DIY Rechargeable D-Cell Battery From Aluminum Foil
Introduction: DIY Rechargeable D-Cell Battery From Aluminum Foil
There are plenty of tutorials online showing how to make homemade batteries. Sadly, most DIY batteries either have no practical use or come with a variety of hazards or complex demands. Lemon and potatoes batteries are generally incredibly weak and require perishable organic plant material as a starting point; home-brew lead-acid batteries are based on highly toxic and corrosive chemicals; and most other batteries types usually require strange chemicals like activated carbon or manganese dioxide. Well not this battery!
This battery is made from incredibly simple materials available in most homes and has enough power to run a variety of devices, especially when scaled up! This makes it an excellent emergency source of electricity when traditional batteries aren't available. Additionally, this design can be easily recharged with almost any direct current source, is remarkably lightweight, and, unlike the more common aluminum-air batteries, doesn't require airflow to run. So what are we waiting for? Let's get started!
Step 1: Gather the Supplies!
For this project, you will need the following items:
* Aluminum foil
* Salt (potassium, calcium, or sodium chloride will work, while bicarbonates, carbonates, and hydroxides won't)
* A source of a less reactive metal (tin cans or copper wire/tubing are both excellent options)
* Paper (writing paper, paper towel, and toilet paper are all viable materials)
* PVA glue (I'm using Gorilla wood glue)
* Water
These next few items are optional, but still recommended:
* 1" PVC pipe section (this will be the housing for the battery)
* Hot glue gun (for assembly)
* A multimeter (for testing)
Step 2: Design and Theory
All batteries are based on a type of chemical reaction known as a redox reaction (short for reduction-oxidation reaction). In a redox reaction, one substance is oxidized (loses an electron) while another is reduced (gains an electron). Pretty simple, right? It turns out when you separate this type of chemical reaction into two halves, you can channel the electrons that the substances exchange through a conductor and use them as electricity before they return and complete the redox reaction.
In this aluminum-metal battery, the two halves of the battery are soaked in a saline solution and separated by a special membrane that only allows sodium and chloride ions through. The aluminum on one half wants to be oxidized into solution as aluminum ions, while the copper or steel on the opposite side wants to remain out of solution as a pure metal. If the copper (or steel) side contains copper or iron ions in solution, the redox reaction will begin. The aluminum on one half of the cell will give up some of its electrons to go into solution, and the copper or steel on the other side will use up the electrons to convert the copper or iron ions in solution back into metallic copper or iron. 662
The membrane in between the two halves allows electrons and carrier ions like sodium and chlorine to flow and balance, while keeping the copper/iron electrons away from the metallic aluminum. If the copper or iron ions make contact with the aluminum, they will be directly reduced back into copper or iron metal, and no power will flow from the battery.
When the battery is charged, the positive terminal of the DC supply is connected to the anode and the negative to the cathode. As voltage is applied, chloride ions from the solution are attracted to the anode. The copper (or iron) reacts with the chloride ions to form copper or iron chlorides, which readily dissolve into solution. This effectively recharges the cell, making it ready for another electricity-producing redox reaction cycle. However, unlike the copper or iron which is rejuvenated upon recharging, the aluminum in solution at the cathode is far too reactive to revert back into aluminum metal when the battery is charged. Instead, it will be slowly corroded away into aluminum oxides and hydroxides (as well as sodium aluminate).
Step 3: Make the Anode
The anode will be the positive side of the battery, and must be made of some metal that is less electronegative than aluminum. Copper, iron, and steel are all good candidates, due to their high abundance, although copper seems to work the best. You may be tempted to use a less reactive metal like lead or silver, but they won't perform nearly as well due to the poor solubility of their chlorides. I personally used a short length of copper pipe that I wrapped into a cylindrical shape. In the images above, I also showed that an ordinary steel can may also be turned into a functional anode. Since this is meant to be a D-sized battery, I cut the anode material down to the height of an ordinary D-cell. 662