Question about Batteries

[hcarts]

( Series Circuit)

Hello!
As you can see in the above photo, I am making/planning a series circuit of aluminum can batteries. The copper sheeting inside (second photo) is the anode and the aluminum can is the cathode. My question is, I will connect the negative to positive terminals (series ) from one can to another using a copper wire. Will this affect the current? Because, as I have read, the aluminum and copper in my battery should not touch but the copper wire will be touching the aluminum can. I don't know about all of this so please help me.

 

[davenn]

hi hcarts
welcome to the forums

your statement on your lower diagram about more voltage more current is not an accurate one

for example say your 16 cells in the top diagram are 1V each then, you have 16V at a given current capability when they are in series as shown.
If instead, you parallel all 16 cells then you have 1V at 16 x the current capability

Dave

 

[hcarts]

hi hcarts
welcome to the forums

your statement on your lower diagram about more voltage more current is not an accurate one

for example say your 16 cells in the top diagram are 1V each then, you have 16V at a given current capability when they are in series as shown.
If instead, you parallel all 16 cells then you have 1V at 16 x the current capability

Dave

Thanks Dave
I understand that part. Thank you for clarifying that. Umm.. But can you answer this question I posted above?
I am making/planning a series circuit of aluminum can batteries. The copper sheeting inside (second photo) is the anode and the aluminum can is the cathode. My question is, I will connect the negative to positive terminals (series ) from one can to another using a copper wire. Will this affect the current? Because, as I have read, the aluminum and copper in my battery should not touch but the copper wire will be touching the aluminum can.

 

[Harald Kapp]

You have to differentiate between alu/copper within the electrolytic cell (aka battery) and the alu/copper connection outside of the cell.
If the alu touches copper within the cell, this short circuits the cell and the cell voltage will drop to 0V. So in this repect, as you correctly stated, alu shall never touch copper.
Outside of the cell there is no electrolytic process, so no voltage generated. Therefore you can use and conductive material to connect two cells. That includes copper.

Harald

P.S.: To be exact: any combination of different materials will generate a very small voltage on the order of millivolts (see http://en.wikipedia.org/wiki/Thermocouple), but this is usually neglected in applications like your's.

 

[hcarts]

You have to differentiate between alu/copper within the electrolytic cell (aka battery) and the alu/copper connection outside of the cell.
If the alu touches copper within the cell, this short circuits the cell and the cell voltage will drop to 0V. So in this repect, as you correctly stated, alu shall never touch copper.
Outside of the cell there is no electrolytic process, so no voltage generated. Therefore you can use and conductive material to connect two cells. That includes copper.

Harald

P.S.: To be exact: any combination of different materials will generate a very small voltage on the order of millivolts (see http://en.wikipedia.org/wiki/Thermocouple), but this is usually neglected in applications like your's.

Thanks Harald

Now it is all clear to me. I have been pondering on that thought for a long time now.
I have another question though, if you don't mind. It's just that I would like to know what two metals would create the highest voltage if placed in an electrochemical cell. Also, does the distance of the two metals create a significant difference. For example, what if they were closer? I know there are limits, so to what extent or distance can I put them away from each other (minimum and maximum)?

If you have an idea, please tell me. This is for my science fair project. I'm 14

 

[Harald Kapp]

The cell voltage depends on the difference of the "standard electrode potential" of the two metals. See here http://hyperphysics.phy-astr.gsu.edu/HBASE/Chemical/electrochem.html#c1 or in the wikipedia.

The distance between the metals plays a role insofar as (in general) the electrolyte conducts electric current not as good as a metal. Therefore it poses a resistance to the current.
As long as the cell is unloaded (no current), you won't see a difference. The cell voltage will be the same if the electrodes are spaced close or far apart. If you load the cell (draw power from it), then the voltage of the cell with electrodes spaced far apart will drop significantly.
You can observe this effect with commercial cells (e.g. AA alkaline battery) when its power has mostly expired. Measure the voltage of the unloaded cell with a voltmeter and you will still find a reading near 1.3V-1.5V. Add a load (e.g. a lamp) and the voltage will drop below 1V.

