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"Nuke" Recharging of Portable Devices

Battery Low ? Pop it in the microwave and set to "Cellphone"
  (+13)(+13)
(+13)
  [vote for,
against]

More ubiquitous than an induction recharger is the microwave oven: every home and office has at least one.

The idea is to build the covers of portable devices, such as cellphones, PDA's, media-players etc, with an embedded rectenna, arranged as a Faraday cage around the circuitry, which will not only soak up the microwaves to recharge the batteries, but simultaneously protect the delicate'ish electronics inside.

FlyingToaster, Jan 07 2011

Power Microwave Diode http://www.google.c...fp=ea5733a97aebfa72
Rudimentary search [csea, Jan 08 2011]

Campfire Cellphone Charger http://boards.strai...x.php/t-559862.html
Similar thought... [csea, Jan 08 2011]

Wireless charging via microwave energy http://www.seminarp...rowaves-full-report
.pdf requires account [csea, Jan 08 2011]

[link]






       This is either an outstandingly brilliant idea or a very very bad one, but I'm going with the first option. [+]
MaxwellBuchanan, Jan 07 2011
  

       More ubitiqu ubig ubqutui you be quiet ubweek commonly found is a kettle.
Ian Tindale, Jan 07 2011
  

       [Ian] are you all right?
Voice, Jan 07 2011
  

       /Ian/ when he got to the quit in ubiquitous, he did.
bungston, Jan 07 2011
  

       Yes, [Voice], had it not been in text it would have been cause for concern. As it was in text it is instead a rather funny comment. And then [bungston] came through with the zinger.   

       2.5
rcarty, Jan 08 2011
  

       Won't the process of charging the phone reduce the faraday effect and subsequently shit the phone? I'm guessing there's a safe middle ground and it just may be worth it. +
daseva, Jan 08 2011
  

       The phone wouldn't actually be bothered by the electric field (or else induction charging would hardly work), and microwave transmission method efficiency is listed as 95% so there wouldn't be enough microwaves getting through to poach it. (As a sidenote, induction charging has an efficiency of ~85% at best.)
FlyingToaster, Jan 08 2011
  

       [csea] relevance of your link ? [edit: oh I get it]
FlyingToaster, Jan 08 2011
  

       Sounded fairly simple, just provide a tuned antenna and a microwave diode to rectify the energy to dc. (+)   

       But I'm quite skeptical that this could work. ( I did a preliminary search for an appropriate microwave diode to rectify the oven field. [link] -Not much success.)   

       I'm fairly sure you'd be better off converting uwave radiation to thermal energy (heat) and then converting to electrical current. Protecting the phone via Faraday cage might upset the oven's field.   

       Efficiency shouldn't be a concern; even low-powered uwave ovens deliver a few hundred Watts, and a phone charger only needs maybe 10W.   

       A thermally-based charger would work with [IT]'s ubqwtrr-whatever kettle. [and campfires! -link]   

       A bit outside my expertise, would be glad to learn more.
csea, Jan 08 2011
  

       But efficiency *is* the concern, not from a cost/kWh perspective, but from the perspective of: whatever power *isn't* being sopped up is going places you don't want it to, ie: frying the guts of the phone or, as you mentioned, upsetting the microwave oven itself. That's where the "95% efficiency"(WP) comes in handy.   

       That being said, I wonder if you could make a charger-free cellphone, utilizing ambient celltower radiation to power transmission and for receiving go unpowered... nah, probably not, you have to have power for AD/DA stuff and en/decoding. § x1
FlyingToaster, Jan 08 2011
  

       Which is why a thermally-based product may be the solution - i.e. let the oven do what it is designed to do (produce heat) and let the charger take an inefficient fraction and convert to charging current.   

       Sometimes, it's best to let stuff do what it was designed to do...
csea, Jan 08 2011
  

       [csea] Thermal charging sounds neat too except you'd have to worry about overloading the thermal capacity of the cellphone construction materials. Given an efficiency of 95%, a "beamed power" method is going to take less magnatron on-time = less heat/emf to dissipate. So thermal charging is probably not a good idea in a microwave.   

       On the other hand if it was strictly thermal, you could dunk your cellphone in your coffee to recharge... but thermal recharging requires a cold side, so that won't work unless you have someplace to dissipate the heat.
FlyingToaster, Jan 08 2011
  

       //Sometimes, it's best to let stuff do what it was designed to do...// [marked-for-tagline]
rcarty, Jan 08 2011
  

       The inside of the oven would be a suitable heat sink for the few Watts needed. (Not my bone.)   

       Another approach would be to drill a suitably sized hole in the microwave, and use a "2.45GHz slotted wave guide antenna" and presumably a suitable rectifier. (Don't try this at home!) [link]
csea, Jan 08 2011
  

       And forget about making any phone calls on cordless phones or using any bluetooth or Zigbee devices.
Ian Tindale, Jan 08 2011
  

       //and use a "2.45GHz slotted wavelength antenna// which is what we'll be using as a Faraday cage in this Idea. (okay, it's a pretty special Faraday cage since the wires aren't joined to each other as a mesh). Sry about the autobone accusation.
FlyingToaster, Jan 09 2011
  

       [21Q] The Idea uses a rectenna which is folded through the cover such that it also acts like a Faraday cage, ie: the wires are spaced closely together.   

       The "metal in microwave" thing won't happen: these wires *absorb* the uwaves because they're a microwave antenna: that's what they do. So there's no bouncing the uwaves back to the magnetron.
FlyingToaster, Jan 09 2011
  

       because I thought I'd be cute and push "Faraday Cage" as an easy visual aid... consider me chastised, post amended.
FlyingToaster, Jan 09 2011
  

       There's a shop in East Anglia that sells batteries.
MaxwellBuchanan, Jan 09 2011
  

       I've heard of that place: do they deliver ?
FlyingToaster, Jan 09 2011
  

       If you’ve got somewhere to put all those hens, yes.
Ian Tindale, Jan 09 2011
  
      
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