Return to The Matrix with this project recreation. The falling streams of green characters are strange yet calming.

From Quora, the significance of The Matrix computer screen

1. Representation of Reality: The screen symbolizes the digital nature of the Matrix itself. It reflects how the simulated world is constructed and manipulated by the machines controlling humanity.
2. Alternative Perception: Characters like Neo and Morpheus use the screen to perceive the underlying code of the Matrix. It represents the ability to see beyond the illusion of the real world and understand the truth of their existence.
3. Coding Language: The characters are able to read the screen because it displays the Matrix’s code, which is a visual representation of the program that constructs their reality. This code is often depicted in green characters on a black background, reminiscent of classic computer interfaces.

Or, it just makes a cool visualization.

This guide provides instructions on creating a Matrix-inspired visualization with streams of green characters using the Adafruit Metro RP2350. It details how to connect the Metro RP2350 to an HDMI display and upload the necessary code, with no soldering required.

Adafruit Products Summary:
– The project is built using the Adafruit Metro RP2350, which generates high-resolution video output for HDMI displays.
– An HSTX cable is used to connect the Metro RP2350 to a DVI breakout, allowing for easy setup without soldering.
– The Adafruit DVI HSTX library is utilized to write Arduino programs for the project, simplifying the coding process. Adafruit DVI HSTX Library

Read more at Return to The Matrix with the Metro RP2350

On the other hand, (1) presentation skills stay with you through life, and (2) small improvements in presentation skills over months or years can provide you with great advantages longer term. An old saying credited to Thomas Edison claims a breakdown of 1% inspiration and 99% perspiration. However, my own experience with RCU has instead been 0.1% inspiration, 9.9% perspiration, and 90% communication. Had I been unable to communicate effectively, others would have extreme difficulty using RCU, as in even more difficulty than they do now.

There is a lot of speaking experience distilled into this set of posts.

FOSDEM 2025 featured the usual talks about open-source software, but, as always, the conference also offered the opportunity to discover some more exotic and less software-centric topics. That's how I learned about the Flow Battery Research Collective (FBRC), which is building what will eventually become an open-source home battery. Daniel Fernández Pinto represented the collective at FOSDEM with his talk "Building an Open-Source Battery for Stationary Storage" in the "Energy: Accelerating the Transition through Open Source" developer room (devroom).

The open-source battery project has a close cooperation with Utrecht University's FAIR-Battery project and is fully financed by NLnet Foundation. The FBRC is a relatively new project that started last year. Pinto, a chemist, had been doing battery research at home and documenting his findings on a blog since 2019. Electrochemical engineer Kirk Smith discovered Pinto's blog and proposed joining forces. That led to the formation of a project to "build an open-source battery aimed at solar and wind storage in the long term", while aiming to create kits for academic purposes in the short term.

Pinto started his talk with a brief explanation of how lithium-ion (Li-ion) batteries work, since that is the battery technology most of us are familiar with. "In lithium-ion batteries, we're basically just moving lithium ions from a graphite substrate to a metal oxide." He underscored how thin such a battery is: the cross-section is actually just a quarter of a human hair's thickness. "What prevents such a battery from shorting is a 5µm separator", he elaborated. What we commonly refer to as a Li-ion battery is actually composed of thousands of these layers packed and rolled together. The advantage of Li-ion batteries is their high energy-density, but his explanation was followed by the obligatory images of fires at large battery installations. He noted: "any puncture in these tiny layers and it all goes up in flames".

Redox flow battery

Pinto then proceeded to describe an alternative type of energy storage: a redox flow battery (RFB), which he characterized as "more robust for large-scale energy storage". The technology actually dates back to the 1980s. Rather than incorporating solid-state layers, a flow battery consists of two tanks that store the reagents: a positive electrolyte (a solution that accepts electrons) and a negative electrolyte (a solution that donates electrons). Each tank has a pump, circulating both solutions within their own circuit (tank and pipes), with a membrane in a cell in the middle where the fluids meet and exchange electrons. This approach is easily scalable: the tanks can be enlarged if greater energy storage is needed, while the cell size can be increased if more power is required.

Naturally, the question arises whether RFBs can compete with other battery technologies. Pinto presented a chart with five variables: energy density, power density, safety/sustainability, initial affordability, and cycle life. This clearly illustrated that RFBs are not nearly as dense as Li-ion batteries: "They have probably a tenth, or even a twentieth, of the energy density of lithium-ion batteries." However, they hold significant advantages in safety, affordability, and cycle life.

As for safety, RFBs are aqueous systems, "so they don't catch fire". The reagents are generally also more environmentally friendly than the chemistry in Li-ion batteries, Pinto noted. Additionally, "if something breaks in the cell, you can take it apart and replace it", and the reagents can be simply replaced if they stop working. "In a lithium-ion battery, any small failure is critical and destroys the battery."

Why an open-source battery?

