Research. Electronics¶
Research: Flexible Solar Panels for Wearable Applications¶
1. Scope and goal¶
This research explores the realistic use of small flexible (thin-film) solar panels in clothing and wearable objects, focusing on:
- feasibility of charging consumer electronics (e.g. a smartphone),
- correct electrical architecture,
- comparison between direct battery-based systems and power-bank-based systems.
The emphasis is on DIY-accessible components rather than experimental lab-only solar textiles.
2. Energy requirements (baseline)¶
A typical modern smartphone:
- Battery capacity: 4000–4500 mAh
- Nominal battery voltage: ~3.7 V
Energy stored:
≈ 15 Wh
Considering real losses (conversion, instability, shadows, movement):
≈ 18–20 Wh required for one full charge
3. What small flexible solar films realistically provide¶
Typical DIY flexible mini-panels:
- Nominal power: 0.3–1.5 W
- Technology: amorphous thin-film or flexible mono-crystalline
- Real power in wearable conditions: 30–60% of nominal
Assuming good outdoor conditions:
Resulting panel count¶
- 1 W panels → 6–8 panels for one full phone charge
- 0.3 W panels → 13–15 panels (mostly impractical; suitable for demos or sensors)
4. Why a phone cannot be charged directly from solar panels¶
Solar panels:
- do not output stable voltage or current,
- react instantly to shadows, folds, and body movement.
Smartphones:
- require stable 5 V USB input,
- disconnect or refuse charging when voltage fluctuates.
Direct connection (panel → phone) is not viable.
5. Role of each system component¶
5.1 Battery (energy buffer)
¶
The battery:
- smooths unstable solar input,
- stores energy collected slowly,
- delivers energy quickly when needed.
Without a battery:
- charging constantly drops and reconnects,
- system becomes unusable.
5.2 Solar charge controller
¶
A dedicated solar-aware charge controller is mandatory.
Functions:
- accepts unstable solar input,
- safely charges Li-ion / Li-Po cells,
- prevents over-charge and brown-outs.
⚠️ Standard USB chargers (e.g. TP4056 alone) are not suitable for solar panels.
5.3 Boost (step-up) converter
¶
Li-ion batteries operate at:
3.0–4.2 V
USB devices require:
The boost converter:
- raises battery voltage to USB-compatible 5 V,
- stabilizes output under variable load.
6. Complete functional architecture (battery-based)¶
[Flexible solar panels]
↓
[Solar charge controller]
↓
[Flat Li-Po battery (3.7 V)]
↓
[5 V boost converter]
↓
[Phone / device]
Each block is mandatory for reliability and safety.
7. Using a power bank instead of a bare battery¶
7.1 What a power bank already includes¶
A power bank integrates:
- Li-ion battery,
- charge controller,
- boost converter,
- protection circuitry.
It is essentially battery + boost + safety in one enclosure.
7.2 Why solar panels cannot feed most power banks directly¶
Most consumer power banks:
- expect stable USB input,
- shut down at low current,
- reset under fluctuating voltage.
Direct solar → power bank connection usually fails.
7.3 Correct power-bank-based architecture¶
[Flexible solar panels]
↓
[Solar charge controller]
↓
[Power bank (USB input)]
↓
[Phone / device]
The solar controller “pretends” to be a stable USB charger, which the power bank can accept.
8. Choosing a suitable power bank¶
Recommended characteristics¶
- Simple 5 V USB input
- No fast-charge (QC / PD) dependency
- Can charge at low currents (≈100–300 mA)
- Capacity: 2000–5000 mAh (larger is unnecessary for wearables)
Best option¶
- DIY power bank modules (known controller chips, predictable behavior)
- Easier to integrate into garments or accessories
9. Battery vs power bank — comparison¶
| Criterion | Bare battery system | Power bank system |
|---|---|---|
| Circuit complexity | Higher | Lower |
| Reliability | Depends on design | High |
| Thickness | Minimal | Higher |
| Shape flexibility | Very high | Limited |
| USB output | External | Built-in |
| Wearable integration | Advanced | Easier |
| Best use case | Research, textile experiments | Practical wearable charging |
10. Practical conclusions¶
- Charging a phone fully from wearable solar panels is possible but slow
- Expect:
- +30–70% phone charge per sunny day
- emergency or maintenance charging, not instant power
- Solar wearables work best when:
- energy is stored first,
- then released in a controlled way.
