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Everything You Ever Wanted to Know About Electrolyte

This is a subject I get asked about a lot. People keep asking me for the correct formula for mixing up their electrolyte. "How many cups per gallon?" is a common question. I decided to write a complete summary of information about electrolyte to help people understand the subject. If you still have questions after reading this article, please write to me and ask. I will use your question(s) to make this article more complete.


Use steam distilled water only. Look at the label. It must say "Steam Distilled". Reverse osmosis is not acceptable but is sometimes sold as "Distilled" unless you read the label closely. Distilling is the action of heating the water until it evaporates and then re-condensing the water and collecting it. The minerals in the water are left behind, and only pure water results. Minerals in the water will leave a white coating on your plates that will eventually cut down on HHO production. If it gets bad enough, the cell will stop working completely. So this point can't be underestimated.

Use Potassium Hydroxide (KOH) or Sodium Hydroxide (NaOH). Don't mess around with all the other electrolytes you hear about out there. These just don't work well, need constant replenishment, and some of them even create toxic gasses. We prefer KOH because it has better antifreeze properties than NaOH. So if you are in a cold climate, there is no real choice. In warm climates that never get much below freezing you can use NaOH if you prefer.

Whichever you use, be sure to get pure chemical. You don't need lab grade, which is expensive. But don't get a mix with other chemicals such as can be found in some drain cleaners. The other chemicals can ruin your stainless steel plates. Drain cleaners are OK but they must say "Pure Sodium Hydroxide". The common name for KOH is caustic potash. The common names for NaOH are caustic soda or lye. So pure lye, for example, would be pure NaOH and would be OK to buy.

If you live in a small town like I do, then you may have to order your electrolyte from an online supplier. If you live in the United States, you can use the same supplier I do. I use for my KOH, both bulk and for small quantities. For those that live outside the U.S., you'll need to find a supplier in your own country. Shipping these chemicals internationally has so much red tape that I'm not aware of any companies that will do it. So use google and limit the search to your own country. The types of companies that will have it are biodiesel products suppliers, soap making products suppliers, and chemical suppliers.

When you use KOH or NaOH, you don't need to add more electrolyte when you refill your reservoir. Just add more steam distilled water. The only time you'll need to add electrolyte again, is if you flush and refill the system. Note, if you find you need to replenish electrolyte, then you must find out how the electrolyte is getting out of your system. If you can't find an obvious leak, then it's probably being forced into your engine due to an incorrect installation. This is bad and must be solved immediately so you don't ruin your engine. But under normal operation the electrolyte doesn't need to be replenished.

Aside from electrolyte, the only thing you should add to your distilled water is a pool and spa de-foaming agent. The active ingredient in these is polydimethylsiloxane. It always comes in a liquid form with the active ingredient emulsified in water and looks like a thick milky white liquid. We include some of this now in all of our kits. Add a 1/2 - 1 teaspoon per quart. It doesn't bother HHO production at all. If you see foam in your reservoir, be sure to add more until there is no foam anymore. Like electrolyte, you only need to add it once, as it will stay in the reservoir after as the water is used up making HHO. We get ours from the local hardware store and it's just called "Pool and SPA Defoamer". I'm sure specialty pool supply stores would also have it.

Anti-freeze agents: Don't use them. We have tested every form of alcohol in testing to see if we can lower the freezing temperature of the electrolyte. They all cause HHO production to fall dramatically. Despite anything you read anywhere else, don't do it. You can end up ruining your cell as it will get coated with gunk and require complete disassemble and a rebuild to correct. KOH is the best antifreeze agent to use. Just add more for cold climates. You may end up with too strong a mix, and this may cause a small reduction in efficiency, but it will work. Other antifreeze agents won't. For more information about this, including a chart showing KOH concentration vs freezing temperatures, see KOH Freezing Temperatures

Electrolyte and Current

More electrolyte = more current = more HHO. This is actually only true up to a certain logical maximum concentration. After that point the solution will get saturated with electrolyte, and any more added electrolyte will not dissolve in the water, and therefore will not increase the conductivity of the water. But within reason, more electrolyte = more current = more HHO. Therefore we must add enough electrolyte to get the amount of current we want.

Here are the main factors that affect current:

Electrolyte concentration: We've just covered this. More electrolyte = more current. But realize that as you use up the water in your reservoir, the electrolyte stays behind. Therefore the remaining water in the reservoir is getting more and more concentrated because there is less water, but the same electrolyte. The electrolyte concentration increases dramatically when the reservoir is nearly empty.

Temperature: If the cell is warm, it conducts more current. If it is cold, it conducts less. In the winter, you may need to add more electrolyte. This is also the cause of "thermal runaway". This is something that happens with systems that don't have a self adjusting, constant current PWM. What happens is that as the cell starts producing HHO, it warms up. This causes it to draw more current. The additional current causes the cell to warm up more, which causes it to draw even more current. This can keep going to the point where the cell gets so hot it is damaged.

Voltage: A cell is designed to use a certain level of voltage, either 12 or 24 volts. But these are nominal (in name only) voltages. The actual voltage is somewhat less than this when the engine is off, and somewhat higher when the engine is running. But the exact amount is different from vehicle to vehicle. On a 12 volt engine, I've seen voltages range from 14 volts to 12.5 volts in a running vehicle. This difference in voltage can cause the system to need more than double the electrolyte.

