Inductive charging 1xAA NIMH light

[sparkysko]

I hate unscrewing my lights to replace/recharge the batteries, so I don't change them as often as I should. Then I got to thinking of charging solutions, and pretty much determined it would be pretty difficult/impossible to retrofit most small 1xAA lights with a charging jack, or, even if I did manage to put a jack on them, it would decrease the reliability of the light.

After ripping out the protection circuit on a dead li-ion cell, I became fascinated with the form factor, then it dawned on me.

Why not put a small coil and diode on the end of a NIMH battery, just like a Li-ion protection circuit board. In case you haven't ripped one apart, it's a small PCB that sits on the negative end of the li-ion cell, and has a thin braided strap that goes to the positive side (Which is insulated from the casing).

Then you put the flashlight with the battery on your inductive charging pad and voila. I still have no idea about how to figure out current requirements, etc in regards to coils, but I found something similar that's proof of concept.

http://www.afrotechmods.com/fuxx0red/mouse/mouse.htm
http://www.afrotechmods.com/cheap/arnoldpad/arnoldpad.htm

 

[Jumi]

Most led lights allready has coil in them so the original circuit probably would not like the charging
But could the circuit be design so that it could also charge the batteries in the light?

Juha

 

[Foxx510]

You could get one of the inductive charging electric tooth brushes and mod it into a flashlight.

 

[TooManyGizmos]

Are inductive charging pads in common use now ?

I don't think so yet .

 

[Flash_Gordon]

How is going through all of that easier than just putting your cells on a charger? You will loose the use of your light for many hours while it sits in your inductive charger.

Would not work at all on a metal body light.

Mark

 

[Tohuwabohu]

Sanyo eneloop lamp, interior light and "flashlight" with contactless charging system .

http://www.candlepowerforums.com/vb/showthread.php?t=235466

 

[Ardillakilla]

And here I am modding my C9000 to charge my electric toothbrush whose inductive charging results in suboptimal performance. I was also thinking of replacing the battery with a li ion and/or adding a charging jack.

 

[AnAppleSnail]

And here I am modding my C9000 to charge my electric toothbrush whose inductive charging results in suboptimal performance. I was also thinking of replacing the battery with a li ion and/or adding a charging jack.

As a side note, I bet a UV light would kill germs very effectively in there .

I think you could do it as long as the flashlight didn't have metal near where the charge coil is...but I don't know the EM physics to really help much. I bet that it could be put into a LEGOable tailcap, though charge time may be slow.

 

[sparkysko]

Well, I had typed of a writeup, but it got deleted before posting.

Here's what I found.

At 3 volts AC, 80 microhenries equals about to 100ma of current from 'inductive resistance'. You'd need a matching coil on the battery. With any reasonable sized wire, you couldn't get 1/100th of this much inductance on the end of a battery. So you wouldn't be able to easily create such a thing sticking only on the end of the battery. I'm sure you could use magnet wire and wrap around the battery itself. Checking clearance, I'm sure you could just wrap magnet wire around a cell and have it still fit in a battery tube.

As far as the tube on the cell blocking the inductance. I made a grounded faraday cage out of aluminum foil. It blocked RF, but it didn't block the magnetic portion of RF (FM was blocked, however AM with a ferrous coil antenna still went through).

 

[sparkysko]

Alrighty. Hoping we don't electrocute ourselves.

A buddy is going to come over and we're going to try to rig up something.

We have a 6 volt 300 ma wall wart, we're going to short out the diodes and capacitors, so it's just a 6 volt AC wall wart. Then we're going to connect a radio shack "RF Choke" which is a 100 microhenry inductor, and then have it go off to another RF choke which will be on the battery side with a diode attached.

If this works, then we can do the math to make a flat inductor coil, and wire wrap the battery.

 

[65535]

Someone mentioned it, and it just occurred to me, a metal flashlight body makes a decent faraday cage around the flashlight greatly reducing the amount of EM energy that can penetrate the case to a charging coil.

 

[VidPro]

Are inductive charging pads in common use now ?

I don't think so yet .

they have a charge pad that you could say finnaly works, but it isnt inductive at all, it uses metalic strips in a grid, the items to be charged are fitted with contact points that line up with the grid, no mater how it is placed on the grid. then to finalise it, they have "Pucks" that wire out to your devices that dont have the contacts adapter, the pucks connect to the grid, and a WIRE still goes to the device.

they have various contact adapters for phones, so far, that connect to the battery or the charging port, and put the contact points on the back of the device.

its more like a multi docking , you could say, but because of the connection grid, and the correctally spaced connection points, you can toss it on the "pad" anywhere and it should make a connection.

i was so impressed, i got a bigger battery for my devices :laughing: soes i dont have to charge them as often.

http://www.mobilewhack.com/duracell-shows-off-mygrid-wireless-charging-pad/
durasells version

http://www.mobilewhack.com/nokia-to-offer-new-phone-charging-method/
nokia touching on induction , , , 5 milliwatts oooooooohhh, just dont get a call ok

http://www.gizmosforgeeks.com/2009/04/23/video-demos-of-ecoupled-wireless-charging-tech/4483
fultons E-coupled Video demo from CES, reminds me of the inductive stove, which wasted 50% of its power


http://www.wildcharge.com/
the pad i was originally referring to,, Wire Free? ok whatever

http://www.youtube.com/watch?v=_iFqAYvJI2g
One day your WHole house will be powered by , , , Dreams while i am putting switch offs on wall warts to save 40picowatts, they will be blowing out 50% of all thier charging power.

 

[sparkysko]

Well, a 6v 300ma wall wart doesn't produce anywhere near enough power. Voltage drops to 0.1 volts @ 1 amp at the transmitting coil. Almost non existent power at the receiving coil.

Tried several coils everywhere, no love. Eventually just plugged the coil into 110 AC on a 500w power inverter. It would briefly light up an LED attached to another coil (as a test) before the inverter would overload and shutoff. Unsure how much current it'd draw, we plugged it into mains power (With adequate protection), almost immediately tripped the breaker in my power strip.

Soooooo, not easy!

 

[HKJ]

Well, a 6v 300ma wall wart doesn't produce anywhere near enough power. Voltage drops to 0.1 volts @ 1 amp at the transmitting coil. Almost non existent power at the receiving coil.

Tried several coils everywhere, no love. Eventually just plugged the coil into 110 AC on a 500w power inverter. It would briefly light up an LED attached to another coil (as a test) before the inverter would overload and shutoff. Unsure how much current it'd draw, we plugged it into mains power (With adequate protection), almost immediately tripped the breaker in my power strip.

Soooooo, not easy!

Try using a 100mH coil (not uH), that would work much better at 60Hz.

 

[sparkysko]

Duh, micro vs milli. I overlooked that.

Well, a 100mh inductor is impossibly large, so I guess you'd need to use more than 60hz to shrink the size down. Oh well.

 

[HKJ]

Duh, micro vs milli. I overlooked that.

Well, a 100mh inductor is impossibly large, so I guess you'd need to use more than 60hz to shrink the size down. Oh well.

Next time try my electron calculator, it is very useful when playing with electronics at least if you know the basics.

100mH is not that difficult to make, it is about 1000 turns of 0.3mm wire:
Turns: 1.09k

Inductans: 99.96 mH

Coil length: 5 mm
Avg. coil diameter: 65.34 mm (50 mm .. 80.68 mm)
Winding thickness: 15.3 mm

Wire length: 223 m
Resistance: 53 ohm (copper wire at 20°C)
Estimated mass: 141 g (of copper wire)

This would not fit in a flashlight, but would be fine for a transmitter coil.