The minimum distance is practically given by the requirements
1) the electrolyte must fit between the two electrodes
2) the two electrodes may not touch
plus a certain add on for safety (remember that the electrodes will move due to movement of the cell, thermal expansion or contraction etc. Commercially a separator (see http://en.wikipedia.org/wiki/Alkaline_battery) is used to keep the electrodes at distance. You might try a sheet of blotting paper.

The maximum distance is given by
1) the size of the cell
2) the resistance of the electrolyte

Oh, and by the way: water alone is not a good electrolyte for your cells as it is barely electrically conducting. You'll need an additive, typically an acidic one. A simple, inexpensive and not dangerous additive is plain table salt.


Harald

 

[(*steve*)]

If I were you, I would experiment with distance. Find out for yourself if it matters.

This is science. Don't ask for what will happen, experiment!

Saying "Some random bloke on the internet said I should put them exactly 5.44mm apart" is less convincing that doing experiments that show variation in (say) voltage, current, or capacity based on some variable (say distance between electrodes).

I can tell you there WILL be an effect, but it may be swamped by other variables.

The experiment isn't hard to do. Set up a tank full of your electrolyte and insert an anode and cathode (say) an inch apart. Measure the open circuit voltage and short circuit current. Note these values (distance, voltage, current). Now move them so they're 2 inches apart. Repeat your measurements. Keep going until you run out of room. Maybe you can try less than an inch too.

Note that you should ensure that you placed the electrodes as close as possible to the same depth in the electrolyte each time.

Once you've dome the experiment, graph the results, Do you see any pattern?

Can you explain the pattern? Can you make a prediction based on your results? Can you test that prediction?

Now you're doing REAL science.

In answer to your other question, you should look up "Electronegativity". The difference in electronegativity is what drives a simple primary cell.

An old technologu is carbon/zinc. Perhaps you should try to get a piece of Zinc and a carbon rod and use them as comparison electrodes. How does your pair of electrodes compare? What about your electrodes in combination with carbon or Zinc? What is the voltage? Which electrode is negative? Is there a pattern? Can you make a prediction? Can you test that prediction?

More science!!!!

 

[hcarts]

The cell voltage depends on the difference of the "standard electrode potential" of the two metals. See here http://hyperphysics.phy-astr.gsu.edu/HBASE/Chemical/electrochem.html#c1 or in the wikipedia.

The distance between the metals plays a role insofar as (in general) the electrolyte conducts electric current not as good as a metal. Therefore it poses a resistance to the current.
As long as the cell is unloaded (no current), you won't see a difference. The cell voltage will be the same if the electrodes are spaced close or far apart. If you load the cell (draw power from it), then the voltage of the cell with electrodes spaced far apart will drop significantly.
You can observe this effect with commercial cells (e.g. AA alkaline battery) when its power has mostly expired. Measure the voltage of the unloaded cell with a voltmeter and you will still find a reading near 1.3V-1.5V. Add a load (e.g. a lamp) and the voltage will drop below 1V.

The minimum distance is practically given by the requirements
1) the electrolyte must fit between the two electrodes
2) the two electrodes may not touch
plus a certain add on for safety (remember that the electrodes will move due to movement of the cell, thermal expansion or contraction etc. Commercially a separator (see http://en.wikipedia.org/wiki/Alkaline_battery) is used to keep the electrodes at distance. You might try a sheet of blotting paper.

The maximum distance is given by
1) the size of the cell
2) the resistance of the electrolyte

Oh, and by the way: water alone is not a good electrolyte for your cells as it is barely electrically conducting. You'll need an additive, typically an acidic one. A simple, inexpensive and not dangerous additive is plain table salt.


Harald

Thank you so much! This was the information I needed.
Oh and yeah, I am not using water alone as an electrolyte, I prepared a fermented solution that could deliver a 2 volts current. This will then hooked up to an inverter and you know what's next....
I am really so grateful for your help. Now I can conduct my study.
Damn. Guys here are so smart

 

[JMW]

Also look up reactivity of metals. For zinc, you can use a galvanized nail or screw. It will work until the plating wears off. As for gold and silver, I suggest you refrain from using Mom's wedding ring or the family silver.