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Wireless Charging with Supercapacitors

  • Writer: Mary Margret
    Mary Margret
  • Mar 22
  • 4 min read

The Future of Fast, Convenient Energy Transfer

Wireless charging and supercapacitors are two innovative technologies that, when paired, could transform how we power devices and vehicles. This blog explores their synergy, using concrete numbers and real-world examples to highlight their potential. While avoiding complex equations, we’ll use statistics—like electric buses charging in seconds or wearables ditching plugs—to make the possibilities clear and compelling.


1. What IS Wireless Charging and Supercapacitors?

Let’s cover the basics:

  • Wireless Charging: This technology transfers energy without cables, using electromagnetic fields. A familiar example is a phone charging pad, where a coil in the pad generates a magnetic field, and a coil in the device captures it, converting it back into electricity. Efficiency typically ranges from 70% to 90%, depending on coil alignment and distance.

  • Supercapacitors: Unlike batteries, which store energy via chemical reactions, supercapacitors store it electrostatically, allowing rapid charging and discharging. They deliver an impressive power density of up to 10,000 watts per kilogram (W/kg), compared to batteries’ 1,000-3,000 W/kg. However, their energy density is lower, at 5-10 watt-hours per kilogram (Wh/kg), versus 150-250 Wh/kg for batteries.

Together, wireless charging and supercapacitors enable fast energy transfer, wire-free convenience, and immediate power availability—ideal for applications needing quick, high-power bursts.

2. How Wireless Charging Works with Supercapacitors

Here’s the process in action:

  • A transmitter coil in the charging pad creates an alternating magnetic field, typically at 20 kHz to 150 kHz for optimal efficiency.

  • A receiver coil in the device captures this field and converts it into electricity via a rectifier circuit.

  • The supercapacitor stores the energy, leveraging its ability to handle large currents and charge in seconds or minutes.

Setting Up Supercapacitors in Series for Higher Voltages

Supercapacitors can be connected in series to boost voltage:

  • Each unit has a voltage limit, usually around 2.7V. In series, voltages add up—two provide 5.4V, ten offer 27V, and so on.

  • This adaptability suits everything from low-voltage wearables to high-voltage tools.

  • However, stacking them in series reduces total capacitance, which can limit energy storage capacity. This trade-off requires careful management to balance voltage and energy needs.

For example, ten 100F supercapacitors (each 2.7V) in series yield 27V with a total capacitance of 10F (since 1/C_total = 1/C₁ + 1/C₂ + …). This stores 3,645 joules (J) or about 1 Wh (Energy = ½ × C × V²), delivering high voltage for quick, powerful bursts.



3. Advantages of Wireless Charging with Supercapacitors

This combination brings several notable benefits:

  • Rapid Charging: Supercapacitors charge in seconds or minutes, far faster than batteries, enhanced by wireless delivery.

  • Durability: No cables or plugs mean less wear on connectors.

  • High Power Output: With 10,000 W/kg, supercapacitors excel in applications needing sudden energy surges, like EV acceleration or tool operation.

  • User Convenience: Wireless charging is simple and intuitive for all users.

  • Efficient Energy Use: Despite 10-30% efficiency losses, the speed of supercapacitors minimizes waste compared to slow battery charging.

  • Voltage Flexibility: Series setups allow customization without extra hardware.


4. Real-World Applications: Where Speed and Convenience Shine

Here are some practical examples, with numbers showing how series configurations enhance performance.


Electric Buses: Charging in Seconds

Shanghai’s electric buses recharge at stops in seconds:

  • Energy Storage: A 1 kWh (3,600,000 J) supercapacitor bank powers a few kilometers, using series-parallel setups for voltage and capacity.

  • Charging Time: 30 seconds during boarding.

  • Power Required: Delivering 1 kWh in 30 seconds requires 120 kW (1 kWh * 3600 s/h / 30 s). At 85% efficiency, the source supplies ~141 kW.

  • Series Setup: For 600V, 222 supercapacitors (2.7V each) in series provide 600V. With 3,000F units, total capacitance is 13.5F, storing 2,430,000 J (0.675 kWh)—near the target with parallel banks.


Wearable Devices: Power Without Plugs

Supercapacitors suit devices like fitness trackers:

  • Energy Storage: A 1F supercapacitor at 2.7V stores 3.645 J (0.001 Wh). For 3.3V, two in series (5.4V) work with a regulator.

  • Charging Time: A 5W charger at 80% efficiency (4W) charges it in 0.91 seconds (3.645 J / 4 J/s).

  • Benefit: A quick tap on a pad provides instant power, skipping tiny connectors.


Industrial Tools: Reducing Downtime

Cordless tools like drills stay active:

  • Energy Storage: Four 100F supercapacitors in series (2.7V each) give 10.8V and 25F, storing 1,458 J (0.4 Wh).

  • Charging Time: A 20W charger at 85% efficiency (17W) recharges in 85.8 seconds (1,458 J / 17 J/s).

  • Advantage: Quick wireless recharges between tasks, with series voltage driving motors.


Micro-Drones: Rapid Turnaround

Micro-drones for urgent missions recharge fast:

  • Energy Storage: Five 50F supercapacitors in series (2.7V each) provide 13.5V and 10F, storing 911.25 J (0.25 Wh).

  • Charging Time: A 50W charger at 90% efficiency (45W) recharges in 20.25 seconds (911.25 J / 45 J/s).

  • Use Case: Ideal for short-range, time-sensitive tasks, with series voltage powering systems.

5. Challenges and Future Directions

Challenges remain:

  • Efficiency Losses: Efficiency (70-90%) drops with misalignment or distance. For instance, a few centimeters of misalignment might reduce efficiency to 60%, doubling charging time—critical for EVs requiring precision.

  • Limited Energy Storage: With 5-10 Wh/kg versus batteries’ 150-250 Wh/kg, supercapacitors suit short bursts, not long-term storage (e.g., extended EV range or wearable runtime).

  • Balancing in Series: Series setups need voltage balancing to avoid overcharging, often requiring extra circuitry.

Future advancements include:

  • Improved Coil Designs: Multi-coil systems and alignment tech are hitting 95% efficiency.

  • Higher Power Systems: 200 kW wireless systems could slash charging times further.

  • Hybrid Systems: Pairing supercapacitors and batteries, with series optimization, could blend high energy and power.

6. A Powerful Partnership

Wireless charging with supercapacitors—especially in series—offers fast, convenient, high-power energy transfer. From buses charging in seconds to plug-free wearables, applications shine with 70-90% efficiency and rapid charge times. As efficiency and power improve, this technology will grow even more vital.

Key Takeaways:

  • Supercapacitors enable ultra-fast charging, enhanced by wireless tech.

  • Series setups scale voltage flexibly across applications.

  • Real-world uses, like buses and drones, prove its practicality.

  • Challenges like energy density persist, but research is advancing.

This is the future of energy—fast, wireless, and ready.

 
 
 

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