<?xml version="1.0" encoding="UTF-8"?><rss xmlns:dc="http://purl.org/dc/elements/1.1/" xmlns:content="http://purl.org/rss/1.0/modules/content/" xmlns:atom="http://www.w3.org/2005/Atom" version="2.0"><channel><title><![CDATA[Popular Topics]]></title><description><![CDATA[A list of topics that are sorted by post count]]></description><link>https://fbrc.nodebb.com/popular/alltime</link><generator>RSS for Node</generator><lastBuildDate>Mon, 18 May 2026 09:25:25 GMT</lastBuildDate><atom:link href="https://fbrc.nodebb.com/popular/alltime.rss" rel="self" type="application/rss+xml"/><pubDate>Thu, 06 Feb 2025 03:49:50 GMT</pubDate><ttl>60</ttl><item><title><![CDATA[Designing the large-format cell]]></title><description><![CDATA[Did another leak test today with water, correctly with 2x ~12 mm plywood endplates each side. Saw no leaks through the edges which was great news, but the barbed connections on the cell showed signs. Also, the MP-6R pumps struggle with the current flow frame design, which has 0.8 mm wall thickness and a 1 mm internal channel (electrode area therefore 2x0.8 + 1 = 2.6 mm thick). I remade (and pushed to the repo) the flow frame with a 3 mm internal thickness, in order to alleviate this pressure drop.
Here is the test setup, I ran out of tubing (ordered 2m but they sent 1 m  ), so the connections aren't ideal but this time no kinks in the flow path. Note, I put these drain valves in, of course they are pointing the wrong way for now, will need to elevate the setup so they can point down in the future.
[image: 1769764493660-9fafda86-7f70-439f-9ecb-eeb9a7316215-img_20260129_153901-resized.jpg]
Because all the connections are on one side (in anticipation of stacking these cells), I also made "front" and "rear" versions of endplates, inner/outer current collectors, and gaskets in the FreeCAD files. This will make low-volume prototyping a bit more expensive but more robust against leaks, which no one wants!
[image: 1769763690358-037a7741-97dc-4012-8e95-cf8ab8760653-image.png]
This is the dimension that went from 1 mm to 3 mm to facilitate using MP-6R pumps.
[image: 1769763764115-d4ac6efb-4694-4d13-a941-8ffb85995001-image.png]
We have the MP-6R now. It is the 6W high-flow version. the MP-10 is also 6W but lower flow / 50 % higher max pressure, then the MP-15R can do almost 3x higher pressure than the MP-6R but at 10 W.
@danielfp248 can hopefully print the 3mm flow frames and I can get them at FOSDEM, then try them out. If it turns out we need the bigger pumps, I'll order them from AliExpress:
[image: 1769763852108-f14b9379-cbc5-4542-940c-b33c0bacdb14-image.png]
]]></description><link>https://fbrc.nodebb.com/topic/11/designing-the-large-format-cell</link><guid isPermaLink="true">https://fbrc.nodebb.com/topic/11/designing-the-large-format-cell</guid><dc:creator><![CDATA[kirk]]></dc:creator><pubDate>Thu, 06 Feb 2025 03:49:50 GMT</pubDate></item><item><title><![CDATA[Following your documentation – feedback &amp; questions]]></title><description><![CDATA[@danielfp248  I always performed more cycles before starting 40 mA / 100 mAh charging (10 half-cycles at 20 mA / 10 mAh + 4–10 half-cycles at 30 mA / 10 mAh). The cell was also wet with demineralized water (leakage test). Could this also be the cause? I was also always using the membrane frame. Wouldn't the electrolyte leak through the paper membrane?
@kirk  Apart from solving the electrolyte leakage issue, does this "pulling-through configuration" improve the total capacity of the system in any other way? Also, I am wondering whether you are using the default flow frame from the documentation (2 mm thick, right?) or a different one with another thickness and the 0.1 mm silicone gaskets.
]]></description><link>https://fbrc.nodebb.com/topic/16/following-your-documentation-feedback-questions</link><guid isPermaLink="true">https://fbrc.nodebb.com/topic/16/following-your-documentation-feedback-questions</guid><dc:creator><![CDATA[gus]]></dc:creator><pubDate>Wed, 02 Apr 2025 07:03:45 GMT</pubDate></item><item><title><![CDATA[My build (very slowly progressing)]]></title><description><![CDATA[@sepi Without the four-wire control the pump speeds are definitely harder to manage, sorry to hear that, though the PWM regulator may help. Can you visually see how different the rotation speeds are? That should be rough proxy for volumetric flowrate. I am not surprised they won't spin below 11 V.
@sepi said in My build (very slowly progressing):

Is this 20-40ml/min measured with the cell in line or just the pump.

