Wireless Battery Charging

Wireless Battery Charging is a battery recharge using an electromagnetic field to transfer energy between two objects through electromagnetic induction. This wireless charging technology was originally used to recharge batteries for relatively small mobile devices such as Smartphones and Smartphones. But today it has evolved into a technology that can recharge larger devices such as Car Batteries and other large devices.

This wireless charging or wireless charging usually uses an inductive clutch between two circuits to transfer power from one circuit to another and has no physical electrical contact so it is more convenient and also does not depend on connector contacts that can wear out after many charging cycles.

Wireless Battery Charging is usually flat or flat to facilitate the placement of devices to be recharged. In its application, wireless charging consists of two flat inductor reels whose primary side is connected to the power source while the secondary side is near the devices to be charged.

Some aspects of which affect how wireless battery charging works is the efficiency, diameter of the coil or coil and frequency used. The next aspect to note in the design of wireless charging is filtering and ensuring that wireless power transfer does not interfere with other electronic circuits, especially on power-receiving devices.

Wireless Charging Standard

There are several wireless charging standards that have been developed and can be found on the market. Among these standards are two of the most common standards found, namely Qi Wireless Charging Standard and A4WP Wireless Charging Standard.

1. Qi Wireless Charging Standard

The Qi Wireless Charging Standard was the first to be invented and has a fairly dominant market share. This standard has been adopted by the majority of phone manufacturers to recharge their phone batteries. Basically this Qi Wireless Charging Standard is an inductive system that uses relatively low frequencies (between 110 and 205 kHz for low power and 80 to 300 kHz for medium power) for power transfer.

2. A4WP Standard

The A4WP wireless power standard was developed slightly slower than the Qi standard. This A4WP standard uses resonance techniques along with a higher power transfer frequency of 6.78 MHz for power, and 2.4GHz for control signals. This A4WP standard also allows simultaneous charging for multiple devices.

Advantages and Disadvantages of Wireless Battery Charging

The following are some of the advantages and disadvantages of Wireless Battery Charging.

Advantages of Wireless Battery Charging:

  • Convenience and Practical – Just put a device that requires charging to the charging area.
  • Reduce wear on plugs and sockets – as there is no physical connection, no problems with connector wear and more. Physically the system is more powerful than the one that uses the connector.
  • Impurities resistance – some applications operate in highly contaminated environments. Since there are no connectors, the system is much more resistant to contamination.
  • More suitable for applications in medical environments – using wireless charging is not required connectors that can hold bacteria and others so it is safer to use on medical equipment that requires battery power.

Disadvantages of Wireless Battery Charging :

  • Additional complexity – this system requires a more complex system to transfer power through a cordless interface.
  • Additional costs – because these systems are more complicated than traditional wired systems, wireless chargers will be more expensive.
  • Reduced efficiency – there are disadvantages to the wireless battery charging system such as resistivity losses on coils and others. But basically it can still be about 85 – 90% efficiency when compared to charging with cables.

Capacitive Wireless Charging

Wireless charging or wireless charging of CWCS-type electric cars is done using displacement current due to the variation of electric fields. Instead of magnets or reels as transmitters and receivers, clutch capacitors are used here as wireless power transmissions. AC voltage was first supplied to the power factor correction circuit aimed at improving efficiency, maintaining voltage levels and reducing transmission losses. It is then supplied to the H-bridge for high frequency AC voltage generation. This high-frequency air conditioner applied to the transmission plate causes the development of an oscillating electric field and then causes the displacement current on the receiver plate through static electro induction.

The receiver-side AC voltage is converted to DC and then charged via BMS by a series of rectifiers and filters. The frequency, voltage, size of the clutch capacitor and the air gap between the transmitter and the receiver affect the amount of energy transfer. The operating frequency is between 100 to 600 KHz.

Wireless Charging Permanent Magnet Gear (PMWC)

In this wireless charging technology for electric cars, each transmitter also receiver consists of haunted twists and permanent magnets synchronized in the twist. The principle of transmitter side operation is similar to motor operation. When we apply the AC current to the transmitter, it will cause the mechanical torque on the transmitter magnet to cause its spin. Due to changes in transmitter magnetic interaction, the PM field causes torque on the PM receiver resulting in rotation in sync with the transmitter magnet. Now the change in the receiver’s permanent magnetic field causes the production of ac current in the twist that is, the receiver acts as a generator as a mechanical power input to the receiver PM which is converted into electrical output on the receiver’s twist. A rotating permanent magnetic clutch is called a magnetic gear. The resulting AC power on the receiving side is fed to the battery after repair and filtered through the power converter.

Inductive Wireless Charging (IWC)

The basic principle of wireless charging or wireless charging of electric cars is faraday induction law. Here, wireless transmission is achieved by inducing the magnetic field between the transmitter coil and the receiver. When the main AC supply is applied to the transmitter coil, it creates an AC magnetic field that passes through the transmitter coil and this magnetic field moves electrons in the receiver twist causing the AC power output. This air conditioning output is repaired and filtered and then fills the car’s energy storage system. The number of transfers on the electric car wireless charger depends on the frequency, joint inductance and distance between the transmitter and the receiver coil. The operating frequency of IWC electric car wireless charging is between 19 to 50 KHz.

Wireless Charging Inductive Resonant (RIWC)

Wireless charging of this electric car is basically a resonator with a high quality factor transmitting energy at a much higher level. Because it operates on resonance, even with a weaker magnetic field, we can transmit an amount of energy as large as the transfer capacity as in IWC. Power can be transferred remotely without wires. Maximum power transfer through the air occurs when the transmitter and receiver twists are arranged in such a way that the frequency of the two resonance coils must match. So in order to obtain a good resonance frequency, additional network compensation of parallel-series combinations is added to the transmitter coil as well as receiver. Additional compensation networks on this listrk car wireless charger should adjust the increased resonance frequency as well as reduce additional losses. Riwc operating frequency is between 10 to 150 KHz.

All the wireless charger technology of electric cars or wireless charging for wevcs electric cars above will certainly increase the interest of consumers to have this type of car, because it gives more choices.


For consultation on the above topic, please contact PT. Omazaki Envirokal Prakarsa, including EVCS installation plan for household, office, commercial, industrial, or public charging stations (SPLU). Training of wireless charging technology for electric cars (WEVCS) or wireless electric car chargers can be seen on the Omazaki Training page.