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Hi all,
Been working on some upgrades to the dev kit for a bit, the draft documentation is out---rough around the edges but all the files are there for fabrication. The cell can now close with a simple C-clamp which is much more ergonomic and resistant to leaks. Most of the parts are forward-compatible.
Time-stamping the electrolyte formulation for Zn-I, I am making the documentation to build the dev kit chemistry agnostic (so I am taking these weights out of the docs for now)
zinc chloride - 1.36 grams
potassium iodide - 3.32 grams
ammonium chloride - 1.07 grams
deionized water - 8.50 grams
triethylene glycol - 0.55 grams
This usually ends up preparing around 11 mL of solution which we split evenly between the two reservoirs.
welcome @martinr and @jpengineering ! Iron hybrid RFBs are very appealing but managing hydrogen evolution is the real challenge---we've been working on some promising approaches here, Daniel has done some tests on a non-conventional iron electrolyte here: https://fbrc.nodebb.com/topic/44/only-fe-system.
I haven't seen Nighthawk's carbon felt video, but @rowow came through the forum already talking about his membranes! I'd like to get my hands on some to try (don't have the time right now to go into DIY membranes---we are using porous separators for the moment since they don't give us issues and we are mostly focused on cell/electrolyte R&D).
There is a now a Windows build, and fewer crashes related to file picker UI on Linux.
Downloads and source here: https://codeberg.org/FBRC/mystat/releases/tag/v1.2.2
from this paper, seems like nanomaterial synthesis needed: https://www.nature.com/articles/s41560-026-02091-w#Sec25
also they use triflate salts --- that's likely more expensive than the Zn (and, fluorine-containing, with all that entails)
Welcome @stevenhickey , great to have someone with as much experience as yourself here! I doubt you remember me but I think we crossed paths at IFBF in Brussels when I was doing my PhD a few years ago. I was/still am a big fan of Redflow systems, I think a lot of us were sorry to see the news about Redflow a while ago.
Great to hear that you've set up a home lab and are still pushing! Are you focused mostly on Zn-Br still?
Welcome @oliver.schlueter and @nadia_avva ! We are definitely indeed all about the ownership of energy and energy technologies here 
you are in the right place! We'd love to connect our batteries to a small wind turbine (Piggott-style, probably) as soon as they are large enough... your and Oliver/OSE's wind experience could be very helpful!
Made a longer-form video explaining our open-source battery project and diving into the details of the kit and chemistries we're working with!
It would really help our project out a lot if you could share this with interested folks.
YouTube link (feed the algorithm): https://www.youtube.com/watch?v=xhWBX1eLDr8
And of course, PeerTube: https://spectra.video/w/4wTobcS16Ww5UAZVMWrC9E
Please let me know what you think, comments, criticisms, suggestions---first time I've made a video like this and I have a lot to learn.
Made some Linux AppImages of improved MYSTAT software for anyone who uses it! Also runs on Windows ofc, it's just Python.
Filmed myself building a cell so you can see the whole process start-to-finish! Still working on updating the documentation for the clampable-cell branch. It works pretty darn well without any bolts.
Doing some tests now on this to get my wet lab back in action, here are the conditions and results so far on my blog
Also, this reminds me of the OpenAFPM project - they also use FreeCAD and provide a dashboard for people to input custom parameters for a small wind turbine generator, there is some FEM, and then design files are output. There is a video demo here: https://www.openafpm.net/cad-visualization
I know a few of the folks behind that project, I'm sure they'd be happy to give input on how to accomplish a similar goal but for flow batteries.
@muntasirms Muntasir, this is awesome! Sorry for the delay in getting back to you, I've just watched your walkthrough video today. The webapp loads for me but the viewport is empty? At least on a few different browsers it seems.
I watched the walkthrough though, very nice work! It looks very clean, would be awesome actually to have a 3D interface like this on the FBRC homepage, to make it a bit cooler like the https://www.open-quantum.org project.
It would be great to share the code as open-source as well, I am not familiar with the build123d library and would like to see how you've done it.