Recommended default approach¶
Flexible solar panels → solar charge controller → power bank → phone
This is the most stable, safe, and reproducible configuration for wearable solar systems today.
11. Research positioning¶
From a research and design perspective: - Solar wearables are energy-harvesting systems, not power supplies. - Their value lies in: - autonomy, - resilience, - hybrid use with stored energy, - expressive and functional integration into textiles.
They are most successful when treated as slow, ambient energy collectors, not replacements for wall chargers.
BoM bill of materials¶
Bill of Materials (Wearable Solar Jacket – 8 Panels)¶
| # | Component | Description / Suggested SKU | Qty | Unit Price (approx) | Total Price | Notes |
|---|---|---|---|---|---|---|
| 1 | Flexible Solar Panel 1.5 W 5 V | Flexible mini solar panel with USB output / DIY leads | 8 | $9.50 – $14.00 | $76 – $112 | ~1.5 W each, flexible PET lamination for wearable use |
| 2 | Solar Charge Controller (CN3065 mini module) | Mini Li-ion/LiPo solar charging board (4.4–6 V input, up to ~500 mA) | 1 | $2.15 – $3.50 | $2.15 – $3.50 | Module charges single-cell battery from solar input |
| 3 | USB Power Bank 5000 mAh | Standard USB power bank with 5 V output | 1 | ~$10 – $20 | ~$10 – $20 | Must support low-current charging on USB input |
| 4 | Wiring – flexible stranded wire | AWG 26–30 silicone wire for panel interconnects | ~3 m | ~$2 | ~$2 | Enough to interconnect panels and controller |
| 5 | Connectors (optional) | JST-PH / 2-pin connectors for detachable panels | Set | ~$3 | ~$3 | Optional for modular panel connections |
| 6 | Textile mounting materials | TPU/PET clear pockets, sewing thread/adhesive | — | ~$6 | ~$6 | Protect panels and stitches when worn |
| 7 | Mechanical protection | Heat-shrink / strain relief | — | ~$2 | ~$2 | Protect cable exits, reinforcement |
Total Estimated Cost (without transportation to Armenia)¶
| Budget tier | Estimated total |
|---|---|
| Low end | ~$102 |
| High end | ~$148 |
Materials¶
Assembly Notes¶
-
Solar Panels: Mount 8 flexible panels on outer jacket surface (front + back or shoulders) in a series/parallel layout that yields ~5 V nominal. Because many DIY panels already have USB leads / wiring, you can parallel groups to boost current.
-
Charge Controller: Use the CN3065 solar charging module to manage solar input — it accepts 4.4–6 V from the array and regulates charge for a battery or storage device.
-
Power Bank: Connect the output of the solar controller to the USB input of the power bank. Choose a bank that accepts charging at lower currents (~100–300 mA) so it will accept solar charge.
-
Wiring: Use flexible silicone wire and strain relief to handle movement; optional connectors allow panels to be detached for washing.
-
Protection & Mounting: Panels should be protected with clear TPU windows and sewn pockets; wiring needs strain relief to withstand flexing due to motion.
Example Component Details (Reference)¶
Flexible Solar Panel ~1.5 W 5 V (DIY)¶
- Approx. $9.50–$14 each on secondary marketplaces (e.g., eBay) :
CN3065 Mini Solar Charger Module¶
- Typically ~$2.15 on electronics parts stores for DIY modules based on CN3065 chip
USB Power Bank (5000 mAh)¶
- Consumer-grade USB battery pack (no fast-charging necessary).
