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Why have neutral plates in an hydroxy generator? Answered

Hi all,
I've been wanting to build a simple hydroxy generator for using it as a torch.  I've seen about 500 gazillion tutorials and alot of them talk abour having 3-5 neutral plates between each positive and negative plate.
What is the point of this?  Isn't it better to have all plates connected as electrodes?
Also, what's the difference between having 5 neutral plates between positive and negative plate, and just having the positive and negative plates installed farther apart (same distance as if you had the neutrals between them)?



The use of "neutral" plates in an electrolysis cell, divides the cell, so that what you get electrically is a something that looks like a stack of several cells connected in series.

Starting with the trivial case (n=0) of an electrolysis cell with 2 "wired" plates, and 0 "neutral" plates, this cell looks like 1 cell.

Next case (n=1): 2 wired plates with 1 neutral plate. Electrically, this arangement looks like 2 cells, wired in series.

Next case(n=2): 2 wired plates with 2 neutral plates. Electrically, this arangement looks like 3 cells, wired in series.

And so on, and so forth, until n=N, an arrangement with 2 wired plates and N neutral plates, that looks like N+1 cells, wired in series.

This is what the picture looks like to me, but just to be clear, I am going to explain some of my assumptions here. There is a set of rules I am using for to transform some general arrangement of metal plates and water into an equivalent electrical circuit made of lumped components, specifically cells, resistors, and wire.

Three rules:

(1) The inside of a metal plate is made of metal. Electrically it looks like a short piece of wire, and when I draw my equivalent circuit diagram, I draw the insides of plates as short wires. Conduction inside metal is entirely a flow of electrons (e-).

(2) A length of water, also called electrolye, looks like a resistor. Conduction inside water is entirely a flow of ions, e.g. hydroxide (OH-), hydronium(H3O+), sodium(Na+), bisulfate(HSO4-), you know, whatever is in my water besides water (H2O). On my equivalent circuit diagram, I draw water spaces as resistors.

(3) The only place where electrolysis is actually happening is at the surfaces of the metal plates, because that's where the place where electrons, in the metal, meet the ions, in the water. Technically these surfaces are half-cells, either an anode, or a cathode.

I found that in drawing a circuit for this, I had to sort of invent a new symbol for "half cell". My chemistry studies say there is such a thing, but my studies in electrical engineering did not give me a symbol it. So I draw this using a symbol like the one used for a one-celled battery, but with a (1/2) written underneath it, and with a (+) or (-) to designate it as anode or cathode respectively.

As sort of a forth rule in this three-rule set, I assume for circuit elements connected in series, that I have freedom to swap these around into any order I want. The important thing, electrically, about elements connected in series, is that these elements share the same current. The order, which comes first, second, third, etc, is not important. By swapping things around like this, I can simplify the diagram considerably. I can do magic like lumping two complimentary half cells together to make one "whole cell", plus more mundane tricks, like lumping resistors together. E.g three Rs in series, are equivalent to one resistor labeled 3R.

I am hopeful this will become clear in the attached picture-diagrams.

By the way, in case you are wondering why I, or you, or anyone, would want to redraw your electrolysis setup as a circuit, the reason why is because this makes it easy to visualize where the electrical energy is going.

Current flow through the little one-cell battery symbols on my drawing, that electric current is doing something useful in those places. It's making the chemicals I want, and at a rate directly proportional to I=dQ/dt, the current.

Current flow through the resistors is less useful. In those places, the current is making heat, and wasting energy, as dE/dt = I^2*R.

For this last reason, a big, long water space is not useful, because it looks like a big, long resistor.

Anyway, I promised to draw you some pictures, and these are attached below.


I didn't see your first comment as rude. I knew I was either missing something or misunderstanding it. No need to apologize :)

About your circuits:
the one with just 2 plates (pos, neg and a lot of water in between) seems like a waste of time and energy. Putting the plates close to each other seems like the thing to do.

the circuit with the 3 cells connected in parallel is exactly what I was going to do, before reading any tutorial. Sometimes I think I'm just over thinking it and should build first, read tutorials later...

The third circuit with the 2 neutral plates - That what's confusing me.
First question - is it in any way better than the cells in parallel configuration?
Second question - those two neutral plates seem to float in mid air (well, water in this case). What are they connected to? Looking at the drawing it seems like the neutral plates act as both neg and pos at the same time... What am I missing?

