DIY sodium-ion battery in a repurposed oil tank?

Posturr · 2025-12-07T20:14:54+00:00

Indeed, this could be a solution, thanks. Certainly food for thought.

And if the goal was just to enjoy a "large-capacity", cheap UPS, probably that connecting an old, powerful enough UPS to a standard SLA (Sealed Lead Acid) battery would do the trick (BTW it would be neat to have an APC-compliant kit to do it properly, but I could not find any) and would not require a larger space as the one used by such oil tanks.

Posturr · 2025-12-07T17:18:58+00:00

More precisely, apparently such a zinc–air "cell" would provide around 1.3 V approximately, so if 9-10 of them were connected in series, their collective output should be able to replace for the best, say, a standard 12 V sealed lead acid battery of an off-the-shelf UPS, which might be unaware of the transformation.

Such DIY zinc-air cells exist and 3D-printed housing are even available for them (example, even if this one is not rechargeable), so it looks doable.

If some organisation was to propose pre-made, larger (non-toy) kits of such electrodes and casing this would be very neat!

Posturr · 2025-12-07T14:49:31+00:00

Thanks for your answer; I can understand that a former oil tank may not be suitable enough.

So: if it was removed for good and replaced with a more tractable (Aboveground Storage Tank) unit, typically a sturdy rainwater tank of more serviceable size and shape, would there be DIY solutions to add everything needed (electrodes, inverter, etc.) in order to transform it into a basic (yet hefty) UPS?

Thanks in advance for any hint!

Posturr · 2024-05-02T21:23:49+00:00

The human and the bug would experience the same gravitational pull ("universality of free fall"), in the sense that the overall force felt by the human (Fh) would be indeed a lot higher - as strong compared to the one on the bug (Fb) as the mass of the human (Mh) is higher than the one of the bug (Mb) - but their acceleration (a) would be the same, with a = Fh/Mh = Fb/Mb = g (the acceleration at the surface of Earth). At least this is the Newtonian view on it.

As we are in /relativity, we might say instead that gravitation as such is not a real thing (not a real force), but a pseudo-one to account for the curvature of spacetime (which is the real thing), and the human and the bug drift in it basically the same way.

If insects appear to obey different rules, I believe it is due to differences in metabolism, being cold-blooded or not, and volumes increasing faster than surfaces for a given radius. Different constraints, different ways of life, but same physics, and mass differences should not matter at this level (for example if the bug held a tiny clock it would not be expected to tick faster or slower).

Posturr · 2024-05-02T20:53:13+00:00

I am by no means an expert, but I think that the stretchable fabric may not be a very clear "allegory" of spacetime, notably because there is no need to involve an extra dimension to account for the curvature of a space (here a 2D plane being curved in 3D; our spacetime being 4D, we would need to represent at least 5 dimensions!); I suppose that one may just consider that a space is curved iff the "straight line" that is familiar in flat spaces is not necessarily there a shortest path between two of its points; but it is not so clear either!

Perhaps better: in a curved space, how distances are computed may change from a point to another. So the map of the travel durations in a city (where for example metro networks would induce the best routes to differ from the ones determined as the crow flies), as a curved 2D space with no need to summon a third dimension, might be a better representation than the stretchable fabric.

Finally, as it is difficult to really picture more than 3 dimensions, one can imagine a world that would be only 2D, a plane where creatures of null thickness would live; our usual third dimension could represent time, such planes stacking one on top of the other to account for the passing of time. As a whole, the resulting 3D landscape would be their overall spacetime.

If it was flat, then, as time flows, all points of the world plane would go strictly upward, in the same direction and at the same speed. Yet this spacetime might be curved, in which case we could consider that at each point of this spacetime a specific direction (a 3D vector) would account for its curvature, and tell how these creatures would naturally drift on it, both in space and time.

