DIY battery questions

Discussion in 'Homework Help' started by thematrixiam, Dec 16, 2011.

  1. thematrixiam

    Thread Starter New Member

    Dec 16, 2011
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    Hey guys,

    Warning - I am a complete Noob in this sort of thing

    I'm developing some information on electronics for my school project. I'm trying to get as much fun, and easy stuff as I can. I will probably need to know a little bit about what is going on, but really the knowledge does not need to be intensive as it's only at a grade 6 level. To clarify, I am not in grade 6. I am actually a university student doing my Bachelor of Education, and am working on this project for my science class. The project involves developing a resource that can be used to show kids some basic concepts about science or society. I choose electricity. In grade 6 students will look at simple things like how it can be created, parallel and series, etc.

    My main reason for posting here is to figure out what's going on with my initial testing. I have been looking up some info on building batteries by using differing metals in a liquid. But before I even tried that I was curious if I could get electricity while using similar metals and instead differing liquids.

    I started with lemon juice mixed with water in a glass, and water in another glass. I was able to generate 100 mV.

    I then tried milk to see if maybe this was in some way related to pH. I didn't really notice any large difference but was still able to generate electricity.

    My question is, is there any relation to the chemicals involved that can be used to create electricity in this way? Or am I just noticing the residual electrons/electrolytes moving around between the two chemicals to balance themselves out? Or something completely different?

    Also, if anyone has some good ideas, or directions they can lead me to basic electronics and working with energy it would be great.

    I am currently looking to see if I can build various home made electronic parts that would be simple to do. For example, a water bottle capacitor. And then figure out if I could put all of these things to use in a make-shift electrical circuit, to perform some sort of work. Ideally i'd be performing more work than lighting a light bulb. In an ideal world I'd be creating so much energy out of simple things that I could do something like run a DIY motor to power a DIY helicopter. Or something equally as cool. I'm trying my best to avoid the two electrodes in a lemon to light an LED as much as I can.
     
  2. thatoneguy

    AAC Fanatic!

    Feb 19, 2009
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    Your question relates more to chemistry than electronics.

    Look at the different metals and electrolytes are used in common batteries (e.g. Carbon/Zinc/Manganese) to get an idea of what you can do safely.
     
  3. thematrixiam

    Thread Starter New Member

    Dec 16, 2011
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    ya, I noticed a large difference when I added in a paper clip. it seemed the metal difference makes more difference than the actual liquid difference.

    Though having the differing metals in one liquid was interesting.
    The lemon water was the highest at 600mV
    but the milk was better than straight water with 460mV
    just water gave me 300 mV.

    I've been looking at leyden jars as well. Is there a way of converting stored energy from a leyden jar into usable energy? Wondering about combining some Kelvin Thunderstorms and Leyden Jars
     
  4. thatoneguy

    AAC Fanatic!

    Feb 19, 2009
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    Leyden jars are tiny capacitance, big ones being in the nF range, 1000 times short of uF range which is where most capacitors are used to store any amount of power. The pF/nF range is mostly used in tuned circuits/RF

    With your tests, write down the data using, say lemon juice, then try all the different conductors you have. It might be extra points to measure open voltage and voltage with a 100kΩ capacitor across the 'battery' to see what the voltage is when it is delivering a few microamp in current.

    Make sure your electrodes are polished clean, use a scotchbrite pad or similar.

    Then look up the different metals you used on the periodic table and see if you notice anything about the ones that work and don't work.
     
  5. KJ6EAD

    Senior Member

    Apr 30, 2011
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    You can find electromotive series charts on the internet to precisely predict the voltage you'll get using various electrode and electrolyte materials. I have one for normal saline solution for example.
     
  6. thatoneguy

    AAC Fanatic!

    Feb 19, 2009
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    You'll interrupt his learning! :eek: :D
     
  7. Georacer

    Moderator

    Nov 25, 2009
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    What age is the 6th grade, gentlemen?
     
