Satellite Solar Charger

We are going to build a functional satellite model!

This build combines the two mini solar panels, a battery (needed for storage, and decent charging speed), and a circuit board, into a very usable sustainable power source in style.
It's easy to build, costs only about 20$ with all new parts, and will give you some free energy!

To buy:

1. Solar panels: ~10$ (for 5)
   Sunyima 6V 1W 132*48Mm
   (other 5.5V or 6V rated solar panels will also work, but need a custom 3d printed holder)

2. Any 18650 battery: ~6$ (with a minimum lower than 2.9V - and a maximum at 4.2V)
   For example Samsung cell

3. Circuit Board: ~4$
   Circuit Board - Lilygo T-Bat for 18650 (CN3065 chip)

Additionally:

• Soldering tools
• Electrical tape
• Glue (I use hot glue) / Gum / Dubbel-sided tape
• 3D printer
• Silver spray paint (silver-tape sticker will also work)
• Wire
• A small screwdriver

Before we start, I want to make clear there are several risks involved. There are a lot of people making DIY power banks and most of the time no problems will occur. But if you start this build without knowing some of the basic electronics/ battery cell knowledge, I advise you to first look into the potential dangers to avoid serious hazards.

Since this build uses a Lithium-ion battery, there is a potential risk of fire hazard. The board used has a protection system that should protect the battery from under-voltage or overvoltage, and protects against shorts. This takes away a large portion of the potential risk.

Still, by wiring up the solar panels in the wrong way, using a wrong type of battery, or making another mistake, the lithium cell can be potentially dangerous. It is therefore wise to only start this build if you know basic electronics and know the dangers of lithium cells. Still, it is good practice to always test voltages, make sure not to leave the device unattended, and do some test runs.

Additionally, the charger can be a potential danger to the devices you want to charge. The used board has a protection system, but a malfunction could still lead to a larger voltage being applied at the device.

The first step is to solder wires to the solar panels.
The plus and minus are assigned with little stickers, color-code your wires for extra safety.

After soldering make sure to add a lot of tape, the connections should never be able to touch. I even added a small dot of hot glue to the end, this acts as a little strain relief for the brittle solder connections.

Afterwards, cut the wires to a length of about 7 cm (quite long, but this makes it easier to assemble).
Strip the end to about 5mm, this will is used for the connection to the board.

Now the solar panels can be connected to the board. Make sure to retest polarity first, otherwise the board can be damaged!

If the polarity is good for both panels, we can add them to the board. First open up the screw terminals by twisting them with the small screwdriver. Start by adding either both red "+" wires or both black "-" wires together in the solar input. After tightening the screw, make sure to pull on both wires so you can test if they are connected strongly.

Repeat this for the other two wires. Now your electrical circuit is almost done!

Start again by testing the polarity of the battery. Add markings ( + and - ) right away. This makes sure you correctly remember the polarity.

Now for the easiest step, check the markings on the PCB of the board. (Always check the PCB, the holder also has markings but is sometimes placed on mirrored). Push the battery in, and you're done with the electrical part of the build!

After 3D printing the body parts, I am going to spraypaint them with silver spray to get more of a satellite look. Since the printed quality is quite rough, the first step is to sand the body parts on the outside.
First I used sandpaper:120, afterwards sandpaper:600 to make it smooth. After spraypainting and letting the parts dry, the shiny silver look is done!

Other options to do this are:

• Using aluminium tape / silver-coloured tape
• Using foil (for example aluminium foil) (but do be careful not to come close to any wires, as aluminium foil is conductive and might short the circuit.

Now it is time to add the solar panel mounts. These mounts fit on the lower body half. I used hot glue to glue them together. First a bit on the lower half, then once the panel was pressed over it, a bit over the top.

By placing the satellite faced down, you can ensure the panels to dry up at the correct angle.

Because my glueing skills are a bit messy, I had to remove some of the glue afterwards. The top half would not fit over.

To finalize the satellite the mechanical and electrical parts have to be attached. You could glue them together. Since I wanted to be able to remove components, I decided to use poster gum. By applying it at all the places in in the photo, the electrical parts were attached sufficiently, but still a little less robust than using glue.

Finally the top cover can be pressed over the board, aaand the satellite is done!

• Note: I tested various devices. In order to safely test, I started with an Arduino. which ran perfectly fine on the satellite. Also a powerbank which I had lying around started charging when connected. It did however not work for my phone, which is an Iphone. After doing some minor research online I found this could be due to the requirement an additional pin to be high.
• Note: With regard to the solar power generation, I still have to test the exact performance. The past few days have been very clowded. The solar panels do generate a very small power, therefore I expect that in about a week, dependent on the amount of sunshine, the battery will fill.
• Note: Since a LED is always on, the board is bleeding some power, I'll investigate if this is more than the solar panels generate. If so, I'll add a step to desolder the LED, and prevent the power bleed.