AJW22's modular 3d printed 60kWh PowerShelf

ajw22 said:
Another quick update:

* Noticed a few days agothat Battery#2_Pack#11 wasconsistently ca0.05V lower. Log indicates this drift started about 2 weeks ago, getting worse every day => there's aleak! Visual inspection found only 1 obvious candidate, which I replaced. Took all in all about5 min.
I thought about boosting the pack up to the same voltage as the other packs, but decided to see how the 50mA balancer would deal with this.
At 3.8V, itwas leaking at a rate ofabout 30mA. A more powerful balancerwould have hidden this problem?

image_xeckny.jpg


* Built the firstrack, anchored to the concrete floor and wall.Moved battery#2 (14S104P) into rack today.

* Still under constructionbattery#3 nowhas all its cells. Fused pack#1, 13 more to go! Before anyone comments about the cold solder joints: it's a very localized quick high temperature solderingandit's rock solid.
This latest design iteration uses just one long 5.5mm^2 wire as the busbar. Plenty for my max 30A use. Removing the insulation is a 1step process, and no more twisting orsplicing. And it's well secured to the pack, no chance of accidentally ripping out fuses by pulling too hard on the connector.


just amazing stuff mate! LOVE the design and thrilled to be able to utilize it (thanks so much for sharing)

first print has lots of bridging. have removed them from half of the battery holders as in the pic and working on the other half now.

image_axpnqj.jpg


Cant wait to get the printing sussed so i can continue to produce these units.
 
Those 3d printers with long bowden tubes (the white nylon tube) like to continue extruding even when the extruder gear stops. Try using my Slic3r settings. Some of the methods I used to reduce this effect: decelerate extrusion before stopping; retract filament 6mm before travel, etc.

Make sure your 18650 cells fit. If your filament extrusion amount is too high, the walls become too thick and the cells might not fit.
 
ajw22 said:
Those 3d printers with long bowden tubes (the white nylon tube) like to continue extruding even when the extruder gear stops. Try using my Slic3r settings. Some of the methods I used to reduce this effect: decelerate extrusion before stopping; retract filament 6mm before travel, etc.

Make sure your 18650 cells fit. If your filament extrusion amount is too high, the walls become too thick and the cells might not fit.

will try your slic3r settings tomorrow morningfirst thing. cells fit beautifully!
 
Maniac_Powerwall said:
What kind of breakers do you use for DC?


I use "2 pole DIN breakers" (common part,google it) rated for 440V DC and25A, 32A and63A.
If anyone is considering using these, make sure they're rated for DC current!

Oh, and these things are not failure proof. Over the years, I've come across 3 failed 2 pole breakers. 2 made by a reputable Japanese company. All of them failed with no externally visible damage, and just one pole in the always-open position.
 
ajw22 said:
Maniac_Powerwall said:
What kind of breakers do you use for DC?


I use "2 pole DIN breakers" (common part,google it) rated for 440V DC and25A, 32A and63A.
If anyone is considering using these, make sure they're rated for DC current!

Oh, and these things are not failure proof. Over the years, I've come across 3 failed 2 pole breakers. 2 made by a reputable Japanese company. All of them failed with no externally visible damage, and just one pole in the always-open position.

What brands? So not the only the broken ones. Maybe better the working :)
 
Maniac_Powerwall said:
ajw22 said:
Maniac_Powerwall said:
What kind of breakers do you use for DC?


I use "2 pole DIN breakers" (common part,google it) rated for 440V DC and25A, 32A and63A.
If anyone is considering using these, make sure they're rated for DC current!

Oh, and these things are not failure proof. Over the years, I've come across 3 failed 2 pole breakers. 2 made by a reputable Japanese company. All of them failed with no externally visible damage, and just one pole in the always-open position.

What brands? So not the only the broken ones. Maybe better the working :)


For this project I used all cheapo Chinese items from AliExpress. Note that I use them mostly for the convenience of quickly and safelydisconnecting items, and only secondly as a last line ofdefense reovercurrent protection. The chargers/BMS have their internal current limits set (1st to trip), have a fuse (2nd to trip), and only then the breakers come into play.


Breakers:
TOMZN 2P xxA DC 440V Circuit breaker MCB C curve
Note that you MUST NOT REVERSE POLARITY, ie. (+) to left pole, (-) to the right. Wrong connection might result in fire.
!!! Just realized that they are not suitable when the current can flow in the opposite direction, ie. supply at bottom and load at the top.!!!It's probably ok in this case since max 60VDC is applied, but looking for a non-polarized replacement nonetheless
Another thing to keep in mind is that these do not necessarily trip immediately. A 32A breakerrunning64A will trip only after anytime between8sec ~ 2min. At 38A, it's anytime between 5min and eternity!
https://www.aliexpress.com/item/2P-32A-DC-440V-Circuit-breaker-MCB-C-curve/32786133199.html?spm=a2g0s.9042311.0.0.27424c4djOvgQN

Busbar:
Neat and convenient, but only 63A. That's all flowingcurrentcombined, not per port. Gets uncomfortably warm at that current. I'm using only 30A now, but will eventually replace this with a higher current one.
https://www.aliexpress.com/item/Cop...258.html?spm=a2g0s.9042311.0.0.27424c4djOvgQN
Box:
I removed all tabs at the bottom&top to provide better cooling for the breakers and busbar.
https://www.aliexpress.com/item/9-12-ways-Plastic-distribution-box-for-circuit-breaker-indoor-on-the-wall/2045423579.html


image_xzofkv.jpg
 
is there a scad file for your latest 8 pack, as i need to modify the amount in parallel to suit my ender 3 bed size -230 x 230
 
simonisabella said:
is there a scad file for your latest 8 pack, as i need to modify the amount in parallel to suit my ender 3 bed size -230 x 230

