Wireless battery charger ?

[F117]

Just an idea to maybe plant a seed in someone's head...
More and more portable electronic devices have a coil on board intended for wireless battery charging.
E.g. Vishay offers a wireless charging coil - flat spiral - for charging of 5V portable electronics.
Inductance is 10.7 microHenry at 200kHz.

Since most MDs have some kind of search coil, it would be easy if the coil could be used in a reverse way to charge the batteries.
Just place the detector on the charging plate - maybe flip a switch to connect the search coil to the charging electronics - and leave it like this overnight.
The coil picks up the AC field - e,g, 10 kHz - and feeds it to some rectifier - charger - .... to (trickle - ) charge the batteries while not in use.

Forgive me if this topic has already been discussed, but I couldn't find any references searching for "wireless & charger".

Any ideas if this would be feasible and how ?

regards,
- Bernard

[Skippy]

There isn't much to a wireless charger coil, it's probably simpler to have a seperate coil. A cheap source of the bits needed for experimenting could be a cordless toothbrush. There are a few articles online about cordless charger hacking, worth reading.

[F117]

Skippy,
thanks for your input.
I know how wireless charging works.
That is why it would be very cool to reuse the parts that are already there, mainly the coil, and in the evening you just place the MD on its charger plate, flip the switch to disconnect the coil from the MD and connect it internally to the charger and leave it there overnight.
With my XP Goldmaxx power, I have to disconnect the coil connector and connect the external charger instead.

[Skippy]

For me, it would be an inconvenient solution, as I disconnect the coil from the main-box and dismantle the three-piece stem to pack my machine in a bag after use. So I would have to partly re-assemble it in order to use the coil as a charge pickup device. I also have different sized search-coils, which would make things more complex.

[golfnut]

This can be done, sure its just a transformer when on charge coil


It may be tough to get CE mark, etc due to emissions.


I would do this idea on the Rx coil as you will need TURNS.

You would need to make the Rx circuit circuit isn being powered partially by juice from the tx coil during charge - or you would leak energy as you charge.


Sure good idea, You would save the contacts getting corroded off from the chemicals they put on the feilds as contact less



I have an idea for a det, why cant you play your music through them, say off a micro SD - music gets dubbed over when u get a hit. Simples.


S

[bernte_one]

hello
i think that charging via induction isnt efficent enough
a big part of the energy will be lost while transmitting

but it is a way to do charging at some under water detectors
as i can remind ebinger has a line of security handheld detector with wireless charging station (like the electric toothbrush)

regards

[F117]

This is a link to the datasheet of the RX coil of the Vishay wireless charger:

http://www.vishay.com/docs/34338/iwas3827.pdf

Looks very similar to a PI planar monocoil ?

[homefire]

Look up Pace maker Battery Chargers.

[peterr88]

This is a link to the datasheet of the RX coil of the Vishay wireless charger:

http://www.vishay.com/docs/34338/iwas3827.pdf

Looks very similar to a PI planar monocoil ?

thank you

[bklein]

I am playing with these at work right now. TI and IDT both have development kits. Mouser sells the Wurth coils. TDK makes some nice coils as well as a charger module for a phone. These things are focused on a choice of input voltages for the charger - 19V/12V/5V. The receivers are focused on 5V 1A out. IDT seems the most advanced at this point as their designs have less component count. The concept is based on the TX pinging for a RX platform, then it goes into high power mode with intercommunication between the two. There are ferrite plates on both platforms to try and minimize spurious emissions. Some have strong magnets for centering purposes - these can screw up sensitive nearby electronics. The technology seems still progressing as there are issues with NFC (big coil too). I imagine at some point wireless charging and NFC will share the same setup - but for the most part right now they are separate. I don't really see the point of charging a battery unless you really cannot get access to the battery contacts - and that would usually mean the battery is inside a case/product. Our batteries are usually field replaceable so then the contacts are available and better used.

[F117]

A very simple test for wireless energy transfer from the MD coil - in the opposite way of the concept of a wireless charger:
- take a small coil from a 12V/5V relay
- solder a high-bright LED to the coil terminals - polarity doesn't matter
- keep the coil in the vicinity of your MD"s coil

In case of my XP Goldmaxx Power, the right coil is clearly the TX side.

You could of course use this as extra illumination on a dark field...

kr ,
- Bernard

[ODM]

Air cored coils are generally ineffective for energy transfer purposes. Those inductive chargers usually have ferrites etc. for flux control purposes, and to keep transferred power sufficiently high for reasonable charging times.

What would be the purpose of this wireless charger? Full hermetic sealing? There are often better ways around it, such as sealed charger terminals. Also, adding power harvesting to the search coil adds another source of grief for designing sensitive frontends.

Not to say it shouldn't be done, but there are often easier ways around the initial reasons

[Midas]

You could actually use something out of shakeNcharge torch, ie just a magnet that moves around inside a coil. No need to even have a battery. As you wave the detector around it harvests some of kinetic energy and uses it to energize the MD coil. I hope this actually is as impractical as it sounds.... I hate giving away million dollar ideas. :P

PS: If anyone actually designs one, I'd like 1c per unit. Thanks.

Midas