I have also been working on some automated exports from FreeCAD, to enable some CI/CD on our documentation, but nothing web-facing: https://codeberg.org/FBRC/RFB-dev-kit/src/branch/clampable-cell/CAD/FreeCAD/FreeCAD-exports.py
@muntasirms said in Build-a-Batt - A fully parameterized flow cell stack model:
That makes boundary condition declaration and the like much easier to automate as well - so I'm in the process of slotting this into an automated hydraulics/electrochemical simulation suite. Imagine generating your custom model and simulating a "digital twin" for estimates of performance prior to purchasing materials or finalizing design.
The FreeCAD models are also fully parameterizable, and can at least automatically update in the CfdOf workbench, but the whole thing in Python would be easier to handle for hardcore simulation, with any echem phenomena. This would be really cool, I would love to see you tackle some simulation/flow frame optimization! I have my hands full currently so I'm not sure when I'd get around to it.
Screenshot of the flow-frame file showing the OpenFoam CFD setup.
FYI, we still haven't actually done cycling experiments with the "large-format" 175 cm2 cell, so the design is mostly likely going to change somewhat!
I am not sure the small cell (18 cm2) design you show would seal also - we did a lot of testing with that sort of approach early on and it was hard to print the chemical resistant barbed fittings and endplates in one piece, which is why we separated it out in the dev kit.
@muntasirms said in Build-a-Batt - A fully parameterized flow cell stack model:
or a "fat stack" (3500cm^2) with extra, thicker bolts
I love it! I really hope we can get here one day 
we will certainly need all hands on deck to do so.
@muntasirms said in Build-a-Batt - A fully parameterized flow cell stack model:
I'm very open to constructive criticism on any part of the project (from ideation to UX to engineering). Have fun fiddling with it and let me know what you think!
Really happy that you've kicked this off, it shows whats possible in this space. Right now, I will be sticking to FreeCAD for prototyping and derisking - I'm much faster in a graphical CAD environment implementing design changes than in a code-based CAD approach. But I think the two are complementary - especially for simulation and customization.
There was actually a project that allowed for in-browser editing of FreeCAD files in a way sort of similar to your web app - a startup called Ondsel (now out of business) that made some contributions to FreeCAD source. They had a cloud tool called Lens that allowed you to build this sort of webapp directly from the FreeCAD file by exposing certain parameters. When they shut down they gave everything to FreeCAD, it looks like the Lens project is still going and you can host it yourself: https://freecad.github.io/lens-docs/
This might be a way to combine your customization approach directly with the FreeCAD source files? I would be a fan of this approach if we could link everything as closely as possible.
For UX: would be great to have a dropdown or similar to select templates for different standard configs, like the small cell/FBRC large-format/fat stack, etc.
This video seems to be AI generated and doesn't have that much real information? I have seen Ca-ion systems from (I think) a German group that looked good, but had a lot of organic synthetic steps if I remember correctly.
@rowow said in Using cnc router cut PVC foam boards as cell frame:
The long term goal and my personal next goal is to get into injection molding which of course is the best option.
At scale, definitely!
@rowow said in Using cnc router cut PVC foam boards as cell frame:
Ill see about uploading the cell fusion 360 model
A .step file would also be great so I could look at it in FreeCAD! I don't have a Fusion 360 license. I'd be curious to see if we could take a similar approach.
Nice find! Peter Allen has been at it for a while. I'd read his previous papers but not this one. A quick scan shows they are using an ion-exchange membrane, which @danielfp248 and I try to avoid if we can, since they are often the weak point of systems that rely on them.
Crossover of the mediators through the membrane will degrade performance. The possibility of this unwanted feature was examined by cyclic voltammetry on an electrochemical cell divided by the Fumasep FAS-50 anion exchange membrane in the 2 M KCl 20 % (v/v) EG AIB 3.0 electrolyte. The initial concentrations were 10 mM MV2+ in the left chamber and 10 mM ABTS2- in the right. A constant potential of 1.25 V was applied across the cell with 6.25 cm2 graphite electrodes for 24 h. This simulates the AIB 3.0 conditions. After the 24 h period CV was performed on catholyte to evaluate MV crossover and vice versa. We found no crossover through the membrane by the cyclic Voltammetry experiments.
I like how everything is commercially available at scale. There are quite a few organic flow battery startups that have tried to use methyl viologen as well like they do in this paper. I am curious what @danielfp248 thinks
