How to make a Salt Water Battery Lamp.

Salt water battery + Joule thief circuit.

Materials : Copper plate, Aluminum Foil, Kitchen Towel, Warm Salt water, Joule thief circuit
Bigger copper plate & Aluminum Foil is more powerful.
This battery lamp turned on one hour.. but if you replace salt water, it will be lasting until the foil almost erode.

33 thoughts on “How to make a Salt Water Battery Lamp.

  1. Robert s

    Hi Thomas.Impressive work again. How long will light up led with this
    circuit? does C1815 transistor work with lower voltage then 0,7v on Joule
    Thief ? I wanna know if C1815 transistor works better on low voltage then
    BC337 or D965.

  2. Dave Myers

    I see a lot of people on the internet calling these things a salt water
    battery, but that’s actually a little misleading. The salt is just an
    ionic conductor– none of the power comes from it, and the salt is not
    depleted or used up ( the sodium and chloride don’t chemically react and
    don’t change at all). The cell “runs down” for other reasons, and if you
    cleaned the electrodes, stirred the solution, wrung out the paper towels
    and wetted them again with the stirred solution, it would perform just as
    before (assuming that the aluminum hadn’t all dissolved). All of the power
    comes from the oxidation of aluminum.

    At the aluminum electrode, the aluminum metal dissolves (oxidizes) and
    reacts with water to form aluminum hydroxide, and that also produces
    hydrogen ions and electrons:
    Al + 3 (H2O) –> Al(OH)3 + 3 H+ + 3 electrons
    At the copper electrode, water gets broken down to hydrogen molecules and
    hydroxide ions, and that also uses the electrons produced at the aluminum
    electrode.
    2 (H2O) + 2 electrons –> H2 + 2 OH- (that’s OH-minus, as in sodium
    hydroxide).
    (But before those electrons get to travel from the aluminum electrode all
    the way to the copper electrode, we use them to light an LED.)
    The H+ produced at the aluminum electrode and the OH- produced at the
    copper electrode eventually travel to where they can react with each other
    to produce water. So there’s never actually an excess of either H+ or OH-
    produced. One of the electrodes produces 3 electrons and the other one
    uses 2, so you have to multiply the first one by 2 and the second by 3 to
    get everything to balance, but after the dust settles (or the ions), here’s
    what has happened:
    6 (H2O) + 2Al –> 2 Al(OH)3 + 3H2
    See? The salt doesn’t appear. It doesn’t do anything except provide a path
    for all the ions to shuffle back & forth. What the salt does is allow the
    electrical circuit to be completed all the way around, but it doesn’t
    interact chemically.

    You also notice, the copper doesn’t do anything. That’s right. It only
    serves as an metal surface for the hydrogen gas to form on. For technical
    reasons it happens to be a pretty good choice, but other metals could be
    used to do the same thing and would give the same voltage in this cell as
    copper. Platinum, for example, although that’d be really expensive.

    Also, strictly speaking, it’s a cell and not a battery– if you hook up two
    or more cells in series (the copper electrode of each cell connected to the
    aluminum electrode of the next one) that’s called a battery. If you make a
    battery with 2 cells it will have twice the voltage as one cell; if you use
    3 cells it will have 3 times the voltage, etc.

  3. Dan Stroescu

    It seems interesting (educational, but also practical).
    How much time did the battery powered the LED (+ the oscillator)? I think
    the total power does not exceed 100 mW in this case. So I would like to
    appreciate the capacity (mAh).

    1. Dim Kit

      +Ciroluiro basically it comes from the difference in electronnegativity and
      work function of the two metals, and if you have no knowledge of physics
      would be hard to explain farther

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