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Electrolyte Concentrations

With regard to the amount of electrolyte to use, it must be noted that one cannot simply give a rule that is generally applicable, since the amount to use is a function of:
  1. The number of water compartments (cells); 4, 5, 6 7, or more.
  2. The spacing between the electrodes
  3. The desired starting/ending temperature required after a certain amount of time has elapsed.
  4. The type of Electrolyte.
  5. The type and grade of metal.
  6. The resistance of the water.
  7. Altitude
  8. Environmental Temperature

For a Series Cell with 6 water compartments, you should need about 1 tablespoon of NaOH or KOH for every liter of water. Add enough to start with a current draw of say 10 amps when the water is cold (but no more). As the water heats up, the current draw will increase. If it gets too hot for you, use less electrolyte.

Here are some figures to use as a guide when operating a 6 series tube cell configured with 8 inch length tubes, with the smallest tube 1 inch and the largest tube 4 inches in diameter. The configuration will hold about 1 liter of water without overflowing the upper rim of the inner tubes and we do not want the amp flow to exceed 16 amps within the first 2 hours. Add 1/8 cup of NaOH to 1 liter of distilled water (6 teaspoons, or 30 ml of NaOH).

Here is the typical temperature, amp flow and LPM for that mix concentration....and cell configuration:

  • Startup   5 A      Cold  0.5 LPM
  • 10 min.  7.5 A    0.75 LPM
  • 1/2 hr.   10 A     1.0 LPM
  • 1 hr.      12 A     104 deg F, 40 C ,     1.2 LPM
  • 1.5 hrs  15 A     122 deg F, 50 C,      1.5 LPM
  • 2 hrs     16 A     136.4 deg F, 58 C,   1.6 LPM
  • 3 hrs     17 A     149 deg F, 65 C,      1.7 LPM
  • 4 hrs     18 A     163.4 deg F, 73 C,   1.8 LPM
  • 5 hrs     18 A     165.2 deg F, 74 C,   1.8 LPM
  • 6 hrs     18 A     167 deg F, 75 C,      1.8 LPM
  • 7 hrs     18 A     165.2 deg F, 74 C,   1.8 LPM
  • 8 hrs     18 A     163.4 deg F, 73 C,   1.8 LPM

As you can see, after 4 hours of continuous operation, the temperature stabilized at +- 165 degrees F, 74 C, which is ideal! Note that the temperatures were measured during bench-testing with an outside temperature of +- 70 F, 21 C. If the cell is installed in a vehicle with sufficient air flow, the cooling affect of the air flow could stabilized the cell at a lower maximum temperature. Once the cell reaches operating temperatures between 140-158 F, 60-70 C, it consumes about 75 ml of water every hour of operation. So 1 liter of water should last about 13 hours of driving time. 15 amps does not place too much of a burden on the car's alternator, thus it should not effect fuel economy gains.   ,

Electrode spacing is another factor that influences the amount of electrolyte needed to allow a particular amount of amperage draw. In a series cell, spacing less than 1/16 inch, 1.5 mm, can inhibit the bubble flow and gas production at higher amps, because the electrolyte starts foaming and crawling up the tubes. That can reduce surface area efficiency. In addition, the amount of gas is not related to the amount of water left in the container; except when no water is left. The amount of gas produced is determined by the amps. So, you could have peak gas production right up until the cell runs dry. Whether you have 100 ml of water left or 900 ml left, that does not determine the amount of gas. The temperature of the water determines the resistance of the electrolyte and thus influences the amps that are flowing. So, with less water in the cell, the temperature is likely to be higher, and more amps flowing, than with more water. Example, let's say we have only 100 ml of water left in the cell, with a given amount of NaOH, and the water temperature is about 158 F, 70 C. We might have 20 amps of current flowing, resulting in 2 LPM gas production. If we were to add 900 ml of ice cold water to reduce the temperature to 104 F, 40 C, one might find that amps suddenly drop to 15 A, and thus have only 1.5 LPM of gas production. Adding water can actually reduce the gas production. That is an extreme example but I use it to illustrate that the amount of water left is not the issue, rather the concentration of the NaOH in the water. It makes the water more conductive, rather than the temperature itself.

7 Series Cell design:

In order to exceed 100% Faraday calculations, we must go for a 7 series cell (8 plates) if using 13.8 operating volts. The most restrictive drawback to consider is how long it takes a 7 series cell to warm up to a high enough temperature to get decent gas production. When driving a car, we do not have the luxury of having the cell sitting on a bench for hours to reach decent gas production. We want good gas production within a few minutes of driving. Another drawback of the 7 series cell is that it needs 6 times more electrolyte in order to pass the same amount of current as the 6 series cell above. As we know now, the electrolyte is indeed slowly being consumed along with the reaction. This makes the 7 series cell more sensitive to electrolyte water mix, so it will have to be topped up, along with more electrolyte, a lot more frequent. However, there are advantages. A 7 series cell would be ideal for powering a generator 24/7, or a commercial diesel truck that seldom shuts down, or an HHO furnace that operates full time.