  8. thematrixiam

    Thread Starter New Member

    Dec 16, 2011
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    haha. I'm actually not required to do any learning through trial and error. I'm just have to build a resource using what ever means necessary.

    Grade sixes are about 10-12 years old.

    They won't be required to know periodic tables, molecular charges, etc. But they are required to have some basic understandings about matter. For example, in grade 2 students need to know

    Just by going with that I could show how different liquids and solids can be used to create energy.

    Grade three is about forces that cause movement. 4 is light and sound. 5 is the change of matter, and the use of that change. Grade 5 also have part of the earth systems section that deals with conservation of energy and resources. grade 6 deals with useing air for various purposes, and a whole whack of stuff on electricity.

    here's what grade 6 has:

    I think I could easily use the things I'm trying to create to teach how this works to kids. But the level at which it works they wouldn't need to know. They'd need to know enough to get a basic grasp about what's going on, and not to kill themselves if they ever try to repeat it.
     
  9. thematrixiam

    Thread Starter New Member

    Dec 16, 2011
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    in terms of electrodes, I think the simplest thing to get on hand would be nails(zinc) and copper. What do you guys think?

    zinc is listed as -.76
    while copper has several listings ranging from +.159 up to +.52

    I have a feeling getting some flourine and lithium would be kinda hard.
     
  10. MrChips

    Moderator

    Oct 2, 2009
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    Before you can teach a Grade 6, you ought to know a bit more than a grade 6 level. Which means that you need to know about chemistry, the electrochemical series and electrolytes.

    You also need to know how much energy it takes to light an LED. You are no where close to powering an LED much less a DIY helicopter.
     
  11. thematrixiam

    Thread Starter New Member

    Dec 16, 2011
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    Yep. That's what I am working on figuring out right now.

    I was able to power a 3v bulb, not an LED, with a magnet generator so far. As per using what I have already done, I can increase the power through series and parallels.

    Does anyone know of low voltage capacitors? I noticed that you can actually build up voltage by linking people together as well. Wonder if there's any sort of application I could get out of that.
     
  12. thematrixiam

    Thread Starter New Member

    Dec 16, 2011
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    where can I find info about the liquids i need to work with for different metals. for example silver
     
  13. Adjuster

    Well-Known Member

    Dec 26, 2010
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    The web is full of stuff about basic electrochemistry. You will need to be patient, and do some reading. Resources aimed at for students of around the age you are teaching or a little older might be about right. Here is a list of potentials for metals http://www.efunda.com/materials/corrosion/electrochem_list.cfm?sort=com

    You will not be able to obtain much current, unless you want to use electrolytes at least as nasty as those used in real batteries, coupled with reagents to deal with gas at the positive electrodes which will otherwise cause the cell to run out of steam pretty fast.

    http://en.wikipedia.org/wiki/Lemon_battery

    At around the age you are talking about I did manage to get enough juice to run a small radio from a home-made battery, but this involved several large glass jars full of lavatory de-scaler, a hazardous and smelly experiment which I'm sure you would not want your little "charges" to imitate.

    Typically, on a reasonable scale this sort of project can just about run an LED, perhaps by using a circuit called a "joule thief" to increase the cell voltage. http://www.bigclive.com/joule.ht (A simple circuit, but people with little experience often have difficulty with it.)

    Without some means of stepping up the voltage, several cells will be needed to light even a low-voltage red LED. Good LEDs will give a weak but visible light with less than a milliamp (a thousandth part of an ampere).

    Capacitors will not get you any more power averaged over a given time, but they can be used to store up charge and allow brief bursts of higher current. This might allow you to get brief brighter flashes of light, compared to a steady glimmer. This might be done in conjunction with a circuit called a "CMOS 555", but this may be too complicated for you.

    Another fairly popular load for a home-made battery is the LCD type of digital clock. These use very little current indeed. Try googling "lemon clock" You might even treat yourself to one of the many kits sold as educational toys: they do vary in quality, but a good one might give you the chance to try this out for yourself. Example: http://www.hometrainingtools.com/enviro-battery-kit/p/KT-GSENBAT/
     
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