You Can Turn Soft Drink Bottles Into Handy Solar Lamps

Solar lights are a popular garden decoration. Of course, they’re available cheaply from most hardware and garden stores, but if you’re more of the DIY type, you might like to build your own. [opengreenenergy] has done just that, using recycled materials for a cheap and simple design.

The design was inspired by the Moser bottle, which is a water-filled bottle used to diffuse sunlight into a room during the day. Instead of sunlight, however, this design uses an LED to provide the light, for decorating a garden or for use when out camping or traveling.

In this design, a solar panel is used to charge a lithium-polymer battery during the day using a LP4060B5F charge controller IC. It’s paired with a AP6685 battery protection IC to ensure the battery is not overly discharged or otherwise damaged in use. When the solar panel stops putting out power when it gets dark, the LED is automatically switched on. It can be set to a low or high brightness to provide more runtime or more light as needed.

All the circuitry is wrapped up in a neat 3D-printed case that allows the hardware to be screwed directly on top of a regular soft drink bottle. Paired with some water in the bottle, and perhaps a little bleach to stave off algal growth, the result is a handy, portable light that also has enough mass to avoid it being blown over easily.

It’s interesting to compare the design to commercial versions that aim to pare costs down to a minimum. Video after the break.


17 thoughts on “You Can Turn Soft Drink Bottles Into Handy Solar Lamps

  1. why use bleach? then you can use it to produce oxygen and color your lights green. 😅

    maybe add a drop of food coloring to change the color if ya dont like white or green?

    1. I’m not sure if it’s intentional or just error in the schematic but battery ground and circuit ground should be separate. The protection can then cut the ground connection between the battery and rest of the circuit in the event of undervoltage or overcurrent through a low side nmos.

      1. The point of having a bottle is to diffuse a point light source to light up an area much like a lantern would. No use just pointing a light up at the sky or only in one direction if the whole purpose is to light up an area 360 degrees around the light source.

        1. Yes, but if you’re trying with a phone LED, the best option is to hang the LED high up so it spreads the light around the area you want to light instead of wasting a third of the output on an inefficient diffuser.

          1. Also, the bottle won’t direct the light back down where it’s needed efficiently, so you’re actually losing something like 80% of the light – but you can see the ceiling more and have the illusion of lighting up the space at least.

  2. Finding that battery protection IC (the AP6685) is like finding hen’s teeth. Anyone have thoughts on something similar and more widely available? I’m looking at the AP9101C from Diodes, Inc.
    Also, there’s quite a bit of room for optimization in the 3d printed parts. The bottom part needs ~20mm of support material printed. I appreciate the work that went into getting the threads right, but 7 hours to print one bottom housing is challenging…

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