Inductive battery charger

Thread Starter


Joined Jan 16, 2008
My circuit will be housed in an immersible plastic container, so I need some way of charging the battery without opening the container. Can someone point me to some material that describes how to build an inductive battery charger?

The circuit will use a Lithium Polymer 1000ma battery and a MAX1555 charging device. However, I don't have a clue about what inductors to use and the most efficient AC frequency.

Does anyone have any experience with this?



Joined Dec 27, 2007

The only experience I have with this is my electric toothbrush. It might be a bit costly to rip one open, but it would be fun to see.

Basically, you want to create a transformer to couple the energy between your source and the circuit inside the plastic container. The toothbrush has a base which contains the primary and the toothbrush sits cylindrically around this piece. I suppose it is a good way to couple the field.

I suggest that you grab some iron and magnet wire of various gauges, then experiment. Otherwise, you'd need to model this as a transformer with an airgap, etc. If you're interested in an analytical method, look up "how to draw magnetic circuits". If you're into Finite Element modeling, you can play with that to figure it out. If you need an optimal solution, approach it analytically. If you just need something to work, maybe not so well, then just mess around with a signal generator and a scope.