A 7 series cell typically needs 7/8 cups of NaOH to produce 4 amps at startup; 42 teaspoons. Even more frustrating is the slow warm up time. After an hour, the amp flow will only be around 5 amps, and even after 2 hours, it will only be around 6 amps. We need a decent amount of amps to generate a decent amount of gas. After 2 hours, this 7 series cell configuration, will only achieve about 720 mlpm; compared to the 6 cells 1.6 LPM. That is why 7 series cells are impractical for a car; plus the fact that that much NaOH concentration certainly is not very user friendly.

  Number of Plates : References the difference in efficiency comparing cells with 2, 3, 4, 5, 6, and 7 plates in Series. A chart shows the required amperage needed to produce 1 LPM of HHO -- for each cell plate configuration. It also shows the plate voltage, and Current Density needed for Continuous operation.


Shorten Warm-up Time

The scenarios above are both using straight DC voltage supplied by a battery/alternator. The cell amperage is controlled by the construction design, temperature, and by the electrolyte mix. It is possible to increase the startup amperage. gas production, and control temperature by pulsing the amperage to the cell. This can be accomplished with a Pulse Width Modulator (PWM).

The PWM pulses the DC voltage to the cell. Pulsing the voltage turns the current on off on off on off, thus reducing the heat caused by constant current flow. In other words, just as the current starts to flow, it gets stopped. The series of starts and stops happen instantaneously.

The PWM allows you to regulate the amperage (current). This provides runaway control over the cell. The longer the cell runs on DC, the hotter the water will get, the higher the amps will go. Eventually you will blow a fuse, pop a breaker. The PWM solves that problem.

Some PWM's are self regulating; meaning, they are made to operate at a constant amperage, even as the water gets hotter. You set the maximum output, and forget it.

Please be advised: A PWM will not increase the capability of your Hydrogen Generators HHO output. It will do just the opposite. It will restrict the output; based on what you set it to produce.

During winter months, we need more electrolyte in the water because cold water does not conduct electricity as well. In summer months, we need less electrolyte in the water because hot water conducts electricity much better than cold water. During periods of hot and cold, you are screwed; unless you have a PWM. The PWM allows you to use more electrolyte, and control the output of the HHO generator.



KOH Concentrations


KOH, Potassium Hydroxide Concentration in Water, calculator:

Sodium Hydroxide in Water
  Temperature in degrees Centigrade (C)
  0C / 32F 15C / 59F 20C / 68F 40C / 104F 60C / 140F 80C / 176F 100C / 212F
Concentration (% Weight) Density (kg/L)
1 1.0124 1.01065 1.0095 1.0033 0.9941 0.9824 0.9693
2 1.0244 1.02198 1.0207 1.0139 1.0045 0.9929 0.9797
4 1.0482 1.04441 1.0428 1.0352 1.0254 1.0139 1.0009
8 1.0943 1.08887 1.0869 1.0780 1.0676 1.0560 1.0432
12 1.1399 1.13327 1.1309 1.1210 1.1101 1.0983 1.0855
16 1.1849 1.17761 1.1751 1.1645 1.1531 1.1408 1.1277
20 1.2296 1.22183 1.2191 1.2079 1.1960 1.1833 1.1700
24 1.2741 1.26582 1.2629 1.2512 1.2388 1.2259 1.2124
28 1.3182 1.30940 1.3064 1.2942 1.2814 1.2682 1.2546
32 1.3614 1.35200 1.3490 1.3362 1.3232 1.3097 1.2960
36 1.4030 1.39330 1.3900 1.3768 1.3634 1.3498 1.3360
40 1.4435 1.43340 1.4300 1.4164 1.4027 1.3889 1.3750
44 1.4825 1.47200 1.4685 1.4545 1.4405 1.4266 1.4127
48 1.5210 1.51020 1.5065 1.4922 1.4781 1.4641 1.4503
50 1.5400 1.52900 1.5253 1.5109 1.4967 1.4827 1.4690




NaOH Concentrations

Sodium Hydroxide Concentration Calculator
This is a table of density (kg/L) and the corresponding concentration (% weight) of Sodium Hydroxide in water at a temperature of 20 degrees centigrade. The table was taken from the chemical engineering handbook. The calculator does automatic interpolation calculation for density or concentration values that are between those in the table. In effect, any value within the range of the table can be calculated. Just input the density of the solution and the calculator will compute for the corresponding concentration. Or input the concentration to get the corresponding density. Please input only one value and leave the value to be calculated blank. In practice, density is determined by means of a hydrometer or by weighing a known volume of a solution. This calculator can be used in conjunction with the other three sodium hydroxide calculators in this set. 
Concentration (% Weight) 0 1 2 4 8 12 16 20 24 28 32 36 40 44 48 50
Density (kg/L) 1 1.0095 1.0207 1.0428 1.0869 1.1309 1.1751 1.2191 1.2629 1.3064 1.349 1.39 1.43 1.4685 1.5065 1.5253

Calculator :  http://www.handymath.com/cgi-bin/spcfgrv.cgi?submit=Entry


1% solution = 1.336 oz KOH added to 133.6 oz Water (1 gallon)
10% solution = 13.36 oz KOH added to 133.6 oz Water
28% solution = 37 oz KOH added to 133.6 oz Water
KOH amount = (1.336 oz) x (% you want to mix in 1 gallon of Water)




    Copyright 2003   All rights reserved.   Revised: 04/03/22.                                             Web Author, David Biggs
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