I think the reason why people are building this cell design using neutral plates, suspended mid-water as you say, between two wire-connected plates, the reason this is done is to build an arrangement that looks like several electrolysis cells in series.

So maybe you are wondering why anyone would want cells wired in series. Or which is better: cells in series, or cells in parallel?

A quick word about cells in parallel: Building 2 (or N) cells in parallel is exactly equivalent to just building a bigger cell with twice (or N times) the plate area. The trick with alternating wired-plates, like in the drawing I labeled Example 3,


is the same thing as just one cell, but with bigger plate area, same as many small cells wired in parallel.

A D-cell battery is like several AA-cells wired in parallel. It's like the same cell, same open-circuit voltage, just bigger, more plate area.

Back to the question of which arrangement: series or parallel, which is better for your electrolysis cells? The answer to that question depends on the voltage-current character of your power supply.

Often the power supply is some kind of 12-volt DC supply. I mean a lot of the people who build these things are installing them under the hood of their cars and trucks, to try to improve their fuel economy via hydrogen boosting, i.e. mixing the gas produced by their cell with the fuel air mixture to try to make it burn better.

However, the characteristic voltage across a hydrogen-and-oxygen making electrolysis cell is only like 2 or 3 volts. So that's not a very good match to a 12-volt power supply. A better match would be like 6 or 4 electrolysis cells wired in series (since 6*2V=12v, 4*3V=12V). Actually, I think Petercd already mentioned this, so I might be saying the same thing again.

Another trick is to just build, or buy, a power supply that is matched to the voltage of one electrolysis cell, and I know of one company that makes a DC-to-DC converter actually intended for driving a water splitting electrolyis cell, and here's the link:


Regarding your other question of, how to the neutral plates, "floating" mid-water, how to they get connected electrically, there is a old proverb about electricity. I forget exactly how it goes, but it's something like:

"The current always takes the path of least resistance. "

And this is essentially true, at every infinitesimal point in an electrolysis cell, the charge carriers, electrons or ions, sort of have to make a choice: Do I go this way? Or do I go this way? Which way offers less resistance?

Consider that the bulk resistivity,


of the electrolyte is probably 100 or 1000 times greater than that of the metal in the plates. The electric current wants to go through the "floating" neutral plates. It prefers to take that path, because it finds less resistance that way.

To sort of visualize this, I suggest starting with a drawing of a cell with neutral plates, like the one I labeled Example 1,


then draw some blocks of imaginary insulator above, and below, the floating neutral plates. Then ask the question: where does the current flow? What path does the current take? Well, there's only one place it can flow, and that is straight through alternating layers of water and metal.

Then you step back, and say, "Well, but the blocks of imaginary insulator are just an approximation. " And that's certainly true, but if its a good approximation, and I think it is, then most of the current is flowing through the neutral plates, and only a small fraction of the current is flowing around the neutral plates.

I don't know for sure how good the approximation is. The easiest way to find out might be to build a cell with neutral plates and see. Do these "floating" plates have lots of bubbles coming off from them? If so, then that means lots of electric current is going through them.

I mean, that is if you actually need a cell with neutral plates, i.e. you're trying to build something that looks like several cells in series, for to match the voltage across these cells, to the voltage of the supply you're using.

That makes a lot of sense to me. I suspected the metal plates would offer the path of least resistance.

I think what confused me is that the neutral plates act as both anode and cathode at the same time. Am I right to assume that each plate bubbles with oxygen on one side, and Hydrogen on the other?

And not that it really matters as I'm gonna use a DC power supply, but as I'm not interested in separating the gasses, does it matter if I use a DC or AC (Assuming both are 2V 20Amps)?

Yes. Each neutral plate is bubbling hydrogen on one side and oxygen on the other. I mean a cathode layer forms on one side of the plate, and an anode layer forms on the other side. Or at least that's the way I imagine it happening.

In fact it might be a good idea to actually build something, and see if it really works the way same way it works on paper.

I don't know about AC versus DC. I would guess DC would work better. There might be a desire to switch the polarity around occasionally to even out the corrosion of the electrodes, but at a period of like hours, or minutes, rather than every 1/60 of a second.

Corrosion is usually worse at the anode. However, if you've got an anode material that seems happy, you know: doesn't corrode, doesn't build up an insulating passivation layer, and consistently gives you lots of (oxygen) gas... If you've got an anode that works, it might be best to just leave it in those conditions; i.e same polarity, same electrolyte concentration, same current density.