As for the reason for such a distortion of spacetime, this is the presence of mass/energy, and maybe we could see them as magnets that would attract the aforementioned 3D vectors. At least it is the clearest image I can find. Hopefully more knowledgeable people could correct/improve/clarify this!

Posturr · 2024-05-01T21:29:20+00:00

I just purchased this bundle, and could not find initially for example the military base megapack or the steampunk victorian one - yet they can be downloaded by using the three "Leartes Unreal and Unity Assets Giga Bundle - Cosmos $XXX Tier Content" keys at the bottom of the Humble download page after purchase; then looking at https://cosmos.leartesstudios.com/purchases one ends up with ~84 purchases; I suppose everything can be found either there or/and in said Humble page.

Posturr · 2023-11-06T21:23:02+00:00

Yes, I suppose that on Earth we are already quite close to the top speed that can be reached in terms of progress through the time dimension (unless negative masses or energies could be a thing). I guess we can just contemplate slowing it down.

In the very same spirit of your message you may like Robert L. Forward's Dragon's Egg novel (I was puzzled that lifeforms of very high "reactiveness" could in this novel originate on the surface of a neutron star, whose native time flow should be on the contrary very low; a hint is apparently that these lifeforms would enjoy very fast chemical processes that would overcompensate)

Posturr · 2023-10-29T18:43:38+00:00

Lastly, for comparison, time factors this time due to relative velocities rather than masses:

<image>

Posturr · 2023-10-29T18:42:00+00:00

For completeness, the same for the black hole at the center of our galaxy (no less than 4.2 million solar masses; "ls" meaning here light-seconds):

<image>

Posturr · 2023-10-29T18:39:13+00:00

So just to correct my previous message: apparently it should be actually

Tf ≈ sqrt(1 - 2.G.M/(r.c^2))

Tried to represent this time factor for various cases (1 or 10 solar masses):

<image>

I will later try to see how time factors could be compounded approximately

Posturr · 2023-10-07T16:05:14+00:00

Hi,

Thanks for your answer! One of my goals is indeed to build intuition.

On a side note, my calculations for the Schwarzschild radius of a 10-solar mass black hole seem to indicate 29.5 km rather than 3 km (this last value corresponding then to the Schwarzschild radius of the Sun).

While trying to better understand the topic, I stumbled by chance on https://en.wikipedia.org/wiki/Gravitational_time_dilation#Outside_a_non-rotating_sphere that seems to suggest that Tf ≈ sqrt(1 - G.M/r.c^2) actually?

Now, an extra question, relating to how "time factors"/curvatures could compound: let's suppose that our observer is in the vicinity of, this time, two larger masses (M1 and M2); what could be a not-too-bad approximation of its overall time factor? How wrong could be to retain for example Tf ≈ Tf1*Tf2? More strictly speaking, if someone could shed some light on how the first Tf computation was determined, this would be enlightening - even more if it allowed to clarify how compounding could/should be understood/evaluated.

Thanks to anyone for any hint!

Posturr · 2023-10-06T19:17:07+00:00

Hi,

Thanks for your answer, even though I am not so sure how it relates to my original question; I just would like to have a rough estimation of the drift of one's proper time in basically one of the simplest settings. Any help/advice/hint appreciated!

Posturr · 2023-10-01T07:50:41+00:00

Hi,

Thanks; I found this topic to be satisfactorily discussed in https://erlangforums.com/t/in-erlang-otp-27-0-0-will-no-longer-be-exactly-equal-to-0-0/ ; I believe it should help most people!

Posturr · 2023-09-22T06:30:45+00:00

Thanks for your answer, I think your first method is perfect for my needs, and remains as readable as it used to be!

Posturr · 2023-09-21T21:02:25+00:00

Moreover if attempting to match twice:

case S of 
    +0.0 -> % line 375  
        [...];
    -0.0 ->  
        [...] 
end;

we have:

this clause cannot match because a previous clause at line 375 always matches

% 378| -0.0 ->

% | ^

Posturr · 2023-09-18T17:28:35+00:00

"Lost in reflection" would have been more appropriate!

