## fuel cells and volts

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### fuel cells and volts

For my experiment I am supposed to find the voltage produced from a fuel cell with different amount of table salt in the water. I just started to build a fuel cell according to sci-toys.com, and it works, but for some reason the voltage produced starts at 1.9 volts and eventually drops to a low voltage and spikes to higher one , not allowing me to get a steady reading. I don't know if i did something wrong or it is just like that.

Thanks for your help
technoaaron

Posts: 9
Joined: Tue Nov 27, 2012 10:06 pm
Occupation: Student: 9th grade
Project Question: Electrolyte Concentration's Effect on Fuel Cells
Project Due Date: December 1st
Project Status: I am conducting my experiment

### Re: fuel cells and volts

What are you using as a load? For DC power sources like fuel cells, both the voltage and the current can change with time, so measuring the "open circuit voltage" with a high impedance volt meter like most DVM's on a DC voltage scale doesn't adequately characterize the power source. If your meter has a DC current (AMP) scale that reads to more than the fuel cell's "short circuit current", you could also measure that property.

Another way is to utilize a resistor as a load. For example, having several 10 ohm 1/2 Watt resistors would allow you test with various loads.

BTW: Ohms Law calculations: 2 volts / 10 ohms = 0.2 Amps or 200 mA. 2 volts * 0.2 A = 0.4 W, so a 1/2 Watt resistor won't burn up.

If you put two 10 ohm resistors in parallel you get a load of 5 ohms. If you put two 10 ohm resistors in series, you get a 20 ohm resistor.

The power out of a fuel cell will be affected by chemical changes within the cell. In the case of the sci-toys.com platnum wire fuel cell experiment that I looked up, you don't have constant source of H2 and O2. The use of a 9 volt battery to break down the water and produce hydrogen and oxygen bubbles on the electrodes is the only source of H2 and O2.
-Craig
Craig_Bridge
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### Re: fuel cells and volts

Well i measured amps instead of volts, but i seem to get nothing.
technoaaron

Posts: 9
Joined: Tue Nov 27, 2012 10:06 pm
Occupation: Student: 9th grade
Project Question: Electrolyte Concentration's Effect on Fuel Cells
Project Due Date: December 1st
Project Status: I am conducting my experiment

### Re: fuel cells and volts

Hello technoaaron,

I looked at sci-toys.com but it's not clear what experiment description you are following. Would you provide a direct link?

I am puzzled that you say you read 1.9 volts out but zero current. Could you clarify how you connected the meter to read current? What did you provide for the current to flow through? Did you connect the meter directly across the cell output?

WW
wendellwiggins
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### Re: fuel cells and volts

Here's the link
http://scitoys.com/scitoys/scitoys/eche ... _cell.html

I connected the positive terminal of the fuel cell to an led and the led connected to the negative terminal.
i just measured the amps at the led at the + and - parts where it was connected to the wires from the fuel cell

I just want to get volt readings and amp readings fromm the fuel cell. Then I can experiment from there with electrolyte concentrations.
technoaaron

Posts: 9
Joined: Tue Nov 27, 2012 10:06 pm
Occupation: Student: 9th grade
Project Question: Electrolyte Concentration's Effect on Fuel Cells
Project Due Date: December 1st
Project Status: I am conducting my experiment

### Re: fuel cells and volts

technoaaron,

Here are a couple of reasons why you may observe no current,

1) I'm still not sure how you have the meter connected. I think you are saying that you have the meter leads connected to the LED leads. The meter should be in series with the LED. See the diagrams at http://www.electronics-radio.com/articles/test-methods/meters/how-to-measure-current.php.

2) The simple cell described at scitoys may not be able to generate enough current to light the LED. Also, some LEDs require a higher voltage than the 1.9v you mention.

Try just connecting the meter in current mode directly across the cell output. That measurement will tell you the maximum current you can get in any configuration.

WW
wendellwiggins
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### Re: fuel cells and volts

For my experiment, should i have an electrolyzer and fuel cell hooked up together with the same concentration and both run at the same time to get constant h2 and o2 and voltage?
technoaaron

Posts: 9
Joined: Tue Nov 27, 2012 10:06 pm
Occupation: Student: 9th grade
Project Question: Electrolyte Concentration's Effect on Fuel Cells
Project Due Date: December 1st
Project Status: I am conducting my experiment

### Re: fuel cells and volts

technoaaron,

I see no reason why you should use two different cells. After you run current through the cell to produce the hydrogen and oxygen bubbles, you have to switch quickly to observe the fuel-cell mode before the bubbles disappear. This requires that you switch a single cell from one mode to the other.

WW
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### Re: fuel cells and volts

Yea I just tested it with one cell and got .1 micro amps and 1.4 volts, although for the resistance, it had ol M omega why?
technoaaron

Posts: 9
Joined: Tue Nov 27, 2012 10:06 pm
Occupation: Student: 9th grade
Project Question: Electrolyte Concentration's Effect on Fuel Cells
Project Due Date: December 1st
Project Status: I am conducting my experiment

### Re: fuel cells and volts

technoaaron,

Good work.

The 1.4 volts seems reasonable, but 0.1 microamps seems too small to be read on most multimeters. Did you mean millamps?

The "ol" on the resistance reading means "overload." The cell doesn't have a fixed resistance because it is an active, current-generating device. Overload means that the cell generated enough current and voltage to appear as a resistance outside the capability of your meter.

WW
wendellwiggins
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### Re: fuel cells and volts

i have a question, if i want to measure amps, do i need a resistor because i got the amp reading from the previous reply without a resistor.
technoaaron

Posts: 9
Joined: Tue Nov 27, 2012 10:06 pm
Occupation: Student: 9th grade
Project Question: Electrolyte Concentration's Effect on Fuel Cells
Project Due Date: December 1st
Project Status: I am conducting my experiment

### Re: fuel cells and volts

technoaaron,

No resistor is required to measure current. You can simply hook the meter across the electrodes of the fuel cell. In its current-measuring mode the meter has a low resistance of its own.

WW
wendellwiggins
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### Re: fuel cells and volts

Do u think 20 minutes is good enough for recording data for my experiment?
thankS
technoaaron

Posts: 9
Joined: Tue Nov 27, 2012 10:06 pm
Occupation: Student: 9th grade
Project Question: Electrolyte Concentration's Effect on Fuel Cells
Project Due Date: December 1st
Project Status: I am conducting my experiment

### Re: fuel cells and volts

technoaaron,

I cannot say what length of time is correct for your experiment. You can determine the correct time of observation by watching how your readings change as you observe them. If you expect an observation to be constant, you need to watch it long enough to see that it remains constant.

I will guess that the output of your fuel cell decreases with time because the oxygen and hydrogen on the electrodes is being used up or the bubble are slowing coming off the electrodes. By watching the decrease over time you can determine how fast this happens.

Watching an experiment carefully is an important part of doing it well. Notice everything you can and let that data tell you when you have watched long enough. Another important technique is to repeat the experiment enough times to decide whether you are getting the same result each time. If you don't get the same result, can you figure out why?

WW
wendellwiggins
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### Re: fuel cells and volts

Quick question:
can a hoffmann apparatus be used to create electricity
technoaaron

Posts: 9
Joined: Tue Nov 27, 2012 10:06 pm
Occupation: Student: 9th grade
Project Question: Electrolyte Concentration's Effect on Fuel Cells
Project Due Date: December 1st
Project Status: I am conducting my experiment

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