Ideally best to measure with the cell inline, to be closer to the actual conditions. However, as the tubing wears, this can drift, just FYI. Not a huge deal but something to be aware of.
@sepi said in My build (very slowly progressing):

Is the figure obtained with water or electrolyte?

Water for now, just as a proxy, minimize exposure to electrolyte. This is kind of a 1, maybe 2 significant digit measurement, no more (the volumetric flowrate).
@sepi said in My build (very slowly progressing):

What would you recommend doing against the excess flow?

@sepi said in My build (very slowly progressing):

the left passing up to 40% more water at the same voltage.

At the same voltage, is the left pump spinning at (nearly) the same rate as the right? if they are spinning at the same rotational speed and the left is passing 40% more water, it sounds like there is some flow restriction in the right pump's flow loop. If they have identical flow loops (in terms of pressure drop), and are set at the same voltage, I would guess that they should rotate at similar speeds, but this may not be the case for the brushed motors (e.g. variance in motor properties).
What is important for testing, is that both pumps are above a minimum flowrate to ensure good mass transfer, and that the pressure imbalance between the two sides isn't too great as to cause transfer of electrolyte from one side to another through the separator. If the flowrates aren't perfectly matched but those two previous conditions are met, it's not a big issue, although it's just better for repeatability for them to be the same.
]]></description><link>https://fbrc.nodebb.com/topic/30/my-build-very-slowly-progressing</link><guid isPermaLink="true">https://fbrc.nodebb.com/topic/30/my-build-very-slowly-progressing</guid><dc:creator><![CDATA[kirk]]></dc:creator><pubDate>Fri, 11 Jul 2025 07:33:28 GMT</pubDate></item><item><title><![CDATA[New member introduction thread!]]></title><description><![CDATA[Re: New member introduction thread!
Hi, I am vesko. Not very intuitive how to introduce myself, but I hope that by touching Al over the previous screen, this is the place. Anyway.
I am a retired electronic HW/SW engineer. Have all the time for my own projects. Independent living is my highest priority and I am ready and willing to put my time, money and efforts to achieve that goal and possibly help others along the way.
I bought a house in the boonies, I had a water well drilled. I am designing and implementing my oven silt filtration system that doesn’t need to buy and replace filters, chemicals etc. only if something breaks I need to repair/replace it. I installed solar system. Prefer water turbines, but it’s a much more complicated project, so solar is an imperfect but fast solution. Not very happy with the price of lithium batteries “lease” they call it purchase. It’s not a purchase / it’s a 10-15 years lease. So, looking forward to be battery independent
]]></description><link>https://fbrc.nodebb.com/topic/13/new-member-introduction-thread</link><guid isPermaLink="true">https://fbrc.nodebb.com/topic/13/new-member-introduction-thread</guid><dc:creator><![CDATA[vesko]]></dc:creator><pubDate>Thu, 13 Feb 2025 17:26:51 GMT</pubDate></item><item><title><![CDATA[Blog: czahl&#x27;s build]]></title><description><![CDATA[@czahl I am a huge fan of trying this, especially for the larger format where setups are likely to be more permanent. As kirk mentioned we have never actually tried it, so please let us know if you do!
]]></description><link>https://fbrc.nodebb.com/topic/34/blog-czahl-s-build</link><guid isPermaLink="true">https://fbrc.nodebb.com/topic/34/blog-czahl-s-build</guid><dc:creator><![CDATA[danielfp248]]></dc:creator><pubDate>Thu, 24 Jul 2025 20:11:22 GMT</pubDate></item><item><title><![CDATA[Alternative Electrolytes]]></title><description><![CDATA[@danielfp248 huh, that makes a lot of sense.
]]></description><link>https://fbrc.nodebb.com/topic/35/alternative-electrolytes</link><guid isPermaLink="true">https://fbrc.nodebb.com/topic/35/alternative-electrolytes</guid><dc:creator><![CDATA[sepi]]></dc:creator><pubDate>Sun, 27 Jul 2025 17:31:17 GMT</pubDate></item><item><title><![CDATA[How should we control the centrifugal pumps? TRIAC&#x2F;thyristor etc? Need help from controls&#x2F;electrical people]]></title><description><![CDATA[@kirk said in How should we control the centrifugal pumps? TRIAC/thyristor etc? Need help from controls/electrical people:

It seems to work! At least enough for testing purposes. Here is a video: https://spectra.video/w/8xipM8aXnBkDXnu4kkRpqT

Here is the code for this test: https://codeberg.org/FBRC/RFB-test-cell/src/commit/d10834bc7dd67736e708c9a33832a5602ab3ca28/firmware/FlowrateRampTest.ino
]]></description><link>https://fbrc.nodebb.com/topic/8/how-should-we-control-the-centrifugal-pumps-triac-thyristor-etc-need-help-from-controls-electrical-people</link><guid isPermaLink="true">https://fbrc.nodebb.com/topic/8/how-should-we-control-the-centrifugal-pumps-triac-thyristor-etc-need-help-from-controls-electrical-people</guid><dc:creator><![CDATA[kirk]]></dc:creator><pubDate>Tue, 04 Feb 2025 20:29:54 GMT</pubDate></item><item><title><![CDATA[Only Fe system]]></title><description><![CDATA[This test showed some deterioration on cycling:
[image: 1758097795042-c586de1d-8d24-4884-bd7a-a00afb789080-image.png]
I took out the catholyte and anolyte when charged (you can see the anolyte (left) and catholyte (right) in the pictures below). There isn't any hydroxide precipitation in either one. However there are some pieces of detached Fe metal on the anolyte, which I think are what causes the slight loss in capacity and increases in ohmic resistance as a function of time.
[image: 1758097834649-5ee56443-1754-4f62-9a96-83d6194304ca-image-resized.png]
]]></description><link>https://fbrc.nodebb.com/topic/44/only-fe-system</link><guid isPermaLink="true">https://fbrc.nodebb.com/topic/44/only-fe-system</guid><dc:creator><![CDATA[danielfp248]]></dc:creator><pubDate>Mon, 01 Sep 2025 14:20:30 GMT</pubDate></item><item><title><![CDATA[Sourcing parts]]></title><description><![CDATA[On it, thanks @sepi !
]]></description><link>https://fbrc.nodebb.com/topic/29/sourcing-parts</link><guid isPermaLink="true">https://fbrc.nodebb.com/topic/29/sourcing-parts</guid><dc:creator><![CDATA[kirk]]></dc:creator><pubDate>Sun, 29 Jun 2025 19:23:54 GMT</pubDate></item><item><title><![CDATA[Towards a working system]]></title><description><![CDATA[@muntasirms Absolutely! A bunch of other great documentation on here, wanted to try to my part.
I have a colleague who uses HIPS exclusively in strong alkaline systems. Significantly easier to print than PP from my limited experience.
It's not pure polystyrene (which is great for alkaline), but the additive(s) don't seem to affect their tolerance too much.
I'll keep you posted on compatibility as I test these systems! Not sure how long the parts will last yet.
]]></description><link>https://fbrc.nodebb.com/topic/23/towards-a-working-system</link><guid isPermaLink="true">https://fbrc.nodebb.com/topic/23/towards-a-working-system</guid><dc:creator><![CDATA[quinnale]]></dc:creator><pubDate>Thu, 05 Jun 2025 17:45:42 GMT</pubDate></item><item><title><![CDATA[Separator material]]></title><description><![CDATA[@danielfp248 ah, that makes sense as a last resort measure but would it not be nice to not lose charge? Well it all depends on how easiy it is to counteract by setting a different flow for the different electrolytes.
]]></description><link>https://fbrc.nodebb.com/topic/41/separator-material</link><guid isPermaLink="true">https://fbrc.nodebb.com/topic/41/separator-material</guid><dc:creator><![CDATA[sepi]]></dc:creator><pubDate>Wed, 20 Aug 2025 14:20:09 GMT</pubDate></item><item><title><![CDATA[Working on a large scale open source flow battery design and kit]]></title><description><![CDATA[I'm no expert ether. We used quick setting plaster a lot in construction for repairs on a lot of things and now they have a "wood epoxy" which is an epoxy for wood repairs. You have a thing epoxy you brush on onto wood which provides a good bonding surface for dry rotted wood and then you mix an epoxy that works more like the quick setting plaster and creates a strong enough repair that you can nail it. These plasters and epoxies could be formed or poured to create a nice mold. For the quickset we could build up an area, then carve and shape it before it fully set. The surface is very smooth and with a spray sealer of some kind should be even better for molds.
A quick look into casting, it looks like the most common is using silicon for making the mold. Yes it lets you do detail, but it is also soft and flexible. Not good for making thin plates without warpage.
]]></description><link>https://fbrc.nodebb.com/topic/9baae384-75b5-40bc-ae3c-de14abd8f8e4/working-on-a-large-scale-open-source-flow-battery-design-and-kit</link><guid isPermaLink="true">https://fbrc.nodebb.com/topic/9baae384-75b5-40bc-ae3c-de14abd8f8e4/working-on-a-large-scale-open-source-flow-battery-design-and-kit</guid><dc:creator><![CDATA[Vorg]]></dc:creator><pubDate>Sun, 22 Jun 2025 17:26:18 GMT</pubDate></item><item><title><![CDATA[Theoretical Practical tank size limit]]></title><description><![CDATA[@Vorg We will slowly get there but no, right now we don't have any kWh capacity battery. As I mentioned, it will be several years before we get there. The fun is to walk this path and make everything open source on the way.
]]></description><link>https://fbrc.nodebb.com/topic/38/theoretical-practical-tank-size-limit</link><guid isPermaLink="true">https://fbrc.nodebb.com/topic/38/theoretical-practical-tank-size-limit</guid><dc:creator><![CDATA[danielfp248]]></dc:creator><pubDate>Fri, 08 Aug 2025 02:26:01 GMT</pubDate></item><item><title><![CDATA[All-copper]]></title><description><![CDATA[@Vorg The reaction is not of elemental iodine with Zinc metal, it is of triiodide with Zinc metal. While this reaction is very exothermic, it is not explosive in this context because of a few reasons:


