Solar Battery Charger and Flashlight - Made From Recycled Junk!

Our Planet is a precious and scarce place in the vast universe. We are so lucky to live on a planet that is perfect for us. The nearest planet to have the same conditions is trillions of miles away.

But in the past 100 years, we've been using up our planet's resources at an astronomically high rate, significantly faster than we should be. We've also been causing severe pollution and waste. One of the most common things we throw away is batteries.

It's estimated that 600 million batteries have been thrown in the trash in the UK per year alone, despite us being able to recycle them and use them again. Can you imagine how many a thrown out worldwide? However, rechargeable batteries becoming increasingly common, as they can be recharged hundreds of times. Despite this, they still require energy to charge, often generated from coal and oil power plants. Solar battery chargers seem to be very rare. As a DIY enthusiast, this brought up a few ideas...

So I designed this tiny but mighty project: A simple solar battery charger. Almost completely built out of recycled parts and materials. The design is super simple to build, but it works very well. Two AA batteries will charge in a few hours. Here's how it works.

The solar panel charges the batteries when the power switch is flicked on. As a bonus, the circuit includes a bright LED that can be turned on and off! It's perfect for putting beside your bed when not in use.

It may be small, but it's important to remember that every step counts. Imagine how much waste and pollution we could reduce if we simply used rechargeables and charged up with Solar Chargers. I've designed this to be as simple as possible, because I've always followed this ideology: it doesn't need to be complicated to work.

Let's get building!

As a bonus, I designed this almost completely out of reused parts from broken electronics. These items would go to a landfill otherwise. Some aspects of this project, like hot glue, were not able to be sourced from broken electronics. However, I encourage you to look for these products in a recycled form! I'm using this build as an AAA battery charger, but you can also use AA batteries.

Part 1: Circuitry

• x1 AA/AAA battery holder - I recycled mine from old school tech supplies going to be thrown out
• x2 Toggle Switch or Rocker Switch- Found in a broken toy
• DuPont Wires - from former students' DIY projects
• Rechargeable AA/AAA batteries
• x1 3V Solar Panel (see step 2 for more details)
• 3V LED (I used an LED from old outdoor lights)

Part 2: Recycled Wood

• Scrap MDF and Plywood - rescued from a scrap wood giveaway, otherwise going to the landfill. You don't need a ton of it!
• Small 2x2 wood block (for the solar panel to sit on)

Part 3: Tools

• Solder Iron and Wire (optional)
• Drill with Square Bit
• Hot Glue Gun and Glue
• Circular Saw
• Multimeter

Some places to find Switches, Solar Panels and Battery Holders:

• Garden Lights (this is where I found my solar panel)
• Broken Toys (use battery holders in them)
• Broken School Tech Supplies (my teachers were happy to give me broken equipment from the tech room)

Planning this project, I decided to make diagrams of this project on-paper as a rough draft. However, I wanted a clear, 3D design of this. So I used Fusion 360 and made a 3D model. I decided not to include any 3D printed elements in this project, as it creates unnessecary waste. We don't want that!

Unfortunately, I don't have the model available. Why? Well, I may or may not have forgot to save my progress on fusion 360. So I literally lost my hour of work. Oops. But that's part of DIY. We make mistakes and learn from them. So while I can't provide my model due to time constraints to make another, I hope this can serve as a reminder to SAVE YOUR WORK.

In order to meet my goal of crafting a green piece of tech, I designed this project under THREE enviromentally-friendly criteria listed by the Instructables Team:

• Design an object to reduce the amount of material required for manufacturing. (reduce battery consumption, simple project)
• Develop a clean energy solution. (using solar panel, completely renewable)
• Recycle materials from discarded objects. (built almost completely out of discarded trash)

My Design: Single-Panel Power

I was lucky enough to come across a broken garden light with a large solar panel. As such, I would only need one to have enough current to charge the battery. From the info I found online, this was a 3V panel that outputs a maximum current of 400mah. It's not a ton of current, but it's enough to charge up in a few hours. Make sure to use a multimeter to test this panel while in sunlight, ensuring the voltage and amperage remain at 3V and under 700mah, respectively.

Cut out The Base:

Simply cut out your plywood to a dimension of 125mm by 85mm. I used a circular saw.

Cut out Solar Panel Base:

First, I measured a piece of scrap MDF to the size of my solar panel. This was cut out with a circular saw. All solar panels are different, so I leave this up to you.

Next, I grabbed my solar panel and soldered two wires to the positive and negative terminals. I used red and black wires to distinguish the positive and negative terminals easily.

Finally, I hot-glued the panel to the MDF, making sure the wires went to the same side as shown.

To build the frame, follow these steps:

First, measure out a few important things on your piece of plywood. The battery case, breadboard and wood block must be measured and marked with a pencil. Use this diagram. Since these components vary in size, your results may differ.

Now, glue down your wood block. This will act as the stand for the solar panel.

Now Glue down the terminal piece. It must be disconnected from the rest of the breadboard.

Glue down your battery case. Take the batteries out before doing this.

Set the solar panel against the wood block, with the wires facing the top. Glue the panel down.

Finally, Hot-glue your LED to the backside of the frame.

Since I was using a breadboard, I didn't need to solder anything. This is good, because I don't have a solder iron, and honestly, I'm afraid I'm gonna burn myself 😂

To start, glue your two toggle switches to the long side of the board. Doesn't matter which side, though I used the side shown below. In the following pictures, you may see blue dots marking important wires. This is to reduce confusion, if neccesary.

First, connect the Positive Terminal of the solar panel to the first switch. Next, connect the other side of the switch to the breadboard's positive. Connect the negative of the solar panel to the negative terminal on the breadboard. This switch has now been wired, and it is used to control the flow of current from the solar panel to the battery, which is important to the battery not overcharging. It should also be flicked off even inside, as current can leak back out into the solar panel. For now, flick the switch off.

Connect the positive battery terminal to the positive of the breadboard. Connect the negative battery terminal to the negative of the breadboard. We now have a functional charger, however we still have to add the LED.

You may also want to hot-glue some of your wires in place.

Connect the first wire on the switch to the positive on the breadboard. Connect the other side of the switch to the positive on the light.

Connect the Negative of the breadboard to the negative on the LED. You have fully wired your solar charger and LED.

First, fully drain your batteries. Also, use a multimeter to test the current and voltage of your circuit, making sure that power is actively reaching your batteries.

Now, plug in your batteries and position your solar panel towards the sun. Depending on your solar panels and batteries, it will take about 3-5 hrs to charge up. Make sure your batteries are covered in some way from the sun - exposure can lead to damaging the battery! It is recommended that you don't over-charge the batteries, as there is no over-charge protection. Calculate how long your batteries need to charge. (battery capacity ÷ solar panel current = charge time in hours)

Once Charged, flick the switch to turn the solar panel charging off. Flick the second switch to send the power from the batteries to the light. If all goes correctly, you'll be getting power!

From here, you can use your batteries in anything that accepts them. You can also keep them in the charger and use the light!

I've really enjoyed building the project. However, next time, I would like to build a circuit with overcharge and overvoltage protection. Feel free to make your own version of this!

This project has been super useful to me. I'm happy I was able to reuse old parts to make an enviromentally-friendly alternative to regular batteries. Building this made me remember that we have a loooong way to go before climate change is fixed. However, it's the small actions that matter the most.

Thank you for reading and building! Together, let's create a cleaner future...