18650 Garden-Powerwall with 50KWh in Germany

the last two weeks I finished my powerwall project. On the ToDO list:

28 batterie packs 60p
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At the end it's more effort then the bigger 120p packs because of twice of the amount of busbars
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I solder the fuse wire in one piece and at the end I cut the unnecessary pieces
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almost ready
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just need to solder the fuse-wires to the busbars
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next step: balancing all the packs
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pretty dangerous so close together, I do recommend not to do so
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for me it works well but I_ve done this just several times
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on the other side there are sitting the 120p packs, but they need some time to balance too
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after 48h of balancing the 60p are balanced and ready for installation
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they will support the 11KWh system at the pigsty
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all wires are 16mm² as well as the busbars
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I decided to take the BMS plate out again and make a modification
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I want to add a external voltmeter to the locker so I can see the battery status while walking past the locker without connecting to the bluetooth app, so I have to add a shunt
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then back again with the bms and with all battery packs. Two systems with 14s60p each fits into one compartment
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next is to customize the bms wiring harness
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on the right side the two older systems, left the two new with identical capacity
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at the app there are four systems now
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because the voltages didn't fit there is a huge current at the moment of adding the two new systems to the older ones
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4,5V difference.
But it doesn't matter, all cables and BMS are good for 60A continous current
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after installing the battery packs I want to add a voltmeter too
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the "Dremel" clone works well with the good grind discs from a dental supply
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on this picture the display is with default settings therefore the battery status is wrong, you have to manually set the max and min voltage first
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last step is to complete the fire safe insulation. Now, the system in the pigsty is finished
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next step: the other system at the garden shed
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to the already existing two systems of 14s120 there comes another 14s120p
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I add a shunt too
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it's designed for 200A. Each battery system will be limited to 120A
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cables and busbars in 35mm² copper
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the bms wiring harness has to be extended
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just stuck together, without some cable management at this point
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here we go, the three systems inside the locker at the garden shed
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the moment of connecting
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now that it works I can do some cable management
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cables for the voltmeter
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and the front insulation
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now three of a total of four compartments are fully equipped (the smaller locker in the pigsty has one compartement left too)
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So, now at this point I finish my powerwall project because weather is getting better and I have lots of plans for my garden.

At the end here are some facts summed up
  • 75KWh of usable capacity
  • 10.800 cells 18650 from used and defective laptop and ebike batteries
  • voltage range single cells: 3,30 - 4,05V
  • voltage range 14s systems: 46,0 - 56,6V (exception: 16s system at the garage)
  • maximum total output power: 16,4KW
  • duration of this project: 11 month -> very first start was in april last year

Thanks a lot to pete for his videos with very good explanations and the possibility to take part of the whole building process, this definitely encourages people which are new to this things to get it on. And for this community too.

I learned lots of things from this YT channels and can't recommend them strong enough to others
 
Hey Stefan, great thread. Do you use the current limiting function on the BMS?
I'm planning to start my first build with a 14S80p pack, but I want to limit the current in my packs to 500mA per cell, thus max 40A in this stack. I plan to upgrade my packs in the future when I have enough cells, to add another 14S80 pack and be able to pull 80A total. I want to buy a 5KVA inverter for my future plans already, I know I can limit the current there, but when I extend the packs I don't want it drawing more current from this pack, since I don't know what cells I'll get I might go for a bigger or smaller pack in the future.
 
Hi. I guess the BMS can't limit the current in the way you want to.
The value "max. current" is a hard limit like a fuse, not a limitation which smoothly drops the current down to this value.

If the "max current" is higher then the value you set (for at least 10 seconds or so) then the bms will go into safe mode and cut off the load.
After 60 seconds it will release the load again an if it exceeds the "max current" again it will cut it off again.
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Amazing Stefan, I "watched" the whole post as if it was a documentary. And thanks for writing the descriptions and model number of the pieces you used, I took note and will try to find them over here where I live 💯 :giggle:
 
Hi
I love your project :)
About PowerWall Bracket, is 2mm steel plate is enough to hold battery packs or need more or less thickness ?
i have 3900 cells (13S10P x 30) to fix on the wall ;-)
Thanks a lot
 
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cheap plasma cutter, see on the second page of this thread:
 
this is the status from the last weekend
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next week I will add the wires, bms and so on.
This looks great. Very nice work! 😃 Very fireproof.

Are you still happy with the locker solutions? Easy to maintain?

Do you have a fan inside?

Is it possible to use screws instead of welding the shelves?
 
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