Ahhh, cool.

I've heard of all kinds of options for the plate material, I think I'll test around and see what works best.

Thanks for all the help!

**Please observe** Neutral plates are a complete waste for HHO generation!!

Electrolysis works on the principle of electron exchange, which only occurs at a useful rate through direct contact of water with your positive or negative plates. Neutral plates are only a waste of money, weight, and material for HHO design unless you plan on using them as heat sinks in a dry cell design. If you want proof of this, build your HHO unit with neutral plates and notice how little gas actually comes off the neutral plates.

Everyone always quotes the electrical engineering formulas for capacitance as a reference for why to use neutral plates because it causes a voltage drop from plate-to-plate to get a target of 2~2.4v but the only voltage that the electrochemical reaction cares about is the driving voltage from your hot/energized plates in the solution because these plates actually have a solid path for the current/electrons to get to the H2O for the electrolysis reaction. The reduction in current from using neutral plates is most definitely the result of having a smaller surface area which is actually electrically connected to source power, which means less surface for the H2O electrolysis reaction to take place, which means lower electron exchange and thus current.

HHO generators are not designed to be used as capacitors and if employed as such would be extremely lossy as the electrochemical process that occurs cannot be reversed to get electricity back from the H2 and O2 gas that is still clung to the plate surface. If you are trying to make a HHO capacitor then neutral plates might be utilized but the distance between the plates would need to be extremely close, and one would only use something like this if they were experimenting with a resonance HHO design where a the capacitance value is essential for turning an AC driving voltage.

Please don't be fooled into using neutral plates to lower voltage, it is bad science that has somehow become an accepted aspect of HHO design. There are other means to lower voltage and current to required levels which need to be explored and exploited.

Where on Earth did you read that HHO generator's serve as capacitors?? Because they don't, they are essentially water resistors, and the idea that they work as a capacitors is totally bullshit

In a series cell config, the voltage across 2 plates ( cell voltage) is key to good gas production and efficiency, brute force dc is usually at 2.2V but higher than 2.5V leads to heat and erodes the plates faster.

Common application is usually an automotive scenario, so 7 plates at 12V is 6 cells with 2V across each cell, efficient use of the available voltage.

If you have a PSU that delivers 2 ~ 2.5V at 20Amps then by all means wire them in parallel.

The standard cell gap is 3mm and I have used 9.5mm in some of my cells, but 50mm and up is going to halt any electrolysis.

Suggesting the use of neutral plates for H2 and O2 gas production is the same as energizing a series circuit with 3 capacitors, and connecting a load to the middle capacitor for a series of 3. The load will turn on momentarily and once the capacitor is drained of charge it will turn off. Remember that capacitors in DC are ultimately just open circuits, but if we used AC, building a HHO with neutral plates is an excellent idea to achieve the required useful voltage drop between plates.

However capacitors aren't a fair comparison. If you look at the plates in a hydrogen generator, they don't form a capacitor, as the gap between the plates doesn't serve as a dielectric, it serves as an electrolyte, letting current flow (DC or AC). A proper example would be using resistors to form a voltage divider (which we all know, they do). Plus if hydrogen generator's plates formed a capacitor, no DC current would flow, as you said, capacitors form an open circuit to DC. Also you can't do electrolysis with AC, as when the polarity switches the gases that formed on each side will react the gas that is forming, canceling out, and leaving you with no gas.

Neutral plates are used to decrease the voltage in each plate. The optimal voltage is about 2v, so more than that is waste. So, if you are using 12v for the generator, 12/2=6, so, you need 1 positive and another negative plates and four neutral plates in between them.

Please connect 3 capacitors of equal capacitance in series to a 9v battery and then connect a LED in parallel with the 2nd capacitor (the capacitor in the middle of the series). If the HHO neutral plate theory is correct, then upon measuring the voltage across the 2nd capacitor we would measure 3v (1/3 the supply voltage) and upon putting a LED (load) in parallel with this capacitor it should remain illuminated. This is exactly what the HHO neutral plate theory is claiming, as gas production is an electrical load in this system.