While all the Zn is deposited at the same spot the oxidized iodine is distributed through the entire catholyte volume, so if the membrane ruptures it takes a while for the reaction to happen, it doesn't all happen at once.


There is a lot of water here, which carries a lot of thermal load. While you can generate a lot of heat on membrane rupture, it isn't even enough to boil the solution at 100% SOC (from my experience). Per point 1, only a small fraction of iodine is able to react at any given point and for more to react flow must be present.


Zn here is bulk Zn, it is not powedered or finely divided at all


I have seen this happen experimentally at high SOC at 2M KI using photopaper. The membrane ruptured at high SOC and what I saw was the volume all shift mostly to one side and the potential drop very quick. Nothing exploded, melted or anything that dangerous. Untreated photopaper is obviously not intended to be a long term use membrane, it is intended as a viable membrane to carry out short term testing that is very easily accessible. To use it long term it is necessary to increase its lifetime with a PVA coating or something along these lines.
The most dangerous scenario in my experience is solid iodine forming in the cathode, blocking flow and causing tubing to unhook, this then splashes charged electrolyte, which is a considerably greater hazard. The use of triethylene glycol seeks to mostly prevent this scenario, but it is still possible if very high currents are used or the cell is overcharged to high potentials (&gt;1.6V).
With the above said, the anolyte and catholyte hold a lot of energy and mixing them obviously instantaneously discharges all that energy. At 10mL of total volume this is not much, around 250mWh but when using larger volumes this is a considerable risk and larger scale devices must be created and tested with this potential scenario in mind.
About the copper, oxygen in it would ruin the electrolyte because it would oxidize Cu+ to Cu+2 and this reaction would also increase the pH of the anolyte. This would eventually cause Cu hydroxide to fall out and kill the device. To recover the cell you would need to purge the electrolyte with Argon, cycle the solution over Cu metal to reduce the oxidized Cu2+ back to Cu+ and add hydrochloric acid to adjust the pH back to the proper level if necessary. To run a cell like this you need to make the system quite airtight and ensure the electrolyte is purged with Argon from the start.
An idea to test for a period under oxygen-present conditions is to keep a piece of sacrificial copper in the anolyte reservoir to make sure that any Cu2+ that is formed is reduced back, so that way you would only succumb to the slow pH up creep. However this means that the CE you measure isn't really fair, because you are not accounting for a huge chunk of active material present there. It can be useful however to cycle and perhaps get some insights into other sections of the system under a regular atmosphere. However I don't honestly know if this is good enough, as the reaction of Cu+ with oxygen is quite fast.
The copper chloride (I) initial electrolyte is usually prepared like this (under copper metal) to make sure there is no Cu2+ present when first loading the electrolyte into the device.
