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Scruds first powerwall
#1
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.


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


A fairly tall heap of cells.


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.



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.


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.


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.


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


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.


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.


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.


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


Infinite energy hack? Tongue 

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.
Walde, Korishan, wim like this post
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#2
Nice setup. Kewl idea using the cooler Wink

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.
Proceed with caution. Knowledge is Power! Literally! Cool 
Knowledge is Power; Absolute Knowledge is Absolutely Shocking!
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Certified 18650 Cell Reclamation Technician
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#3
hmm you look like you need cell overs hint hint wink wink...

hbpowerwall likes this post
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#4
(08-10-2018, 10:44 PM)Korishan Wrote: Nice setup. Kewl idea using the cooler  Wink

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.
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#5
(08-11-2018, 01:22 AM)Geek Wrote:
(08-10-2018, 10:44 PM)Korishan Wrote: Nice setup. Kewl idea using the cooler  Wink

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.
Korishan likes this post
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#6
Very nice build. Clean. I like the 3d printed parts also. Looks very professional. Its nice when something works as planned Smile . I don't get that very often lol.
Ibiza likes this post
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#7
@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)
Laptop battery pack processed (so far): 42 / batteries harvested: 291 / Usable batteries: 180  (62 %)

Cells tested: 291 (Average: 1835 mAh) / Cells in production: 0 (00 %)

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