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Thread: 18650 Cell Phone Charger

  1. #1

    Default 18650 Cell Phone Charger

    I'm looking for a device that charges the small lithium batteries in portable electronics from 18650 standard cells. I've searched high and low for such a thing, but never found one that does exactly that. There a AA-powered things that don't work very well, and large packs that cost $100+ and are intended for laptops and portable dvd players, but no simple thing that will charge a cell phone or iPod from an 18650.

    This one comes close, but I don't get the impression the cells are removable - a fatal law for a flashaholic.

    http://www.goldengadgets.com/1-watt-led-flashlight-2200mah-usb-power-charger.html


    So has anybody found anything better? If not, can somebody build this? I know I'm not the only one who would purchase such a device.

  2. #2

    Default Re: 18650 Cell Phone Charger

    Hey, I've been looking for the same thing!




  3. #3
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    Default Re: 18650 Cell Phone Charger

    Browse "Chargers" (under the "Electronics" section) over at the DX website you will find several of these devices. They use everything from AAA, AA, prismatic Li-Ion to Solar for a power - no 18650's as far as I can tell though.

  4. #4

    Default Re: 18650 Cell Phone Charger

    Yeah, as I wrote, there are preassembled packs and AA/AAA options, but I would really prefer something that would allow me to use my current stock of 18650s. My experience with the AA versions is that they don't pack enough punch, and I'm hesistant to carry around a lithium pack containing cells of unknown origin and quality.

    So how about it? Somebody willing to frankenstein a cheap 1x18650 or 2x18650 flashlight body with an appropriate circuit board for charging? Maybe an LED or two to provide battery status, etc?

  5. #5
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    Default Re: 18650 Cell Phone Charger

    just get the eneloop mobile booster, it will work safely for you and is the best in the market.

    though i never bought from DX before but from the catalog i could tell 90% goods sold there are china made garbage.

  6. #6
    Flashaholic balou's Avatar
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    Default Re: 18650 Cell Phone Charger

    http://www.dealextreme.com/details.dx/sku.17470
    Looks like it can be opened.
    That's actually quite funny... a Li-ion based li-ion charger.
    Unfortunately, upconverting to 5v and then using that to recharge a li-ion is rather inefficient. It wouldn't surprise me if cell phones used a linear regulator to bring the 5v back down to 4.2v (and why should they bother using switching regulator - the charging power usually comes from mains, where that 16% efficiency hit won't make any noticeably difference)

    Something like that:
    http://www.dealextreme.com/details.dx/sku.21806
    powered with Li-ions would be nice. In case you don't get it (I didn't either at first sight): you clip your cell phone battery into it, and align the springs to touch the contacts on your battery.
    That could probably be made to be >90% efficient

    Quote Originally Posted by TranceAddict View Post
    though i never bought from DX before but from the catalog i could tell 90% goods sold there are china made garbage.
    Highlights added...

    First, aren't >95% of all electronic products chinese made garbage?
    Second, how can you tell if you never ordered on DX?

    And yes, some products on DX really are crap, and they don't have very strict QC... but in the end, you'll still save lots of money buying from DX - you cut out all the middlemen. I saw a flashlight in a local supermarket chain for about $15 - on DX the exact same flashlight is $4.40.
    And you can usually tell the crap from the good products on DX - they allow uncensored discussion of products, and they pull products if several people complain.
    This space intentionally left blank

  7. #7
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    Default Re: 18650 Cell Phone Charger

    Quote Originally Posted by SnowplowTortoise View Post
    This one comes close, but I don't get the impression the cells are removable - a fatal law for a flashaholic.

    http://www.goldengadgets.com/1-watt-led-flashlight-2200mah-usb-power-charger.html

    In the pictures it says "Battery replacement designed" on the front of the package, about dead center. I'm not sure what all that could entail though.
    <bunch 'O flashlights>

  8. #8
    Flashaholic balou's Avatar
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    Default Re: 18650 Cell Phone Charger

    Quote Originally Posted by Kremer View Post
    In the pictures it says "Battery replacement designed" on the front of the package, about dead center. I'm not sure what all that could entail though.
    Look at the first link in my post above yours
    This space intentionally left blank

  9. #9

    Default Re: 18650 Cell Phone Charger

    So it does appear that you can replace the cell. In the description at the link I first posted, they mention the "build in battery" (sic), which didn't sound replaceable to me. That's better, though it still looks pretty rickety to me - at least compared to the aluminum flashlight host I was imagining. But whatever - I will consider that a viable option, especially at $20. And I agree with Balou - 2 cells would seem to make for a more efficient set-up - with the juice flowing downhill as it likes to do.

    Still, I'm a little disappointed by the weak showing of Can-Do posts. Where are the McGuyvers? Where's the maker-spirit that drives us to spend countless hours trying to build some goofy, unfinished contraption that we could easily purchase Hong-Kong direct for half the price? I buy enough of life's necessities off the shelf. This is a hobby for me, and as such I would rather make more and consume less. Just my perspective though.

