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AJW22's modular 3d printed 40kWh PowerShelf
#31
(06-10-2019, 09:46 AM)ajw22 Wrote:
(06-10-2019, 08:51 AM)simonisabella Wrote: 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 not read 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,
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#32
(06-10-2019, 10:49 AM)simonisabella Wrote:
(06-10-2019, 09:46 AM)ajw22 Wrote:
(06-10-2019, 08:51 AM)simonisabella Wrote: 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 not read 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!
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Modular PowerShelf using 3D printed packs.  40kWh and growing.
https://secondlifestorage.com/showthread.php?tid=6458
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#33
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 pack when I slide the packs on my shelf during maintenance.

new design with stoppers


previous design
Modular PowerShelf using 3D printed packs.  40kWh and growing.
https://secondlifestorage.com/showthread.php?tid=6458
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#34
(02-27-2019, 01:23 PM)ajw22 Wrote: A few words on Raspberry Pi 3 + Grafana monitoring, and its uses.

I thought about using rePackr to assemble the packs for my first 14s92p battery.  Turns out I'm too lazy to catalogue 1288 cells, much less sort/fetch the exact ones 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 totally random cells, though I capacity & leak tested all of them.

After 6 months of operation, I finally got around to installing a remote monitoring system using Raspberry 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), some had cells with electrolyte leaks, others were low/high capacity purely due to bad luck.

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


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


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 any capacity balance issues 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?
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#35
Absolutely not a stupid question.
The chinese "Smart BMS" comes with a bluetooth dongle.  The (extremely poorly written) specifications are listed on their website https://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 and query 3 BMSs and once a minute upload 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.
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Modular PowerShelf using 3D printed packs.  40kWh and growing.
https://secondlifestorage.com/showthread.php?tid=6458
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#36
First of all, congratulations.

I'm new to the forum, my English is not good. I couldn't find the 3d files.
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#37
(07-22-2019, 09:24 AM)sanik46 Wrote: First of all, congratulations.

I'm new to the forum, my English is not good. I couldn't find the 3d files.


hm... strange... attached the .scad file to the first post (again?).
Modular PowerShelf using 3D printed packs.  40kWh and growing.
https://secondlifestorage.com/showthread.php?tid=6458
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#38
(07-03-2019, 03:36 PM)ajw22 Wrote: 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 pack when 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.
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#39
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!
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#40
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.
Modular PowerShelf using 3D printed packs.  40kWh and growing.
https://secondlifestorage.com/showthread.php?tid=6458
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