]]></description><link>https://fbrc.nodebb.com/topic/22/all-copper</link><guid isPermaLink="true">https://fbrc.nodebb.com/topic/22/all-copper</guid><dc:creator><![CDATA[danielfp248]]></dc:creator><pubDate>Thu, 15 May 2025 17:22:37 GMT</pubDate></item><item><title><![CDATA[MyStat PCBs for free]]></title><description><![CDATA[@sepi Hi, if you do the selling of the tube, I would order 2 (two) meters.
]]></description><link>https://fbrc.nodebb.com/topic/37/mystat-pcbs-for-free</link><guid isPermaLink="true">https://fbrc.nodebb.com/topic/37/mystat-pcbs-for-free</guid><dc:creator><![CDATA[doho]]></dc:creator><pubDate>Thu, 31 Jul 2025 17:20:57 GMT</pubDate></item><item><title><![CDATA[Connecting potentiostat]]></title><description><![CDATA[@sepi Unless you are very experienced soldering small components I would suggest not doing this. Some of the expensive components are tiny and easy to damage, either by overheating or by soldering multiple legs together and causing shorts. I tried soldering my own mystat 3 times (without success) before I got my first working one from pcbway. I am however, not good at all at soldering.
]]></description><link>https://fbrc.nodebb.com/topic/27/connecting-potentiostat</link><guid isPermaLink="true">https://fbrc.nodebb.com/topic/27/connecting-potentiostat</guid><dc:creator><![CDATA[danielfp248]]></dc:creator><pubDate>Thu, 26 Jun 2025 10:47:13 GMT</pubDate></item><item><title><![CDATA[New ion exchange membrane recipe using water softener resin and PVC cement]]></title><description><![CDATA[@rowow
We don't have the equipment or time to prepare these membranes but if you send us samples of 100-400um thick membranes we can test them out.
]]></description><link>https://fbrc.nodebb.com/topic/57/new-ion-exchange-membrane-recipe-using-water-softener-resin-and-pvc-cement</link><guid isPermaLink="true">https://fbrc.nodebb.com/topic/57/new-ion-exchange-membrane-recipe-using-water-softener-resin-and-pvc-cement</guid><dc:creator><![CDATA[danielfp248]]></dc:creator><pubDate>Tue, 17 Feb 2026 03:21:21 GMT</pubDate></item><item><title><![CDATA[Systems engineering and modeling]]></title><description><![CDATA[@kirk @sepi I think Bert's models are free to download off his site, but if you wanted to read the paper, I'm happy to email them to you or you can reach out to him for a copy.
]]></description><link>https://fbrc.nodebb.com/topic/32/systems-engineering-and-modeling</link><guid isPermaLink="true">https://fbrc.nodebb.com/topic/32/systems-engineering-and-modeling</guid><dc:creator><![CDATA[muntasirms]]></dc:creator><pubDate>Sat, 19 Jul 2025 11:44:12 GMT</pubDate></item><item><title><![CDATA[Tygon chemical for sale]]></title><description><![CDATA[The tubing is gone now, thanks for buying at my store 
]]></description><link>https://fbrc.nodebb.com/topic/40/tygon-chemical-for-sale</link><guid isPermaLink="true">https://fbrc.nodebb.com/topic/40/tygon-chemical-for-sale</guid><dc:creator><![CDATA[sepi]]></dc:creator><pubDate>Tue, 19 Aug 2025 18:40:48 GMT</pubDate></item><item><title><![CDATA[Whole system concept for more security and efficiency]]></title><description><![CDATA[Ah, in the FAQ ... 
Yes, was thinking wrong from other and not so good sources.
]]></description><link>https://fbrc.nodebb.com/topic/25/whole-system-concept-for-more-security-and-efficiency</link><guid isPermaLink="true">https://fbrc.nodebb.com/topic/25/whole-system-concept-for-more-security-and-efficiency</guid><dc:creator><![CDATA[jo.foe]]></dc:creator><pubDate>Wed, 25 Jun 2025 07:49:38 GMT</pubDate></item></channel></rss>