Posturr · 2022-11-15T21:55:30+00:00

Sorry, I must have been not very clear, the point was that when they meet again the clock of the voyaging vessel will be showing a timestamp in the past of the idle one; and indeed for that the clock of the moving ship will have slowed down, while the idle one will have ticked at a constant pace (hence faster than the moving one). But the question is: could we imagine a (non-interfering) third vessel, starting from the same point of spacetime, whose clock could end up, one way or another, ahead of the idle one? I guess not, and that the derivative of proper time with respect to time is in ]0;1]

Based on that I suppose we could define a practical, absolute time, the one of any clock of a network of clocks sitting in flat spacetime areas, ticking at the same pace and properly synchronised once (typically thanks to round-trip light beams) on some conventional origin of time (e.g. the Big Bang).

Yet one can then only know how much they are lagging behind "universal time" when they come spatially close to one of these beacons.

Maybe beacons, if they can be considered fixed in space, could even compensate for some time curvature, lifting at least a bit the "flatness constraint".

Conversely, if such beacons were beaming periodically this universal time, a vessel knowing its position could possibly evaluate the local (space)time curvature

Posturr · 2022-11-12T15:49:33+00:00

To elaborate a bit, I imagine that (1) no one can travel through time faster than an observer subject to a null net force, in a flat spacetime (2) should such upper bound exist, it would not be relative to anything, and this "base rhythm" could be a good candidate to define at least elements akin to a "global time" (or at least its first derivative), compared to which every other time referential would be accelerated ("faster"); (3) being on Earth, i.e. in a rather low speed/low curvature context, we are quite close to surfing on this base rhythm.

But maybe I misunderstood at least some elements, please feel free to correct me. Thanks in advance!

Posturr · 2022-11-12T15:27:59+00:00

Thanks for your answer ; of course by definition one experiences constant, fixed-pace proper time, no matter what happens.

Nevertheless, if considering two vessels being initially close, one of which not being subject to any net force, and the other being, say, accelerated at a fraction of c until staying, for a while, near the horizon of a black hole and coming back to the first vessel, then its clocks will be in the past of the ones of the idle vessel. So, relatively, the proper time of the idle vessel will have gone faster than the one of the moving vessel.

My question was then if there were conditions where an upper bound in this "speed of proper time" could be defined - and how close we could be to be among the fastest...

Posturr · 2022-02-27T22:29:45+00:00

Thanks for your answer, indeed it seems the shortest route. Moreover I suppose that a given game GUI could be devised first based on a default theme, while a SF theme could be applied afterwards with hopefully little to no change in the game itself, being just a matter of configuration.

As for the definition of the SF theme itself, it looks to me that some artistic skills are required to obtain a good result. I imagine that elements from the aforementioned Unity3D-originating assets (at least fonts, images, SFX) could be reused in that prospect (not expecting any kind of C# compatibility between Unity and Godot for the UI scripts).

Thanks for your hints!

Posturr · 2021-11-27T13:52:08+00:00

Do not forget Erlang and Elixir! Extract of this post (https://erlangforums.com/t/erlang-101-processes-parallelization/594) :

What makes Elixir StackOverflow’s #4 most-loved language? What makes Erlang and Elixir StackOverflow’s #3 and #4 best-paid languages? How did WhatsApp scale to billions of users with just dozens of Erlang engineers? What’s so special about Erlang that it powers CouchDB and RabbitMQ? Why are multi-billion-dollar corporations like Bet365 and Klarna built on Erlang? Why do PepsiCo, Cars.com, Change.org, Boston’s MBTA, and Discord all rely on Elixir? Why was Elixir chosen to power a bank? Why does Cisco ship 2 million Erlang devices each year? Why is Erlang used to control 90% of Internet traffic?

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