Magnetic Induction In terms of Creating Charge

[marias3]

Hi,
I'm an industrial designer and I was wondering if there is a way to charge a battery through magnetic induction. I have heard that the way some stop lights work is there are coils below the road, and when the steel body of a car goes over it, it creates a change in charge in those coils. Is there a way a similar idea could be used to charge small batteries?
thanks

 

[vadar]

I would think that it is possible however it is not practical.

The traffic lights are using the induction as a sensor, and rely on the moving car, and not as a power source.

If you wanted to charge a battery by the same principal, say in a lab, you would have to physically move something to create that induction, for example youself, or maybe a motor moving a magnetic core through the solenoid, which in turn uses power from another source.

So why not just use the power to charge the battery straight from the main source of power?

Hope that helps

 

[marias3]

I was hoping to rig up some sort of device that could power the pedestrian/street lights via the traffic that goes over them. Also I was hoping this would be a cheaper solution than using solar power in areas where there might not already be power lines. is this feasible?

 

[vadar]

If you do some quick calculations with Faradays law you will start to see the problem. A very small voltage would be created across a winding under the road, due to a number of things; The car being realitivlty far from the coil, the coil is underground, cars may not come past so energy would need to be stored. So you would not get enough power out of one coil.

If a lightbulb is ~75W or so, you are not going to create enough energy to run these lightbulbs all night. At a guess you would need probably 20-30 large coils, under a busy road were the cars are going >80km, to start to even get the energy you need. Just a guess though I didn't do the calculations :-)
Who knows, maybe a smart idea will get around this problem...