Selecting a Battery Charger and Electrolyte for Electrolysis

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bob in CT
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Selecting a Battery Charger and Electrolyte for Electrolysis

Postby bob in CT » Fri Dec 25, 2009 8:54 am

There have been a number of questions about the power supplies for setting up an electrolysis tank. I wrote this article to explain in simple terms what we actually need as a minimum and why. Since electrolyte concentration is related, I have also included some information to explain the mystery of what the electrolyte is and how it helps our electrolysis tanks work. Most of us use 12 volts, but there is no specific requirement for 12 volts. It just happens to be a convenient voltage available from a battery charger. The higher the voltage, the more water is split. While seeing bubbles gives one comfort that the process is working it is not necessarily desirable as you are releasing hydrogen and oxygen.

Water splits with electrical current at a thermal neutral voltage of about 1.4 volts. The more voltage, the more water is split so 6 volts will make more hydrogen than 1.4; 12 more than that; and so on. That is why when someone asks about a super-duper 48 volt power supply for a welder I strongly urge that it not be used as the only thing it is going to do is release more flammable gas.

Therefore, the ideal power supply will be in the area of 1.4 volts or less. Since these are not commonly mass produced and sold in Big Box stores for $19.95, we use battery chargers. Due to the nature of the electrochemical cell, automatic chargers do not work. They "think" the "battery" is charged and go into idle mode. So a manual charger is in order. I use a 6 volt setting on mine, but if you have 12 volts only this will work just fine.

Amperage is what is doing the work. The more amps you can put through the cell the faster the part will be cleaned. With everything tip-top clean I can pull 18-20 amps at 6 volts on a 189 plow beam and have it in and out in about an hour. You can't do this with a $19.95 charger, however, as it does not have the amperage. I have a portable charger that weighs about 35 lbs that has a solid copper wound transformer with silicon rectifiers. Made in USA. It is like comparing a $9.95 throw-away electric drill with a heavy duty Milwaukee Hole Shooter. But that is only part of the story.

You have all heard about electrolytes. Many use TSP, but in some parts of the county this is hard to find. Good old fashioned washing soda works great, but the last time I bought it, it was marketed as "activated baking soda". Look for the real name, sodium carbonate (not bi-carbonate) on the ingredients label. What does TSP or washing soda do? If you connected your parts and put them in pure water and turn on a power supply the size of your garage nothing would happen. This is because pure water is not conductive. Add a thimble of TSP and some current would begin to flow. To understand what is going on you need to look at the TSP or washing soda electrolyte as the wire or pipe that the amperage can pass through. I think we all would have a good idea what would happen if you wired an electric stove in your kitchen using some audio speaker wire to save money instead of a #8 wire. As soon as you turn on the stove the wire would burn up because it does not have the capacity to pass that much current. The same thing goes on in the electrochemical cell but instead of burning up a wire, the electrolyte (water plus whatever you used to make it conductive) limits the amount of amperage that can pass through the cell between the electrodes. So with a thimble of TSP, the power supply, no matter how big, can only do so much. If your power supply has an amp meter, you can start with pure water and add a little electrolyte and watch the amps register. Add more and you will get more amps. That is why I compared it to a pipe earlier. The more concentrated the electrolyte, the bigger the "pipe" for the amperage to travel through. The lower the concentration or conductivity, the more resistance you have in the cell and your power is just heating the water and not doing the work you want it to do. Here is the rub: with a budget charger using a lot of electrolyte will drive your charger at the maximum capacity. Lower cost chargers are not rated for 100% duty cycle and may burn it out with time, so in this case too much conductivity is not a good thing. So adding more TSP or washing soda is almost like stepping on the gas pedal to dial up more amps.

A cell is a little bit more complicated than that, however. The larger the surface area of the part, the more amperage it can draw. The anodes you use need to have the same surface area to get the full cell performance, especially if you have a lot of parts to clean and don't want to wait 24 hours to do each batch. Keep in mind that the moment you start the process an anode begins to degrade so even if it was equal in surface area when you started, once it gets covered with crud, the effective surface area is being reduced. This is why you will see amps start high and then tail off with time. It is also why I remove and clean my anodes after every batch. I have several rebar rods with lawnmower blades or harrow discs welded to them. If I am doing small parts I only have to change one of the anodes on each batch. I have a couple extra that I have cleaned and ready to go so I just swap them to keep my tank productive.

My electrolyte solution is very concentrated. I must have 10 lbs of washing soda and a box of TSP in my 55 gallon tank which probably has 40-45 gallons of water in it depending upon when I top it up. You can do this if you have a heavy-duty charger. If you don't, I would set up the cell with a average sized part and as large as an anode area as practical and add TSP until the amperage on your charger climbs to an appropriate level considering the capacity and duty cycle of your charger. If you have a 6 volt setting you can use that and you will release less hydrogen and oxygen into your workspace.

So how much electrolyte should you use? 1 kilo or 2.2 lbs to approximately 40 US gallons of water or 3/4's of a 55 US gallon plastic barrel seems to be about right for a basic charger. Do the math if you are setting up smaller or larger tanks and don't worry about getting it perfect. Remember that the water will evaporate or get converted into gas as you use it so the concentration will change. Just add more water and you will be back to your baseline. There is no need to ever change it. This is not a chemical reaction so the solution does not wear out. If anything, it gets "stronger" when water evaporates.

IF you have one of the old style heavy duty chargers, you can add a LOT more electrolyte if you want to soup up your tank. I started with a kilo of TSP. Then I added 5 pounds of washing soda. Then I added another 5 pounds of washing soda. It was something to see the amp meter to jump right up to 20 amps at 6 volts when that second box was dumped in. I need to emphasize a couple of things though. First, this is a pretty caustic solution. Not enough to burn your skin, but I do not put my hands in it and you do not want it in your eyes- but that is the case for the weaker solution too. Next is you need the right battery charger or you will burn them out. If you experiment, try it in a small container first. If your big tank is too concentrated, drain some out and add water. No need to toss it all and start over. A final note on electrolytes: I have read that the TSP retards or eliminates the development of flash rust. This could be and it could be related to the success of phosphate type primers and coatings used for that exact purpose. Even though I use mostly washing soda in my tank, I still get no flash rust. I have never set up a tanks using just washing soda to see if there is a difference. I can say that I have zero problems with parts flash rusting.

Power supply ideal? I would love to try a 1.4 volt DC supply with adjustable amperage up to about 30 amps. I have been looking for a low voltage supply, something like those little cubes that are used for charging cell phones and powering answering machines to experiment with a small cell for tiny parts. I save all of those little supplies when I junk a printer or other DC device. You never know when they will come in handy and they have quite a range of voltages. I am using an $80 manual power supply made by Rizk National Industries. I don’t see it in their on-line listing but they made quite a few different models so if you are interested give them a call. They are very nice people.

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