.0v they were binned.

Cell sorting
At the very beginning i was noting the exact mAh on each cell and throughout the process i decided to round mAh up or down on full hundreds. Every test-cycle shows slightly different countings and why not approach it a bit more pragmatic. I was planning to fill my own cell-database but finally didn‘t do it because it is not necessary for the pure package-building.

Pack building
I purchased the typical 5x4 cell holders on aliexpress and decided to build 15packs each 80cells, where 14 packs will go into my powerwall and the extra one will be a spare one for replacement of one of the 14packs at some point in time...
As a bus bar i am using 3x2.5mm2 threaded copper wire, which you can buy at stores like hornbach as a single wire, which just needs dismantling and drilling. I am having a lot of it lying around from our house-building time.
I do use 0.2mm fuse wire which should be good for 5 amp current and the wire is soldered. Therefore I do use my 60W soldering station with a chunky tip.

I put together the holders for 80p and spread my before in 100mAh steps sorted cells evenly on the 15 packs. I have tested 5 packs now and all of them have 150Ah +-2Ah.

Installation
I will put 14packs next to each other to the wall in my garage with clips and bolt them together in series with M8 screws. I will cover the batteries with a housing to be able to control temperature, especially in winter because my garage is not heated and temp can go below 0°C.

Inverter
Most probably I will use the same 10kW hybrid inverter, that daromer is using. 

Next steps
- finish pack building
- develop voltage and temperature control with esp32
- develop top balancing with esp32
- develop heating element controlled by esp32
- collect batteries for a further 14s80p setup
- play around with building my own arduino/esp32 charger... :-)
DK100 and Solexx X like this post
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#2
Looks like you have it all planned out very well... 
Now we need some pics.  Smile
___________________________________
18x 300Wp solar off grid and 10x 180Wp solar tracker grid-tie
10KW 3phase hybrid inverter. 40Kwh 18650 storage (for now)
My setup: https://secondlifestorage.com/t-Instant-powerwall
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#3
coming soon ;-)
hbpowerwall likes this post
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#4
Why not buy a Batrium BMS?

Oh, and pictures definitely Smile
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#5
Batrium... i don’t know yet... i like the fun of building my own but batrium has definitely a lot of pro‘s

I am hassling with uploading pictures from my phone due to max size of 2mb... pics will follow  Cool
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#6
Download a photo resizing app so you can resize it under 2mb
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#7
Hi, 
Here are some fotos of my build. 15packs, each 80p with 150Ah are built. I have built one spare pack for later replacement and will do so for further expansions...

I have just received another 3000 cells from ebike and have just started testing process. But I have to care about getting my own PV on the roof, otherwise it doesn‘t make much sense  Wink 

In total it will be then >30kWh of 18650‘s. 

And yes, I think batrium will be my choice as a BMS. 

I will then have 14sf80p and probably 14s200p. Are there any suggestions how I should combine packs. All of them on one string (14 longmons only) to the inverter or two separate strings which also means 28 longmons or even more spread...?

Here are some pictures of my first 8.5kWh packs. Cool thing, I had enough of the Samsung cells in order to have all packs in the same colour...

Best regards
Karl
hbpowerwall and Solexx X like this post
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#8
Big Grin 
I’m building my second set of 14s80p now  Big Grin
Ibiza, hbpowerwall, mike And 2 others like this post
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#9
Good Googily Schmoogily!! Just don't stack them up like Pete did and have them fall on ya Tongue
Proceed with caution. Knowledge is Power! Literally! Cool 
Knowledge is Power; Absolute Knowledge is Absolutely Shocking!
Certified 18650 Cell Reclamation Technician

Please come join in general chit-chat and randomness at https://discord.gg/c7gJ5uA
(this chat is not directly affiliated with SecondLifeStorage)
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#10
Will keep that in mind... Big Grin
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