Upon doing this experiment you will find, however, that instead the LED illuminates momentarily and then dims off as the LED consumes the stored charge on the 2nd capacitor's plates. Because the 2nd capacitor is not connected to the DC power supply, once the stored charge is consumed by the LED, the LED turns off. The power supply will not "recharge" the 2nd capacitor because:
1) No displacement current exists between the plates because the power supply voltage does not change (its DC)
2) Capacitors are essentially DC open circuits and capacitors 1 and 3 block any electrons from flowing to both capacitor 2 or the LED.

If this were an AC circuit, the HHO neutral plate theory would be correct and the "neutral plates" would have current being transferred to them and there would be meaningful gas production on these plates. Because HHO generators typically run on DC, these "neutral plates" only act as open circuits, and block the necessary current flow to these plates which is required to generate hydrogen and oxygen gas. "Neutral plates" are either just a trick by scammers to get around making intricate/complex generator designs, an over-simplification to the complex problem of lowering the voltage which was never tested without confirmation bias, or it was just a misunderstanding of basic electrical theory which just kind of stuck as "a good idea" in the HHO community online. I am pleading with the HHO community to stop using "neutral plates" unless you're using AC so that we can start making some significant gas production and bounding advances in this field.

All the chemistry of water electrolysis you could/should want to know:


And by that you mean just hang them in between the pos and neg, completely isolated from the rest of the circuit?

How do they decrease the voltage any more than a water gap of equal distance? In layman's terms, won't the current flow around the plates if they do not form a better path?

Yes, completly isolated. Also, the electricity will always travel by the plates, as the water's resistance is bigger than the plates's one, anyway, by going around the plate the electricity's path would always be bigger than by going trough the plate.

If the plates are not connected to the power supply, all they are is a waste of materials and money.

On a different note, if you are electrolysing water and collecting the gases in a single container, please be aware that this gas (sometimes erroneously called "hydroxy", "brown's gas" or "HHO") is a perfectly stoichiometric mixture of hydrogen and oxygen, and is thus highly explosive. The smallest spark will set it off. In UK schools, it is illegal to detonate more than one litre of the mixture indoors, because of the damage to hearing caused by the explosion.

This is an American video, taken outdoors. Note how the bystanders drop their cameras to hold their damaged ears:

OUCH! I can't imagine this was part of any science class. I hope this is just some teenagers thinking they're smarter than they really are.
In any case, I plan on taking every precaution to avoid that kind of explosive reaction. I want to use the H2+O2 mixture as a torch or a cutter. I have no intention to store the mixture in any form other than plain old liquid H2O.

I know HHO and hydroxy are not real, but everyone's so bent on calling the electrolysis product anything but hydrogen and oxygen gas mixture.

Judging by the teacher-type voice asking "so, what do think just happened?" before the echoes even died, I think this *was* a proper lesson. I've seen similar videos for other kinds of outdoor experiments.

You have seen 500 gazillion tutorials, and yet you still do not understand.

The plates you call neutral plates <i>are</i> connected, and these same plates <i>are</i> electrodes.

Calling these plates, "neutral", is a misnomer, a bad use of the word.

That's what I initially thought, but in some of the more recent tutorials I've read the author explicitly say that they are NOT connected either to anode nor cathode.

Something like +nnn-nnn+nnn-nnn+nnn- (n being neutral).

I suppose that somewhere along the way one author must have thought of something new, or maybe he himself misunderstood something and the misleading info have propagated from there.... We're all human after all.

The term neutral was coined when trying to explain to non technical people that the plates weren't connected to either pos or neg of the psu, yet still form a critical part of the circuit.

Quote: "the plates weren't connected to either pos or neg of the psu, yet still form a critical part of the circuit"

You mean they weren't connected in parallel, but in series? Otherwise I don't really understand how that would make sense.

Hey, um, you've looked at the pictures I drew, right? The neutral plates are not connected, with wires, to the positive or negative sides of the power supply. The neutral plates are connected through the layers of water electrolyte, and also the metal inside the plates.

A stack with two wired plates, on the outside, and N neutral plates placed in between the two plates wired to the terminals of the power supply, looks like a N+1 cells, all wired in a series.

We're still talking about a series cell config, with 6 cells, 2v voltage drop per cell, if you didnt have the neutral plates creating cells between the pos and neg plates then you would just have one cell with 12 V across it.

Sorry about that. It was kind of rude of me to reply to just to criticize the jargon. I mean if y'all call them "neutral plates", then that's what they're called.

I'm going to try this answer again, up at top comment level, except this time with more clarity.