Flow Battery Research Collective

Hi, Christian here form Germany, Lower Saxony. I'm a senior software developer and like to play around with electronics, MCUs, ESPs, FreeCAD, 3D printing, milling, and anything else what you can DIY. I'm looking for some ideas to pimp up the energy storage capabilities of my PV setup since 1yr. There are so many ideas including compressed air storage, flywheels, thermal storage, and of course batteries / fuel cells. So I'm reading and viewing tons of research papers and DIY videos regarding this. As some others here, I found the reference to this project on heise.de.

I plan to start with the 3D printing soon. Thanks a lot for all the updates of all of your progress on building the kit. Once I'm ready to start I will also share my experiences during the build and hopefully test process.

Hi Guys,

as promised I also want to document my journey on building the kit. Yesterday I started with the very simple endplates:
The right one was the first, printed with 15% infill, the left one with 60%, but still just 2 wall loops. Of course, you can feel the difference in the weight.

One problem I noticed was, that I had a PEI textured print plate only. Therefore the surfarce looks fine, but it might not be the best to seal the chamber.

To solve this I ordered a flat "high temp" plate from Amazon, which arrived today. Of course, next print cycle was in the queue. This time with 5 wall loops:

On the right the initial version, on the left the new one. You can see the difference immediately. Well, the picture still gives the impression that it is not flat, but it is:

This is how the old one was looking:

BTW, I printed all of them in Geeetech PLTG on a Bmboo Lab P1S with AMS. The printing time for version with 15% infill was arround 25min, 48min for the version with 60%. Printed with 0.2mm layer height.

Looking forward to print my first parts in PP in the next days...

End of last week I had my very first tries in PP printing. I used the same flat plate I used for the endplates. While looking quite good at the beginning, the part started to high warpings and got loose from the plate. Then the filament seems to be so "soft" that I got a jam close to the extruder and once in the Bambu AMS. In both cases I had to partly disable them to get the jam resolved.

At least I managed one instance by using the packing tape method:


I decided to use only one stripe in the middle as I noticed a gap / overlap when using two side by side. Perhaps I should have used two additional ones on top / bottom to avoid the warping of the bim. At least with this tape I had no problem to lose the part from the surface.

While the result was looking promising, it has a big problem. It is leaky. I made a simple blow test while closing the outlet with my fingers. Still I could hear the air flow through the layers. Before going on with the PP printing of other parts, I will repeat the print while adjusting the infill pattern, layer height and flow parameter until the blow test is satisfying. I also have 2 other PP filaments to test and a special plate promissing to great for PP printing - let's see.

@quinnale said in Towards a working system:

I cheated and moved the cell the lab I work in for leak testing while I seek time to explore pumps. My PLA flow frames leaked, moving on from that.

Your cell looks quiet good. Damned that it is leaking. I guess this is the most critical test what we are all afraid of. But it has to be done, otherwise we will have the chaos later on. Good luck with your PP prints, it is really a "fun" ...

I've also been using imperial hardware (1/4-20 bolts), which the holes are slightly undersized for. Not big issues, just consequences of my choices.

One option is to use the FreeCAD source and adjust the diameters accordingly.

@sepi Good idea, I was also thinking to use a ESP32 with micropython - makes prototyping much easier and if you like you can easily add a simple web UI.

Printing the larger parts gives the impression that I'm almost done, but there is still a lot work to do...

I'm still waiting for the silicone foil, should arrive next week. BTW, has anyone tried to "mill" the silicone foil and graphite foil? I'm thinking to put it below a 2-3mm wood plate and use my OpenBuilds CNC router for it, wither with an engraving tool or a 4mm endmill...

@kirk In general this is exactly the way how all of us should act here (and in all other open source projects). But it is always better to have something like this in advance and it does not harm. I highly welcome to have a written code of conduct. Thanks Kirk, for taking care.

@sepi thanks for the warm welcome and hope you are running well with your build - which is already looking very good

@kirk, @sepi
yeah you are right, it is not so important for the outer endplates. But I used them as a POC to see how much I can get out of the 3d print.

@sepi Great job, your assembly is really looking quite good. Can't wait to see how it will perform.

@danielfp248 Thanks for the tips. Yesterday I made some new tests and now I have one which seems to be close. When doing my blow test I was able to seal the outlet with my finger, so that I did not hear / feel any air escaping any more.

With the three pieces of tape put side by side the brim also stick very good to the tape, I have not seen any warping. I also used the ironing so that the top surface also feels much more flat now. Just the filament is getting me crazy. After one print I always have a bigger piece at the end of the extruder, so that it will not support for the next prints.

@sepi I'm also using tasa packing tape, but without any glue:

I'm printing with "Formfutura Centaur PP" filament. Once I lifted the corner of the brim I had no issues to pull the print from the tape.
This is how I did my blow tests:

When I just blow into the "nozzle" I can hear the sound of the escaping air. While gently pressing the small finger against the outlet I noticed the change in the sound as the air was escaping somewhere else.

Yesterday I made a new test with the BASF Ultrafuse PP filament - and it behaves totally different. When keeping all the parameters as before, it was loosen from the tape after some layers. I also noticed massive warping, the brims were also warped up.

Next I used the print profile from BASF. It uses a much higher temperature (which is not in line with the datasheet), but the result was the same. In addition, the packing tape melted so I had to remove it.

Next I used a this film of MAGIGOO PP adhesive glue, which gives a good result:

It has some stringing (might be because of the high temp) but fastened to the printing plate quiet well. Removal after cooling down was also easy. Unfortunately, the flow was too much so that the hole in the port was solid. I need to tune the parameters further or to use the new update from @kirk where the inner diameter is increased from 2 to 3mm.

@sepi @danielfp248

You can pretty easily get them on digikey or similar

yeah, I usually order at RS; there will by some way to get them.

What's your equipment and experience with soldering?

I'm using an ERSA i-CON and Weller 1010 since "some" years. Soldering of small footprints will be done by soldering below a Bresser 3D Microscope. I do not have a reflow oven, so the BGA will be a challenge but should be possible with my hot-air soldering station as well.

When you solder this by hand some pieces have really short contact points, so it is very hard to figure our where you have shorts.

You are absolutely right you have to be very careful. But I also manged to turn the 0-ohm resistor on the ESP32-cam to use the external antenna.