Number of neutral plates in the cell: This is really an extension of point 3 above, as this affects the voltage from plate to plate. Our cells are designed so that they all have 2 volts from plate to plate. Here's how this works: For a 12 volt system we use 5 neutral plates between the positive and negative plates. This creates 6 gaps between the positive and negative plates. The 12 volts gets divided relatively equally between each of these gaps, giving us 2 volts from plate to plate. Our 24 volt cell uses 11 neutral plates which works out to 12 gaps and therefore is also 2 volts from plate to plate. This point can be ignored if you are using one of our cells, but some cell manufacturers use only 4 neutral plates, and this will need a dramatically lower electrolyte concentration. Some manufacturers even use less neutral plates and some use none, but these designs should be avoided.

Electrolyte Concentration

The main reasons we can't tell you the correct amount of KOH to use for all applications are due to the points above. It can vary so much that a formula that I use for my car may be double the amount that another user needs, but half the amount that still another user needs. The differences can vary that much. So, I can't tell you how much electrolyte to use. But I can give you a simple procedure to use to work it out for yourself, and once you have it, you can use it in the future for that vehicle.

As long as you are using a constant current PWM (CCPWM), you can't really go too far wrong in this. See the article about these if you're not familiar with them. As long as you have enough electrolyte to get the desired amps you need, then the PWM can handle it from there. You only want to get your concentration in the correct range for optimum operation, but if you aren't exactly correct, it won't matter much at all because the PWM will make the adjustments for you automatically.

If you are not using a CCPWM then you really are going to have trouble, because you can never get the concentration just right. The amps and HHO production will be vastly different between a full and an empty reservoir. Even if that weren't the case, the HHO production will be very different between a cold cell and one that is warmed up. If you add too much electrolyte, you'll get thermal runaway. It's just not possible to have a successful system without a CCPWM. This is why we won't sell a system without one. It just sets a person up for a loss, or the hidden expense of later having to buy a PWM that wasn't planned for.

The following steps will help you determine the correct amount of electrolyte to use. As you do these steps, you'll be adding electrolyte a few different times, not all at once. Measure each amount you put in, and then write down the total. That way, when you get it correct, you'll know your formula for that system.

Also, when you are testing the amp draw on your cell, you need to have the engine running. If the engine is off, the voltage will be much lower, and if you added KOH until it ran correctly with the engine off, it would be way too much for the higher voltages when the engine is running.

If you are not using one of our PWMs with the liquid crystal display that shows the duty cycle, then you should bypass the PWM for these steps. You won't know if the PWM is limiting the amps, or you don't have enough electrolyte. Just bypass the PWM with jumpers from the battery directly to the cell, bypassing the PWM. Then after you get the electrolyte concentration correct, the PWM will be able to make the needed adjustments.

Finally, before starting, you'll need to know what amperage you are trying to achieve. This is different for different engines. So before starting you should see the article, How Much HHO Should I Use? From that article you can work out sensible target amperage. You need to know this in order to get the concentration correct.

The Steps

First a word about safety: KOH and NaOH are extreme irritants. They won't kill you. But if you get some in your eyes, you'll have a very bad day. So safety glasses and rubber gloves are not a bad idea. Also, never add water to the dry electrolyte. The reaction can be quite violent, and it can even spit some chemical into your eyes. Add the chemical to the water, always. You'll notice that the water heats up as the chemical dissolves. This is normal.

Mix about 1/4 cup of electrolyte per gallon of distilled water. Do this in a separate container. If you put the water in the reservoir, then add the electrolyte, it will take a very long time before the cell starts working. The only thing that makes the water circulate in the system is the production of HHO. If you have pure distilled water in your cell, then add the electrolyte into the reservoir, you'll get no HHO production and no circulation. Mix first, and then you'll have electrolyte in your cell.

Pour the mixed electrolyte into your reservoir. Only pour in enough to fill the cell, and leave a little liquid in the bottom of the reservoir. That way if you have to thin it out some, you have some space to add plain water.

Now, run the engine and measure the amps. They will probably be low and so you would then add some electrolyte. Because it is so much easier to increase electrolyte concentration than to decrease it, we start out with a small amount. So that it will shouldn't be too strong. However, if it is too strong, add more water. Otherwise add more electrolyte. Once you have determined that your mix is not too strong, you should fill the reservoir with more of the mix. Now add pure electrolyte until the amps come up to your taget amperage.

The ideal concentration will give you your desired target amperage when the PWM is running at 100% duty cycle, the engine is cold, and the reservoir is full. That way, when the engine warms up (causing more amperage), and the reservoir gets empty (causing more amperage), the CCPWM can still easily adjust to the correct current for you.


I've tried to cover all the factors that affect the correct concentration of electrolyte in your cell. There's actually quite a bit to know about it. It's all pretty simple really, but you have to know these things to get it right. Please contact me if you still have questions about any of this because that would only mean there is something I still need to cover in this document so it answers everyone's questions.

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