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Oliman's 18650 Power Wall
#1
Hi All,

I got excited about building a PowerWall about a year ago now.
I stumbled across some crazy Australian guy on youtube (hbpowerwall  just in case there was any question) who was using laptop batteries to power his house and I was immediately intrigued. 

Just to give a little additional context, I had just recently finished lining my entire roof with solar panels and learned (during that Christmas) that when it snowed and brought down the power lines, I couldn't actually use any of my solar because it was grid tied and required the grid to be active before I could actually use the power that was coming from my solar. 

Upon further investigation, it seemed the only way to remedy this travesty (which my solar installer conveniently neglected to inform me) was to add battery backup to my system. However, everything I looked at, that was commercially available, was either super tiny or just plain unavailable (I'm looking at you Tesla PowerWall).

Well, after binge watching everything I could find on DIY PowerWalls (for a few weekends). I finally deemed myself "expert enough" to try and tackle my own project.

I decided on 14S 100P, mainly because 100 seemed like a much rounder number than 80 (yes - that was literally the only reason).

I started out by buying a ton of chargers and batteries and then completely destroying my exercise room with broken plastic and boxes filled with BMS boards.





Then I started soldering the packs together. I fused both the positive and negative sides of the packs with Fast Glass Axial Fuses (which I picked up from 18650ed on eBay that guy is awesome).

Everything seemed to be going pretty smoothly until I touched 2 packs together (in the way two packs should never touch) and spot welded their bus bars together, immediately blowing ~300+ fuses. This was definitely a problem... I needed a way to make the packs safer. 

At that point, I decided it would be a great idea to just 3D print covers for my packs. How hard could that be? I mean, the batrium system I had pre-purchased had a 3D printed cover printed for it. The Batrium cover even had two colors. How cool would it be to have custom battery covers with multiple colors? Maybe even put my name or something on them. The possibilities seemed endless, and it was at that exact moment that I had somehow convinced myself that even though I was no where near completion of my PowerWall, that I NEEDED to pause everything and learn how to model/design and 3D print custom battery covers.

Fast forward a couple more months and I had finally worked out how to dial in/print and design some rudimentary STL files for my custom battery covers. There was only one problem. Remember that 100P decision I arbitrarily made before? Well now it was time for that to bite me because I had to print my covers in 2 parts and there was a seam in the middle when I put them on a battery pack. This was just unacceptable. I had come too far to compromise at this point, so I went in search for a larger 3D printer. The only problem was, any 3D printer I found that was > 650mm was in the ballpark of $20,000.

So I gave up...
Well, let me put that a better way. I should have given up, but what I actually did was decide to build my own 3D printer. I mean, how hard could it be? I build computers for fun.

Turns out, it's not actually that hard. But I did waste another couple more months sourcing parts and figuring out wiring and frying a couple 3D printer boards, but I finally had something that was large enough to print my battery covers.

It wasn't super sexy, but it was definitely functional enough for what I needed.  




That pretty much brings the project up to date for today.
I looked, but I don't actually have any pictures of the battery covers. I'll take a picture tonight to share.

For now, I'll leave one more update of the charging station finally moving to the garage.

Redpacket likes this post
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#2
Adding some pictures of the battery covers.

some half done Battery packs with covers:
 

Naked pack:
 

Battery Covers:
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#3
Nice setup.
Would you mind sharing your Stl file ?
beserker786 likes this post
Batteries harvested: 802 / Usable batteries: 747 (93 %)

Cells tested: 747 (Average: 1878 mAh) / Cells in production: 0 (00 %)

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#4
(04-24-2019, 12:04 AM)Sholphin02 Wrote: Nice setup.
Would you mind sharing your Stl file ?

I don't mind sharing the stl files, but they are pretty specific to my needs and while initially built to be generic/expandable that pretty much got thrown out the window around iteration 28 or so. I'll try and figure out how to add an *.stl to thingiverse, never shared stl files publicly but that seems to be a pretty popular solution.

Couple of other thoughts...
I can't imagine anyone else wanting Oliman etched into their packs
It didn't look great slicing up the 100P configuration to print on smaller printer beds, although it's totally doable

Also, I'm still very much iterating on the design.
For example, I was playing around with the idea of adding a hole for 3/8" bolt + "nut trap" for a cheap/easy metal threaded model to secure the sides together. Bonus of this design is you could bolt multiple packs together to expand a 14s 100p say into a 14s 200p and still have logical "battery modules" instead of a mess of connected packs stacked on top of eachother. 



Another thought, along the same line of thinking. If I had a super sturdy bolt going through my pack, I could probably design some locking rails that the bolts slide into. Either for mounting or just for safety/stability of not being able to fall off a shelf. I could probably even come up with a ceiling mount... powerwall power-ceiling anyone?

Anyways, I actually just stopped by to share a small update and got sidetracked talking about the battery covers.
Finally got all my laptop batteries through capacity testing... keeping 1800mah+ 
I was only going to keep 2000+ but I have read the Opus chargers can be up to 200mah off so I dipped down a bit.
Now I just need to wait a couple weeks test for discharges.

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#5
I finally got around to uploading my battery covers to thingiverse.
Maybe they will be of use to someone else.
cowpen likes this post
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