IT Technology: Inductive Charging / Wireless Charging / Cordless Charging

Inductive charging (Wireless charging or Cordless charging) uses an electromagnetic field to transfer energy between two objects. This is usually done with a charging station. Energy is sent through an inductive coupling to an electrical device, which can then use that energy to charge batteries or run the device.

Induction chargers typically use an induction coil to create an alternating electromagnetic field from within a charging base station, and a second induction coil in the portable device takes power from the electromagnetic field and converts it back into electrical current to charge the battery. The two induction coils in proximity combine to form an electrical transformer.

Greater distances between sender and receiver coils can be achieved when the inductive charging system uses resonant inductive coupling.

Here are the pros and cons of the inductive charging:

Pros

• Lower risk of electrical shock or shorting out when wet because there are no exposed conductors, for example toothbrushes and shavers, or outdoors
• Protected connections - no corrosion when the electronics are all enclosed, away from water or oxygen in the atmosphere
• Safer for medical implants - for embedded medical devices, allows recharging/powering through the skin rather than having wires penetrate the skin, which would increase the risk of infection
• Convenience - rather than having to connect a power cable, the device can be placed on or close to a charge plate or stand
• Easier than plugging into a power cable (important for disabled people)

Cons

• Lower efficiency, waste heat - The main disadvantages of inductive charging are its lower efficiency and increased resistive heating in comparison to direct contact. Implementations using lower frequencies or older drive technologies charge more slowly and generate heat within most portable electronics
• More costly - Inductive charging also requires drive electronics and coils in both device and charger, increasing the complexity and cost of manufacturing
• Slower charging - due to the lower efficiency, devices can take longer to charge when supplied power is equal
• Inconvenience - When a mobile device is connected to a cable, it can be freely moved around and operated while charging. In some implementations of inductive charging (such as the Qi standard), the mobile device must be left on a pad, and thus can't be moved around or easily operated while charging. In practice, this defeats the point of wireless charging as the convenience factor is removed
• Incompatibility - Unlike (for example) a standardized MicroUSB charging connector, there are no de facto standards, potentially leaving a consumer, organization or manufacturer with redundant equipment when a standard emerges. (Note: Qi has become a standard adopted by many companies such as Google and Nokia.)

For your information, newer approaches reduce transfer losses through the use of ultra-thin coils, higher frequencies, and optimized drive electronics. These results in more efficient and compact chargers and receivers, facilitating their integration into mobile devices or batteries with minimal changes required. These technologies provide charging times comparable to wired approaches, and they are rapidly finding their way into mobile devices. For example, the Magne Charge vehicle recharger system employs high-frequency induction to deliver high power at an efficiency of 86% (6.6 kW power delivery from a 7.68 kW power draw).

References:

1.  Wireless Charging

http://mobilewirelesscharging.blogspot.com/

2.  2013 Best Wireless Charger Comparisons and Reviews

http://wireless-charger-review.toptenreviews.com/

3.  Energizer Inductive Charger Review

http://www.youtube.com/watch?v=8ZaDXaUWzfo