Scruds first powerwall

Scrud

New member
Joined
May 15, 2018
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2
I've been lurking on this forum, youtube, and the facebook group for a long time gradually learning about powerwalls. Eventually I got to a point where i was ready to build up a system. I wanted to start with something fairly cheap and small scale, since I have limited solar panel space at the moment. Just enough to provide some free energy for running low power equipment around the house like my fishtank, and charge phones/tablets/batteries.


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I bought a few lots of new old stock dell laptop packs and got to work stripping them down.


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A fairly tall heap of cells.


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My humble testing station. Most of the cells were very close in voltage, so i was able to parallel charge them on the imax, then run capacity testing on the opus. Testing 300+ cells on a single opus took a long time. Overall, i think there was only 15-20 cells that had to be binned. Unfortunately i didn't order enough cells to keep all the cells i used over 2000 MAH, but they still averaged well above that capacity.



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Some DIY entertainment while i solder my packs up. I used 12 AWG solid core wire for the bus bars, some scrap stranded wire for the negative connections, and some 1 amp glass fuses on the positive side. I haven't had any issues with the 12 AWG bus bar, but i think next time around I'll go with something larger.


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First solar/discharge test. I went with a cheap amazon solar controller to keep costs down, so far it's worked fine for my application. I used 12 AWG silicone wire to connect the packs, and 30 amp Anderson connectors. Again, no issues here but next time around I'll be using thicker gauge cable and connectors.


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Renting makes setting up solar panels very difficult. I have 2x 100w panels in parallel. I eventually laid these out in a more efficient angle, but the balcony roof really restricts the amount of daylight. I end up running the battery under a light load (50-150w) until the battery drains down, then disconnect the load for a few days to let the panels recharge the batteries. Better than nothing i guess.


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Girlfriend designed and 3d printed a faceplate for me to mount my voltage monitors, switches, and solar input on.


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Keeping costs down, i mounted everything in an old cooler i wasn't using anymore. Not particularly worried about temps or airflow, as i'm not pulling a lot of amps out of this setup. It does take up more room than necessary, i could easily fit another 3s in here.


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Wired up a 12v panel intended for auto/boat use. I chose to go with a cheap car inverter to run some AC devices to save money for the project.


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Complete install. Used various DC breakers designed for car audio installs, and Soldered up a balance lead so i could balance my pack with a smart charger if things started to get out of balance. I was initially worried about not running a dedicated BMS, but i was very careful to distribute the capacity of cells evenly between all 3 packs. In over 6 months of use, i haven't needed to re-balance once.


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Drilled some banana plug connectors to run 12v devices off. I can now charge 18650's with 18650's!


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Infinite energy hack? :p

Overall i learned a lot from this project and i'm happy with how it turned out. I'm impressed with the capacity i was able to pull off (estimated 2.25-ish KWH) on such a small budget. I do wish i would have gone with a 4s setup instead of 3s, but it still works "well enough". I am now in the process of building out a 48v (14s 100p) powerwall with a proper inverter, batrium bms, and MPPT charge controller. This setup will probably be torn down and rebuilt into a more compact and portable 4s setup to be used during camping trips.
 
Nice setup. Kewl idea using the cooler ;)

If it does get too warm, you could always just put two computer fans on the lid. One facing in, the other out. Or I suppose you could put one on either end behind the handles.
 
hmm you look like you need cell overs hint hint wink wink...


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Korishan said:
Nice setup. Kewl idea using the cooler ;)

If it does get too warm, you could always just put two computer fans on the lid. One facing in, the other out. Or I suppose you could put one on either end behind the handles.

Agreed the cooler makes a great case. However, I would definitely keep an eye on temperature. As the cooler is designed to be an insulator, it will surely hold the heat. I would definitely opt for some kind of cooling solution.
 
Geek said:
Korishan said:
Nice setup. Kewl idea using the cooler ;)

If it does get too warm, you could always just put two computer fans on the lid. One facing in, the other out. Or I suppose you could put one on either end behind the handles.

Agreed the cooler makes a great case. However, I would definitely keep an eye on temperature. As the cooler is designed to be an insulator, it will surely hold the heat. I would definitely opt for some kind of cooling solution.

The cooler was more of a "I need to put these batteries inside something without spending money" solution. It's not very space efficient, and doesn't offer much protection. It is technically an insulator, but not a very good one, plus the cells aren't pushed very hard at all. My cheap inverter limits me to 10-15 amps at 12v (150w), and with my inefficient panel setup, my charge amperage is well below 100w. After 6+ months of use, I've never seen the cooler warm up on the inside, so I'm not planning on adding any active cooling. I think a complete rebuild of the pack to get 4s in a smaller more portable/durable package is the next step for this project.
 
Very nice build. Clean. I like the 3d printed parts also. Looks very professional. Its nice when something works as planned :) . I don't get that very often lol.
 
@tremors: Very nice printed cells cover. Will you share your STL somewhere ? I would be very keen to print some for one of my ongoing project (Soon a new thread on the forum)
 
Sholphin02 said:
@tremors: Very nice printed cells cover. Will you share your STL somewhere ? I would be very keen to print some for one of my ongoing project (Soon a new thread on the forum)

+1 for the STL :)
 
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