    P.S. Balou - XKCD is the best!

  10. #10
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    Default Re: 18650 Cell Phone Charger

    Quote Originally Posted by balou View Post
    Look at the first link in my post above yours
    Doh....


    I had also been looking for something like this for a while, and it looks like it will double as an 18650 charger when plugged into a PC or other USB power supply. I quit looking for a mobile 18650 charger though after I got my new Dell laptop. It has this 'USB PowerShare" feature where a certain USB port on it remains powered, even with the laptop off, to charge devices. There are nine 18650's in the laptop battery, which will charge a whole lot. The laptop isn't exactly pocketable though.
    Last edited by Kremer; 12-10-2009 at 02:33 PM.
    <bunch 'O flashlights>

  11. #11

    Default Re: 18650 Cell Phone Charger

    Home Depot is now selling what appears to be single 18650 cell lithium tools. They have a "USB power supply" in their kit. Of course, they have wrapped their batteries in a plastic case with a protection circuit, but if you are decent at modding, you could likely open up the case and use your spare batteries.

    If your device can charge from a standard USB port this looks like it would get you started.

  12. #12
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    Default Re: 18650 Cell Phone Charger

    I did a big search for the same thing as my
    phone/GPS's all have the mini USB port.

    Also i wanted a longer power cord so you can
    leave the battery in your pocket while
    using your device.

    Ordered these
    http://www.kaidomain.com/ProductDeta...ProductId=9855

    Hopefully arrive next week.
    Cheers
    Dom

  13. #13
    Flashaholic* QtrHorse's Avatar
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    Default Re: 18650 Cell Phone Charger

    Let us know how they work dom. This would be a nice option for an emergency.

  14. #14

    Default Re: 18650 Cell Phone Charger

    Don't buy sku.17470; sku.18883 is the same thing but cheaper.

    WRT efficiency, yeah, it occurred to me that Li-ion -> 5V -> Li-ion has got to be pretty bad, a 2-cell version with buck converter (and of course balanced or independent charging) would be better, but it's not like I use it much, and when I do, 50% efficiency is good enough -- still much better than no charging ability!

    But just think of the overall efficiency if you use this thing's USB charging capability -- which is probably not especially efficient.

    Anyway, the nicest thing about this charger, according to most people I've showed it to, seems to be the flashlight head. It does indeed deliver quite a nice beam (TIR optic, so no surprise there), and decently bright. But while I haven't taken any measurements, the notion of regulating up to 5V to run a 3.5V LED makes me shudder -- though I haven't taken any measurements, I can't help thinking even the worst of my 18650 lights would be more efficient, so I almost never use it.

  15. #15
    Flashaholic* csshih's Avatar
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    Default Re: 18650 Cell Phone Charger

    i have the device mentioned by the OP..
    ..it'll charge my ipod from empty to ~80% on a 2200 cell..
    NOTE: only unprotected cells fit

  16. #16
    Flashaholic* Fallingwater's Avatar
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    Default Re: 18650 Cell Phone Charger

    Quote Originally Posted by SnowplowTortoise View Post
    Still, I'm a little disappointed by the weak showing of Can-Do posts. Where are the McGuyvers? Where's the maker-spirit that drives us to spend countless hours trying to build some goofy, unfinished contraption that we could easily purchase Hong-Kong direct for half the price? I buy enough of life's necessities off the shelf. This is a hobby for me, and as such I would rather make more and consume less. Just my perspective though.
    Well, since we're both DIYers, here's my two cents...

    Ditch the charger altogether. The LiIon->USB->LiIon conversion is bound to waste a significant amount of power.

    Crack open the gadget whose runtime you want to increase, get at its cell and put a tiny three-terminal switch across the cell output before it gets to the monitoring circuit. To the other pin of the switch attach one of the two wires leading to a suitable connector (I'm in love with JST ones available at DX for this sort of job - they are small, unobtrusive and easy to use). The other wire, you just connect in parallel to the existing cell.
    This way you have a gadget that works fine off its own cell, but to which you can connect any other LiIon cell via JST connector, flip the switch and have it use the external cell directly - no power lost in conversion.

    This obviously won't do if you don't want an external cell hanging from your device (or in a holder attached somehow to said device); on the other hand, you can attach any LiIon at all - 14500 from a flashlight, prismatic cell from any trashed gadget, big fat LiPo leftover from the RC plane that you nosedived on concrete...

    Depending on the device, it might work fine off a 4xNiMH battery too (3xNiMH won't do for a LiIon-powered gadget; it'll think the battery is empty almost immediately due to voltage incompatibilities).
    Eat, drink and be merry, for tomorrow you may die.