"There is currently no open-source battery initiative at all", Pinto stated, whether for Li-ion or flow batteries, hence the motivation for him and Smith to establish one. He is aware of some other open-source projects that aim to reproduce "just a cell", but upon reading the research papers, he realized that there's a lot of missing information, such as instructions on how to build the pumps, reservoirs, and electronics.

Regarding this matter, Pinto said that flow-battery research faces reproducibility issues: "a lot of researchers publish completely different results because of their varying setups, and we wanted to create a cell that could serve as a standard cell for flow battery research". Even though the FBRC intends to sell kits with battery cells, Pinto emphasized that they want everyone to be able to build the cells on their own.

Roadmap

By the end of 2024, the FBRC had completed a bench-top battery cell, with a cell area of less than 10cm², capable of supplying a low voltage and low current. This will evolve into the kit that the FBRC plans to sell "probably this year or next year". As the project is open-source, buying the kit isn't necessary, since anyone can build the bench-top cell following the provided instructions. "We're currently testing chemistries and different materials", Pinto said, to deliver a kit with reproducible results.

By mid-2025, the FBRC aims to have a large-format cell with a cell area exceeding 600cm², capable of supplying low voltage with a high current. Although this will still be a single cell, it should be scalable for larger-scale energy storage. Then, by the end of this year, Pinto hopes to have built a stack of tens of these large-format cells, capable of supplying the high voltage and high current to power a house.

The goal is to replicate something akin to Redflow's ZBM3, which is a 10kWh zinc-bromine flow battery with a continuous power rating of 3kW. Pinto's mention of Redflow was no coincidence, the company went bankrupt at the end of 2024, and that is part of why he's so keen to make an open-source battery. "Redflow invested a lot of time in these cells, which are pretty good. If this had been open-source, people could've used the knowledge to start other businesses, or even build the batteries themselves."

The cheapest pump that works

Pinto also described some of the prototypes that they built. The first prototype of the battery cell was intended to be built from polypropylene, with silicone gaskets and small diaphragm pumps, but the design had numerous possibilities for leakage and other problems. They actually 3D-printed this design with resin, "because we never managed to print polypropylene well enough". Regarding this initial design, Pinto said: "None of this worked. The tubing didn't work, the cell didn't work, the pumps didn't work." To control the pumps, Pinto used an Arduino and an inexpensive motor driver "in total costing less than 20 euros for the electronic part".

In the second attempt, they had polypropylene bodies manufactured, and the diaphragm pumps were replaced by peristaltic pumps. The design saw several improvements, and Pinto showed a video of the pumps in operation, adding "that pump is not supposed to be orange", but was, because it had leaked orange fluid. This was all conducted in Pinto's apartment, he said, joking that he was still standing, "so it's not that dangerous".

Then they changed to a second design trying to prevent the leaks, and the pumps were changed once again. Pinto explained this choice: "We began with the cheapest possible pump we could get, I broke it, and then we moved to the next one. I've been doing that iteratively, breaking every tier of AliExpress pump until I had the cheapest model that works."

This second design worked pretty well, initially with Zinc-iodide as the chemical, since this is readily available in the EU without requiring a license to buy chemical materials. "It's not like you can drink it, but it's not extremely toxic", Pinto added. They did some tests, and this design yielded around half of the energy density of commercial flow batteries.

In flow-battery research, the membrane in the middle is traditionally an expensive Nafion membrane. In contrast, the FBRC's design uses "a very fancy microporous membrane that's called photopaper". According to Pinto, this still exhibits some leakage and resistance, explaining that the resulting energy efficiency of 65% is not particularly high, "but it's very cheap to achieve".

Following this, Pinto showed that they can also achieve higher densities, "at the level of a commercial flow battery", although the graph stopped at two discharge cycles because other parts of the system failed at that point, such as the tubing and pumps: "As things become more energy-dense, they become more reactive. We only had two cycles here because of the corrosion."

Thus, for the next step, they acquired a beefier, impeller pump "the size of a fist". While the previous pumps could pump 60 milliliters per minute, this new pump manages 6000mL per minute, which is necessary to scale up to the large-format cell.

Getting involved

Pinto concluded his talk by describing some ways to get involved in the project. Firstly, individuals can assemble a kit using the online documentation. "Nobody has attempted this, so we're not sure if the instructions are any good", Pinto joked, adding that "we want to make the documentation better". Additionally, just testing whether 3D-printing the pieces works is also valuable "because we need to make sure that the pieces can be printed on a range of printers and with different materials".

Similarly, individuals can also assist by testing various tubing materials or pumps. Additionally, when the project scales up soon, building and testing larger-scale cells will be useful, although Pinto advised that this should only be done with water "because we don't want anyone to die helping us". Lastly, from an electronics standpoint, the project doesn't have a battery management system yet, which is essential for larger-scale flow batteries.

The Flow Battery Research Collective is an intriguing initiative to develop an open-source home battery. Pinto and Smith have clearly focused on an approach that is affordable, safe to handle, and with parts and chemicals that are easy to source. Hopefully their projects can make battery research reproducible and help to democratize home batteries.

[While I was unable to attend FOSDEM in person, I watched the live-stream of the talk.]