Working Air Battery

[Pirate88179]

I have difficulties to find references on internet about carbon + magnesium battery.
I don't know why, because it's the higher voltage I can get from basic material.
I compared iron, copper, aluminum, magnesium, each with each
The magnesium + carbon/graphite gives FAR MUCH HIGHER voltage than any other combination !!

Magnesium is largely used and available as is carbon. Why not much data on this on the web !?

Here is a chart of the potential of metals in water:

http://www.thelenchannel.com/1galv.php

We found that magnesium and carbon were the easiest to get that had the largest potential difference.  We learned this on the earth battery topic a few years back.  There are some other metals that can be explored but, I think this combination is the best all around for the average person.

I think Lasersaber's work here has opened up many more possibilities for practical designs and uses.  I am looking forward to seeing what he has come up with now.  This is a very interesting field of study to be sure.

Bill

[stephenafreter]

Thanks Pirate for this chart ! Very useful indeed !
Graphite is at one end, and on the other extreme side, to get the largest potential difference, we have :

- lithium, but it's expensive

- potassium but we can't use it pure with water : Quote from Wikipedia : "Elemental potassium is a soft silvery-white metallic alkali metal that oxidizes rapidly in air and is very reactive with water, generating sufficient heat to ignite the evolved hydrogen." End quote

- then sodium, also very dangerous pure : Quote from Wikipedia :"Elemental sodium does not occur naturally on Earth, because it quickly oxidizes in air and is violently reactive with water, so it must be stored in an inert medium, such as a liquid hydrocarbon."

- and then our magnesium, very abundant, very cheap and easy to manipulate like in this alloy ribbon. Of course pure it would be also very reactive.

Amazing how the other elements have much lower potentials !!
Even carbon has almost 3 times less potential than graphite, that explains why the carbon fiber works but with lower results than the carbon/graphite pencil ...

Very useful link again Pirate, thanks for sharing 

[conradelektro]

I did some tests with mild steel and copper in saltwater (see the two attached photos):

The steel - salt water â€" copper cell:

- Glass jar, diameter 100 mm, height 130 mm, contains about 1.1 Liter saltwater

- Salt water: 1.1 Liter tap water with 50 grams of table salt (about seawater salt content, more salt does not help)

- Steel sheet from old stove pipe, scrapped blank, about 120 cm2 (about 18 square inches), bent into a tube with 55 mm diameter and 70 mm height

- Cotton cloth wound in three layers around the steel tube

- About 4 meters copper wire wound on the cotton covered steel tube

- Masking tape wound over the copper wire to hold it tightly to the cotton covered steel tube

- About 0.41 Volt initially


Results:

- very similar to my tests with aluminium and copper in saltwater, the steel - copper cell worked very well for some minutes (up to 10 mA), then it gave about 1 mA for several hours, but finally Voltage dropped rapidly and also Amperage diminished

- removing the cell from the salt water and letting it dry out revived the cell for several houres (about 0.5 ma at up to 0.4 Volt, later about 0.3 Volt), but also this stopped because the steel was completely covered in rust


Further plans:

- it seems that "aluminium - copper" and "mild steel - copper" initially after putting it in salt water (or water with citric acid) works very well, but stops functioning after a few hours (this can be repeated by putting in "fresh" salt water, but I do not know what element was used up, I suspect it is oxygen)

- a design like Lasersaber's air battery (a ribbon wound over a wet paper towel covered core) seems to work longer and more reliably (as I see from various posts)

- the question is, "how wet should the paper be?"; Lasersaber wants a very dry paper for his magnesium - carbon cell

- therefore I will build some cells with a ribbon or wire wound over a wet paper covered core, because proximity of the two metals also helps

- I bought a stainless steel sheet, copper pipe, aluminium pipe and aluminium sheet and will carry out tests also with copper wire and aluminium wire and will post the results


Update on the aluminum - tile cement - copper cell

- my "aluminium - tile cement - copper cell" (driving a JT with one red LED now for a month) likes some moisture (best from humid air); "completely dry" stops it, also "very wet stops" it

- after dipping the cell in water it takes up to two hours (till the moisture is not visible any more) to function as usual (1 - 1.1 Volt without load, about 0.3 mA continuously)

- depending on air humidity the cell has to be dipped in water (for a few seconds) after a few days; the longest run was 7 days without a water dip (in very rainy weather), the shortest run was 3 days (windy dry weather)


Greetings, Conrad

Remark: it is important to put some load on a cell when testing; Voltage can look very good for a long time, but Amperage usually drops fast or is very small from the beginning

[PeteIdl4]

Further plans:

- it seems that "aluminium - copper" and "mild steel - copper" initially after putting it in salt water (or water with citric acid) works very well, but stops functioning after a few hours (this can be repeated by putting in "fresh" salt water, but I do not know what element was used up, I suspect it is oxygen)

- a design like Lasersaber's air battery (a ribbon wound over a wet paper towel covered core) seems to work longer and more reliably (as I see from various posts)

- the question is, "how wet should the paper be?"; Lasersaber wants a very dry paper for his magnesium - carbon cell

- therefore I will build some cells with a ribbon or wire wound over a wet paper covered core, because proximity of the two metals also helps

Nice work Conrad,

To your first point, I'm inclined to agree that a fresh supply of oxygen is a key component to these type of batteries. I made a few aluminum and copper wire cells that have been running a JT and a white LED for 4 consecutive days. No added water than what I initially started them with. Each cell has been giving an average of 7-8mA at a little over half a volt. I recently made another as a video tutorial(I will post the links at the bottom of the post) so I am now going to start a long term test on all three.

As for lasersaber's air battery I believe he wants as little moisture as possible to prolong the life of the magnesium and his latest design seems to be holding up very well, but as for these cells that use aluminum I think we should be okay with a little more moisture than what the magnesium air batteries can handle. I also totally agree that proximity is a big factor. Lastly great job on your cement tile cell I like the continued progress, keep up the good work and thanks for sharing your results.

Tutorial video on my aluminum and copper cell:
Part 1 http://www.youtube.com/watch?v=B9YqFY-Z0dk
Part 2 http://www.youtube.com/watch?v=ZeQof7ue9xA

[conradelektro]

@ Pete(Idl4) - nice videos and your design is a very good idea -the aluminum from the cans and the copper wire are used very cleverly

I will try to copy your "aluminum sheet - salt water paper - copper wire" cell as closely as possible. Long time tests are crucial.

Remarks:

- the output of about 8 mA is very impressive; this probably comes from the clever use of four aluminum surfaces in your design

- "copper wire turns should not touch": air should be able to pass through the windings and galvanic action should happen all around the copper wire (more surface), but electrically I do not see a significance (further tests should clear that up)

- "moist but not wet paper": the paper should have some moisture but air should be able to flow through (which seems to be the problem with my wet cells)

- "air flow": all comes back to air being able to enter the cell and touch one of the metals, I think it is aluminum which needs the air (oxygen); as long as the cells is porous to air any lack of oxygen will be equalized by the surrounding air

- one has to think about a design that allows easy adding of moisture every now and then, a trade off between "air flow" and "not drying out to fast"

- Lasersaber had the idea, that salt crystals will absorb just enough moisture from the surrounding air, therefore he soaked the paper (or cloth) in saturated saltwater and waited till it was almost dry (as far as I understood) and I will try the same

- "masking tape": if the salt crystal idea is correct, one should use cotton string to hold the cell together because it will allow better air flow; air should be allowed to enter from both ends of the cell and also from one side (do not overlap the outer aluminum sheet on one side)

So far my conclusions from the great ideas I see in this thread, greetings, Conrad