I attached "BatteryPack8.stl.zip"to the post on page#2 with all the other files"BatteryPack9.zip" on my first post. You can change the pack size by changing "cells_x=14;cells_y=8;" towards the bottom of the file.
 
ajw22 said:
simonisabella said:
is there a scad file for your latest 8 pack, as i need to modify the amount in parallel to suit my ender 3 bed size -230 x 230

I attached "BatteryPack8.stl.zip"to the post on page#2 with all the other files. You can change the pack size by changing "cells_x=14;cells_y=8;" towards the bottom of the file.

how do you get open scad to read a stl file, as once i open a batterypack 8 stl, it goes directly to cura, if i open open scad it will notread the stl file, it needs to be in open cad format. your original post on the 1st page has a scad file attached, but that is different to the design you are using now, do you have a open scad file for the design you are using now,
 
simonisabella said:
ajw22 said:
simonisabella said:
is there a scad file for your latest 8 pack, as i need to modify the amount in parallel to suit my ender 3 bed size -230 x 230

I attached "BatteryPack8.stl.zip"to the post on page#2 with all the other files. You can change the pack size by changing "cells_x=14;cells_y=8;" towards the bottom of the file.

how do you get open scad to read a stl file, as once i open a batterypack 8 stl, it goes directly to cura, if i open open scad it will notread the stl file, it needs to be in open cad format. your original post on the 1st page has a scad file attached, but that is different to the design you are using now, do you have a open scad file for the design you are using now,

Stupid me uploaded the same .stil again when I meant to upload the .scad. Fixed!
 
If anyone is still planning to use my pack design:
I've attached the latest source .SCAD file to my first post as "BatteryPack9.zip".
Latest improvement adds 8 small stoppers to prevent my white brackets from moving along the packwhen I slide the packs on my shelf during maintenance.

new design with stoppers

image_kporqq.jpg


previousdesign

image_skorxo.jpg
 
ajw22 said:
A few words on Raspberry Pi 3 + Grafana monitoring, and its uses.

I thought about using rePackr to assemble thepacks for my first 14s92p battery. Turns out I'm too lazy to catalogue1288 cells, much less sort/fetch the exactones rePackr says I need. So instead I went the sort-into-100mAh-buckets route.
For the second battery(14s108p) I couldn't be bothered to do even that. The third battery(another 14s108p) was assembled using totallyrandom cells, though I capacity & leak tested all of them.

After 6 months of operation, I finally got around to installing a remote monitoring system usingRaspberry Pi 3 + Grafana. The first time I drained to 3.2~3.35V, it was immediately noticeable that the packs had mismatched capacities. One pack had broken fuses (bad soldering), somehad cells withelectrolyte leaks, others were low/high capacity purely due to badluck.

(ignore the noises/blips. Just software glitches I've nowmostly sorted out)

image_rojpdt.jpg


After fixing the problems as well as shuffling some low/highcapacity cells to balance out the capacities:

image_ydygej.jpg


So not only does this system help me identify and fix issues, it also allows me to build my packs in the most lazy way and sort out anycapacity balanceissues later :)

Maybe a stupid question, but what is the source of your data that you gather. Is it supplied by your solar chargers? Or do you have additional hardware (BMS) you use for this?
 
Absolutely not a stupid question.
The chinese "Smart BMS" comes with a bluetooth dongle. The (extremely poorly written)specificationsare listed on their websitehttps://www.lithiumbatterypcb.com/, and there are several projects on the internet if you search for "smart bms bluetooth programming". I couldn't get any of them to run properly, so I wrote my own python script to connect to andquery 3 BMSs and once a minuteupload the data to a local (RaspPi3 that is) Postgres DB server. Really still a work in progress, but at least it has stopped crashing all the time.

I'll add this to my previous post.
 
First of all, congratulations.

I'm new to the forum, my English is not good. I couldn't find the 3d files.
 
ajw22 said:
If anyone is still planning to use my pack design:
I've attached the latest source .SCAD file to my first post as "BatteryPack9.zip".
Latest improvement adds 8 small stoppers to prevent my white brackets from moving along the packwhen I slide the packs on my shelf during maintenance.


yes I have used your design as a startng point for my own STL design which i will upload some pics shortly. The speed of the print is an important thing but I have edited my design for high speed serviceability using sprung connections from nickle strips rather than soldered connections.

Thanks so much for open sourcing your design I hope to show my work shortly.
 
I Like the very clean and pure look.
Very nice build!

Are you using fuse wire (if yes which one?) on the positiv side of your cells?
I ask because of parallel using fuse wire is a bit confusing to me. Isnt the amperage to high?

Thanks!
 
My "fuse wire": I dissect an AWG22 stranded tin coated copper wire, which yields 17x individual strands of AWG34 (or slightly thinner). I think it broke at somewhere between 5A~7A.
Same wire on both pos and neg sides.

An interesting aspect of my cell fusing is that due to the length (x2 for both sides) it adds perhaps 30mOhm of resistance, and the resistance goes up with temperature. That alone limits the current a cell can (ab)use. Not sure if it's a good thing or bad thing, but it's been working fine so far, and has activated successfully on several faulty cells.

My pack is limited to just 30A (through charger/inverter settings, as well as by a breaker, fuse and BMS), and max current under normal use is about 25A. This unusually low current rating is crucial in allowing me to make certain design decisions that would otherwise cause problems.
So each cell dis-/charges at max 0.25A. Even doubled up it's just 0.5A, no problem for the fuse wire.
 
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