Description

Greetings, everyone. Meet SolMate; just clip it to your bag, flip the panel toward the sun, and it charges your devices while you’re on the move. Clip it, flip it, charge it—it’s that easy.
I started mountain trekking recently and needed a solar-powered battery bank to keep my phone charged. I looked around online, but most options were either too expensive or didn’t look great. So I figured I’d make one myself—and add a bit of industrial design to make it feel more like a proper product.

Details

The 2W high-efficiency PTFE panel we're using can supply 5V 400mA, which is more than enough to charge our 2000mAh Li-ion battery.

Solmate's ultra-slim body and a custom carabiner hook make it the perfect companion for outdoor enthusiasts, travelers, and backpackers—simply clip it to your bag and let it charge while you explore. Whether you're hiking through the hills or commuting through the city, SolMate keeps your devices energized using nothing but sunlight.

DESIGN PROCESS

SolMate’s body was designed in Fusion 360, drawing inspiration from the Lenovo Yoga Tablet’s distinctive form. Just like the Yoga’s cylindrical edge that allows users to prop the tablet at an angle, SolMate features a similar contour—not just for aesthetics, but to enhance usability and portability.

This thoughtful shape makes it easy to grip, clip, and carry, while maintaining a slim profile that blends seamlessly with your gear. Not even aesthetics; a solar panel needs to be placed at an angle facing towards sunlight. This shape makes sure it is always placed at an angle, which will allow the user to get the max potential of the solar panel!

SolMate is built from two main parts: the main body, which holds the solar panel, battery, and circuit, and the lid, which pressure-fits from the top to seal everything in place.

One small but useful design touch was adding a custom carabiner clip. Originally made for climbing gear, carabiners are spring-loaded loops that make it easy to attach things securely. These days, they’re everywhere—used to clip water bottles, keys, or gadgets to backpacks.

For SolMate, it means you can just hook it on and let it charge while you move. Simple, secure, and built for the outdoors.

Unlike traditional metal carabiners with spring-loaded gates, our custom carabiner is made from regular PLA and operates on a simple yet effective principle: material bend. The clip is designed with a narrow opening and a slightly curved shape that allows the plastic to flex when pressure is applied.

PCB DESIGN

Here we are using the IP5306 Power Management IC Setup, which we have previously used in many of our battery-related projects. This SOIC8 package IC can provide a stable 5V 2.4A from a 3.7V lithium-ion or LIPO cell and also includes many important functions such as overcharging protection, overdischarge, battery fuel level, and charging status.

Below is its datasheet if you want more info on this IC.

https://www.skytech.ir/DownLoad/File/2566_IP5306.pdf

We created the board outline in PCB CAD by following the customized circuit design from our Fusion 360 CAD file. We finalized the board layout by placing all the components in order with the CAD's measurements. Once everything lined up, we prepared the final board for fabrication.

NextPCB PCB Service

After completing the PCB design, Gerber data was sent to HQ NextPCB, and an order was placed for a white solder mask with black silkscreen.

After placing the order, the PCBs were received within a week, and the PCB quality was pretty great.

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Files

SOLAR BOOK v5.f3d

fusion - 2.88 MB - 09/13/2025 at 20:38

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SOLAR BOOK v5.step

step - 1.13 MB - 09/13/2025 at 20:38

Download

SCH.pdf

Adobe Portable Document Format - 149.73 kB - 09/13/2025 at 20:38

Preview

CARABINER.3mf

3mf - 185.07 kB - 09/13/2025 at 20:38

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holder.3mf

3mf - 166.23 kB - 09/13/2025 at 20:38

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Build Instructions

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PCB ASSEMBLY PROCESS

PCB assembly starts by applying solder paste to each SMD pad using a dispensing syringe. We’re using standard 63/37 Sn-Pb solder paste. Once that’s done, each SMD component is placed in position using ESD-safe tweezers.
The board then goes onto a mini reflow hotplate, which heats it from below. As soon as the temperature hits around 200°C, the solder paste melts and the components are soldered in place.
Next, we move on to the through-hole components—starting with the USB port, then the push button, and finally the Type-C port. After placing them, we flip the PCB and solder the through-hole pads using a soldering iron. That wraps up the full assembly process.

POWER SOURCE

For power, we’re using a 3.7V 2000mAh Li-ion cell, which works well for this setup. Since the panel is rated at 2W, going with a larger battery would just slow down charging.
We connect the battery’s positive lead to the positive terminal on the circuit and the negative to the negative terminal.
Pressing the push button powers up the circuit, and the indicator LED confirms it’s working.
To be sure everything’s running properly, we plug in a USB power meter and get a stable 5V output, which means the setup is good to go.

2W PTFE SOLAR PANEL

The 2W PTFE solar panel is the project's main highlight. Polytetrafluoroethylene, or PTFE, is the same substance used to make Teflon and other non-stick cookware, so this isn't your typical solar panel.

In place of conventional glass, PTFE is used in solar panels as a flexible, lightweight, and weather-resistant layer. This means that the panels we use are lighter, thinner, and have a non-breakable layer, which is significantly better compared to traditional glass.

It's lighter but has a drawback, which is efficency, its effiecny is slightly lower than traditional glass panels because of the fact that the PTFE layer tends to scatter incoming sunlight more, which means less direct light hits the solar cells underneath. That scattered light either gets reflected away or diffused inefficiently, leading to lower energy conversion compared to glass-covered panels that use anti-reflective coatings and high-transmission surfaces.

For our testing, we connected two wires to the Positive and negative terminals of the panel, then used a multimeter to measure the voltage which was around 3.9V. It's lower because we are in a room; this panel voltage can reach to 6V at no voltage but its nominal voltage is around 5V making it ideal for charging the Lithium Cell via Power management circuit.

Discussions

SolMate

Description

Details

DESIGN PROCESS

PCB DESIGN

NextPCB PCB Service

HQDFM: Free Online Gerber Viewer and DFM Analysis Tool