DIY Rechargeable Battery, Positive (+) electrode is Copper from electrical wire and Negative (-) electrode is Aluminium from aluminium foil, the Electrolyte is concentrated Saltwater.

Salt water battery generates 0.5 Volt per cell with only 4 ma of current but after i charge this battery it gives 1.4 Volt and up to 800 ma even though the electrodes are very small.

Chapters:
0:00 Building the Battery Electrodes
2:16 Toilet Paper Separator
6:45 Salt Water
8:39 Battery Voltage Before Charge
9:30 Charging the Battery
10:48 Battery Voltage After Charge
12:32 Battery Current

When u charge it for the first time the Copper wire Oxidises into Copper hydroxide and held separate by the paper seprator from reacting with the aluminium, then when you try to discharge the circuit by connecting a load or wire externaly from aluminium to copper electrode, because cupper has higher electronegativity than aluminium it will pull electrones from aluminium through the wire, and inside the battery a reaction starts happening between aluminium and the copper hydroxide, which normaly will happen if they contact physicaly and exchange electrones, but here we have seperated copper hydroxide and aluminium using a paper seperator and their solutions can't mix, but the external wire and the difference in electronegativity help the electrones to move from Aluminium to the Copper Hydroxide externaly and inside the cell aluminium turns into ions and the copper electroplates back onto the copper electrode. Hydroxide ions will pass the through the pourus memberane (paper) and will react with aluminium.

Charging: Cu + H2O - 2e = Cu2+ 2OH-
Discharge: 3Cu2+ +6e = Cu and 2Al -6e = 2Al3+

Because of the high potential difference between H and Al, water-based plating chemistries cannot be used for aluminum electrodeposition. Aluminum electroplating uses a solvent-based chemistry to overcome the electrochemical barriers to plating with an aqueous electrolyte.
As you see we lose the aluminium permanently and it is cheap and can be replaced, need a lock and seal mechanism to change the Aluminium electrode when its used up. or we can just sell this as a one time use battery where u only charge it for a single use.
Electronegativity is a chemical property that describes the tendency of an atom or a functional group to attract electrons toward itself.

High current 800ma 3v diy salt water battery, 800 ma is a lot of current from that little bit of material used, a piece of copper wire, aluminium foil, salt, water, paper.
how to make rechargeable battery

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