Ever wanted to make a battery but didn't have the time or the parts? Well here you go. You can literally make this in 5 minutes with only 4 parts. It is sealed and doesn't require chemicals... what more could you want!
Step 1: Parts and Tools
Not much is needed for this instructable, but you will need:
A film canister (or similar container)
Aluminium Foil
Tissue paper or kitchen roll
Carbon rod (Pencil led or battery rod)
Electrolyte (Salty water or other salt in water)
Some wire
Tape
As for tools,
Scissors
Multimeter if you want to check it.
A film canister (or similar container)
Aluminium Foil
Tissue paper or kitchen roll
Carbon rod (Pencil led or battery rod)
Electrolyte (Salty water or other salt in water)
Some wire
Tape
As for tools,
Scissors
Multimeter if you want to check it.
Step 2: Making the Cathode
The cathode is the negative terminal of the battery. For us, it is made of aluminium foil.
Start by cutting a strip of foil just slightly shorter than the film canister, but long enough to make a full ring inside with plenty of overlap.
Tape a wire to the foil so that it won't be facing inwards, but is against the side of the canister.
Try to curl the foil so that it will easily fit into the canister. Pulling it gently over a sharp edge does this nicely.
Insert it into the canister and leave it for now.
Start by cutting a strip of foil just slightly shorter than the film canister, but long enough to make a full ring inside with plenty of overlap.
Tape a wire to the foil so that it won't be facing inwards, but is against the side of the canister.
Try to curl the foil so that it will easily fit into the canister. Pulling it gently over a sharp edge does this nicely.
Insert it into the canister and leave it for now.
Step 3: Making the anode and electrolyte medium
The positive 'side' of our battery will consist of a carbon rod surrounded by electrolyte. The carbon rod is the hardest part to get right, as it needs to have large surface area and low resistance. I used the carbon rod from an old 'C' cell battery. Although I haven't tried it, a artist pencil led may also work.
The anode needs to be surrounded by electrolyte, which we achieve by saturating tissue paper with salty water. I use bicarbonate of soda in water, but any salt in water will do.
Start by taking two sheets of kitchen roll or other tissue paper and folding them into a narrow band slightly shorter than the film cannister. You may need to trim the height with a pair of scissors.
Now place the carbon rod along with a stripped wire end on one end of the paper. Roll the tissue paper as tightly and as neatly as you can.
On to the next step!
The anode needs to be surrounded by electrolyte, which we achieve by saturating tissue paper with salty water. I use bicarbonate of soda in water, but any salt in water will do.
Start by taking two sheets of kitchen roll or other tissue paper and folding them into a narrow band slightly shorter than the film cannister. You may need to trim the height with a pair of scissors.
Now place the carbon rod along with a stripped wire end on one end of the paper. Roll the tissue paper as tightly and as neatly as you can.
On to the next step!
Step 4: Filling the battery
Now we have to fill the battery. Start off mixing up some electrolyte. Keep adding salt to warm water until no more will dissolve. Keep stiring it and it will dissolve more.
Next we insert the tissue roll into the canister carefully, making sure the foil is straight around it and not creased.
Push it all in tightly, as the lid has to shut and seal the electrolyte in.
Now to fill the canister. Pour the electrolyte in slowly as it has to be absorbed into the tissue. when it begins to overflow, drain off the excess and wipe it down.
Next we insert the tissue roll into the canister carefully, making sure the foil is straight around it and not creased.
Push it all in tightly, as the lid has to shut and seal the electrolyte in.
Now to fill the canister. Pour the electrolyte in slowly as it has to be absorbed into the tissue. when it begins to overflow, drain off the excess and wipe it down.
Step 5: Seal the cannister
Now we just have to feed the two wires out the lid. Puncture two holes it the lid with the scissors and feed the wires through.
Pull the wires right through and clip the lid onto the canister fully.
Now all that is left is to test it!
Pull the wires right through and clip the lid onto the canister fully.
Now all that is left is to test it!
Step 6: Test the battery
The final step is to test it out. We need a multimeter to test the battery accurately, but if you want to check it works without a multimeter, just put the two wires on your tongue. If you feel a slight tingle that tastes metallic it works!
If you want to be precise, measure the voltage and current with your multimeter.
My battery produces between 0.8 and 1.1 volts at around 2-5mA. Using a joule thief you could run an LED from this. A larger surface area and stronger electrolyte concentration would improve the battery, but that is up to you to try...
Enjoy!
If you want to be precise, measure the voltage and current with your multimeter.
My battery produces between 0.8 and 1.1 volts at around 2-5mA. Using a joule thief you could run an LED from this. A larger surface area and stronger electrolyte concentration would improve the battery, but that is up to you to try...
Enjoy!
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Think of a battery as a perfect voltage source and a resistor connected together (and that can't be separated)- the resistor will limit the current that the battery can provide. A car battery can supply hundreds of amps so has a very small internal resistance, a coin cell has a high internal resistance so cannot provide a high current (which is how they can power LED throwies without burning out the LED).
The internal resistance defines how much power you can draw from a battery- in my example you couldn't power a car starter motor from 12V worth of coin cells, because they can't provide the hundreds of amps required, and I suspect your cell also has a high internal resistance.
More about the chemistry
I'm not sure how it deals with the oxide layer, I assume it either takes part in the reaction or is porous enough to allow the electrolyte to react with the pure Al underneath. Either way, the aluminium is supplying the energy.