How do these new non plug in battery chargers work?

[bdewoody]

I'm seeing more and more of these advertised but they don't state whether a special battery is required. How does just setting a device ie. cell phone on top of it charge the devices battery?

 

[adrenalynn]

It requires an antenna in the base and an antenna attached to the battery. The devices are then coupled inductively.

 

[bdewoody]

I understand how an electrical circuit works, sort of, but I can't grasp how a battery can be charged without a physical connection to the charging source. I've seen stuff about Tesla's idea of transmitting electricity via giant versions of one of his coils and devices being able to take in that energy and function but I don't understand how it is supposed to work. It seems if it does that is a way vehicles could get their energy, but the trick there being how to meter it and have the customer pay for his/her share of the usage.

 

[adrenalynn]

That could be done via RFID.

As far as how it's coupled - it's inductive RF. The same way a radio works.

I've built a handful of inductive chargers. It's really pretty simple in concept and has been around forever. Shavers and toothbrushes have been doing it for at least a couple decades.

The problem you'll have with vehicles is that they need a _lot_ of current to make even a dent in their battery charge. And inductive coupling just doesn't deliver that.

 

[Mee_n_Mac]

I understand how an electrical circuit works, sort of, but I can't grasp how a battery can be charged without a physical connection to the charging source.

Ever thought about how a transformer works ?
http://en.wikipedia.org/wiki/Inductive_charging

And apparently these pads had been around longer than I thought ...
http://www.gizmag.com/go/8191/

October 18, 2007 The idea of wireless charging is an attractive one - do away with messy cords and chargers in favor of a wire free charging pad that does the job for multiple devices by simply placing it on the pad's surface. The concept has been around for several years, but commercialization has been slow. Now WildCharge is offering a wireless charging system for Motorola RAZR phones with an adapter for iPod Nano just around the corner.


http://www.newscientist.com/article/dn6 ... dgets.html

One charging pad could power up all gadgets
10:09 21 January 2005 by Barry Fox

Finding the right battery charger for your cellphone, digital camera, camcorder or PDA among the sea of anonymous black boxes that clutter our homes is a complete pain - as is finding a free socket when they all need charging at the same time. But this modern hassle could be short-lived.

Instead of each device needing its own charger, it may soon be possible to recharge phones and cameras by placing them on a plastic pad the size of a mouse mat. A dense array of coils buried in the pad will transmit energy to the gadget to charge its batteries. And it will be possible to charge as many gadgets as can fit on the pad at once, the inventors say.

 

[bdewoody]

That could be done via RFID.

As far as how it's coupled - it's inductive RF. The same way a radio works.

I've built a handful of inductive chargers. It's really pretty simple in concept and has been around forever. Shavers and toothbrushes have been doing it for at least a couple decades.

The problem you'll have with vehicles is that they need a _lot_ of current to make even a dent in their battery charge. And inductive coupling just doesn't deliver that.

So the method is applicable only in low power short range usage. Still it seems better than having to have a different charger for every small battery powered device one might own.

 

[adrenalynn]

Yes and no. Now you need a different power-antenna for each device.

When all the devices standardize and build the inductive coupler into the device, then it'll be a better bet.