Electric Vehicle - Inductive Charging, what about it?

One popular technology that has popped up in many discussions around charging your electric vehicle, is inductive charging. There are some myths surrounding this technology, people are not familiar enough with it. Or so they think...  

Inductive power transfer is not all that new, probably you have an electric toothbrush which uses the very same principle to charge up. It is not unlikely you have an electric kettle to boil water, with such a connection. Applying this concept is rather new, but then again, so are the electric vehicles that have such a good use for this technology.



An inductive charger as it would fit under a vehicle - Link


Inductive charging an electric vehicle can be applied to parked cars, where the vehicle charges up while standing idle for some time. More appealing to the mind's eye is inductive charging while driving in your electric vehicle. Imagine getting power from the road, there'd be no need to stop any more to fill up your car! Of the companies involved with inductive charging while driving, Hotroad is one of them.


The magic

So how does the magic work? From early on we are familiar with electric power being able to go to one place to another, as long as there is a physical connection available. Be it a copper wire, or some other conducting medium.


The basis for inductive power transfer are two coils, one which is referred to as the transmitter, the other is the receiver. The transmitter is located on the floor, or incorporated in the road. When you allow a current to pass through the coil, it induces a magnetic field. The magnetic field is picked up by the second coil, which results in a current in the vehicle, either to store or use directly.


Magnetic field shown around a magnet, the pattern at the end is what comes 'out' of the coil - Link


The physics behind it is best described here in this Wikipedia article. The efficiency of the system has a lot to do with how much of the magnetic field that is created in the transmitting coil, is received by the receiving coil.

In short: the larger the distance between the two coils, the less efficient the power transfer is. Effectively, at larger distances, more of the transmitted magnetic field is missed by the receiving coil. The more of the transmitted magnetic field is ‘caught’ by the receiver, the better.


From a safety point of view, there is just a magnetic field between the coils, there is no physical power being transferred; no open contacts with voltages or currents to get hurt. It is also why this technology is used in the electric toothbrush; you can transfer power without water getting in the way or creating a dangerous situation. From a presentation given by Conductix Wampfler I attended once, I understood that the magnetic field that can be measured inside a vehicle as a result of the inductive charging, is less than the field that surrounds your mobile phone.



Ultimately inductive charging will mean a new standard in electric vehicle charging, but also one which is easily upgradeable. Since the basics will always remain the same, a set of coils, future versions of the system will always remain compatible with existing infrastructure. It is a technology that is applicable in static parking situations, but also in dynamic driving situations. Even though many will point out that inductive transfer will come at a cost of decreased efficiency, the benefits will far outweigh this. Even this early in the development of the technology an efficiency of 90% can be achieved, which is only going to improve over time.


The convenience factor will win, it will allow drivers to park their car and not bother with plugging in, but more importantly it will allow them to drive and get a charge to top up their batteries. The time of Plug & Play is over, it is time to Unplug & Drive. Similar how mass produced cars brought freedom to go where you wanted, when you wanted, Hotroads will bring people the freedom to choose when you want to stop, instead of letting the limitations of your car determine when you stop.