Price Assumptions & Variability¶
- Panel prices fluctuate based on seller and shipping; buying in bulk (8+) usually reduces unit cost.
- Power bank choice affects total significantly but 5000 mAh range balances weight and capacity.
- Optional connectors and textile integration materials vary widely by regional availability.
References¶
-
Flexible 1.5 W monocrystalline flexible mini panels (~5 V USB) found widely on marketplaces (~$9–14 each)
-
CN3065-based mini solar charger modules — simple solar-optimized Li-ion chargers (~$2–3)
Solar Panels Ordered for the Project¶
I ordered two types of flexible solar panels from AliExpress for our wearable solar power project:
Ordered Panel Types¶
- Flexible Thin Film DIY Solar Panel (0.5 W / 1.5 V)
ℹ️ This is a small, lightweight thin-film panel optimized for DIY, educational or low-power experiments.
These panels are small flexible modules intended for hobby solar projects. They generate low power at low voltage, so they are ideal for combining into a larger array rather than using independently.
- Flexible Thin Film DIY Solar Panel (s0.3W 1.5V )
This panel is of a similar size and specification to the first, also producing a low nominal voltage and power output suitable for modular assembly.
How These Panels Can Be Used Together¶
1. Electrical Characteristics¶
Each panel has approximately:
- Nominal power: ~0.5 W
- Nominal voltage: ~1.5 V
Because each panel produces low voltage and low current, using one alone is insufficient for charging a power bank or device. They must be electrically combined to produce usable voltage and current.
2. Combining Panels into an Array¶
To use these panels together in a single wearable solar array, we connect them in series and parallel combinations:
Series for Voltage¶
Connecting panels in series adds their voltages. For example:
Panel A (1.5 V)
Panel B (1.5 V)
Panel C (1.5 V)
Panel D (1.5 V)
≈ 6 V total
This gives a higher, usable voltage level required by most solar charge controllers.
Parallel to Increase Current¶
Once you have several series strings at the same voltage, you can connect those strings in parallel to increase current:
String 1: 4 panels in series → ~6 V String 2: 4 panels in series → ~6 V
Parallel combined → ~6 V @ higher current
This series-parallel arrangement increases both voltage and current in a controlled way.
3. Why Series-Parallel Arrangements Matter¶
- Series increases voltage: Panels that each output only ~1.5 V need to be combined to reach a voltage that can be used by a solar charge controller or regulator.
- Parallel increases current: Once at an acceptable voltage, adding parallel strings increases the total current without increasing voltage, allowing more power to be collected from multiple panels.
When combining panels of the same type, this approach maximizes total harvested power while keeping the electrical output in a usable range.
4. Mismatch and Panel Uniformity¶
Because both ordered panel types have similar specifications (≈1.5 V nominal), they can be mixed in the same series and parallel groups. However: - It is critical to keep series strings at the same number of panels to avoid current mismatch. - For example, a series string should not mix 0.5 W and 0.3 W panels without considering current limits, because the series current will be limited by the lowest-current panel in that string.
5. Integration with Charge Controller and Power Bank¶
Once the panels are combined into a series-parallel array at a usable voltage (≈5–6 V or higher): 1. The array connects to a solar charge controller that manages power from the panels. 2. The charge controller feeds a Li-ion / Li-Po battery or directly charges a power bank with appropriate input. 3. The power bank then provides stable output to charge phones or other devices.
This staged approach ensures that the low-voltage panels are used effectively and safely, and that the energy harvested during sunlight hours is stored and regulated before powering devices.
Summary¶
- I ordered two flexible, thin-film solar panels (≈0.5 W / 1.5 V) for my wearable project.
- These panels are suitable for modular combination (series + parallel) because of their similar electrical characteristics.
- By arranging them into series and parallel groups, we can achieve a higher voltage and higher current output, which can then be regulated via a controller and stored in a battery or power bank.
This configuration allows a set of small panels to work together effectively in a wearable solar charging system.