  17. #17

    Default Re: 18650 Cell Phone Charger

    I like Dom's suggestion - that looks about as simple and cheap as it gets. But way too easy!

    Which brings me to Fallinqwater's post. I can just picture it - my brand new Droid, sleek and aerodynamic, and an 18650 holder hot glued to the back like a Ferrari towing a U-Haul. I love it! I may have to try that if my original idea doesn't pan out.

    I found this IC from National Electronics. I honestly have no clue what most of the specifications mean, but it appears that it will output 5V at 500ma from a 2xLi-ion source with at least 90% efficiency. Can anyone tell me if I would need more stuff to make this work? Seems like driver boards tend to have more than one doodad on them. Anyway, if I can get the right regulator, I will try to fit it inside this cheap 2x18650 host, and run a wire out somewhere with a female USB plug. So it should work as a light and a cell phone charger. We'll see.
    Last edited by SnowplowTortoise; 12-14-2009 at 08:48 AM.

  18. #18
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    Default Re: 18650 Cell Phone Charger

    The LM22671 will require several external components (including an inductor) and a means to wire it all together.

    This is what I use http://search.digikey.com/scripts/DkSearch/dksus.dll?WT.z_header=search_go〈=en&site=us&keywor ds=507-1384&x=0&y=0

    It will operate with 4.5V-13.8V input and has an adjustable output from 0.591V-5.1V (set with a single resistor) at up to 10A. Efficiency is 91% at 5V output and it measures just 16.51 x 10.41 x 8.13mm.

  19. #19

    Default Re: 18650 Cell Phone Charger

    Thanks rmteo - that sounds perfect. I apologize for my ignorance, but can you please confirm some assumptions about the hook-up?
    1. If I want 5V out, I don't need to connect anything to the TRIM pin, right?
    2. If I want it to be always-on, I just connect the ENABLE pin to GND?
    3. If it is capable of delivering 10A, is it a problem that this is much greater than the USB specification of 500mA max? I wouldn't think so, but I would prefer to hear that from someone who knows what they are talking about.

  20. #20
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    Default Re: 18650 Cell Phone Charger

    1. For 5V out, you need to connect a 268K (or closest standard value) resistor between TRIM and GND according to the formula RTRIM = 1.182/(Vout-0.591) kOhms.

    2. If the ENABLE pin is held low, the unit is off (it must be >2V and <5.5V to turn the unit ON - I believe the default is ON).

    3. It is capable to delivering up to 10A, but you should limit your application to under 500mA to stay within USB specs. No problem here.

    BTW, they also make a 3A and 6A version - although at $9, I think the 10A is the best deal.

  21. #21

    Default Re: 18650 Cell Phone Charger

    For the money you'll spend and the bulk of the batteries and charger, why not just buy a bunch of the $5 chinese replacement batteries for your phone and carry them with you to swap out? I've been using them for three different phones and they work fine. The oem are usually made in china too so it's not like you lose much quality.


  22. #22

    Default Re: 18650 Cell Phone Charger

    Quote Originally Posted by C-Beam View Post
    For the money you'll spend and the bulk of the batteries and charger, why not just buy a bunch of the $5 chinese replacement batteries for your phone and carry them with you to swap out? I've been using them for three different phones and they work fine. The oem are usually made in china too so it's not like you lose much quality.

    Versatility -- I already am carrying two different devices that use the same charger (N810 and cellphone), but different batteries, and one 14670 and at least one 18650 flashlight. I'd much rather add a couple 18650 or 14670 spares that can be used for any of several devices rather than an extra stash of batteries for each Nokia.

  23. #23

    Default Re: 18650 Cell Phone Charger

    I have been considering some ideas to maximize efficiency. I want to charge my batteries using solar panel in backcountry.

    Solar panel:MP7.5-150 Flexible Solar Panel 7.2V @ 200mA
    http://www.flexsolarcells.com/index_...2_MP72_150.php

    IC:LT3650
    http://www.linear.com/pc/productDeta...1,C1089,P88675

    Battery:
    Instead of solar panel-buck>18650>boost-5V>mobile battery,

    I am thinking of charging a spare battery and then simple replacing it in the phone.

    My plan is to use the same battery in DIY headlamp.

  24. #24
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    Default Re: 18650 Cell Phone Charger


  25. #25

    Default Re: 18650 Cell Phone Charger

    Quote Originally Posted by schmart View Post
    Home Depot is now selling what appears to be single 18650 cell lithium tools. They have a "USB power supply" in their kit. Of course, they have wrapped their batteries in a plastic case with a protection circuit, but if you are decent at modding, you could likely open up the case and use your spare batteries.

    If your device can charge from a standard USB port this looks like it would get you started.



    FWIW: I bought the $99 kit this morning; it comes with two batteries, a single charger, drill, cutter, flashlight, and ear muffs that block loud noise (but didn't work because I could hear my wife loud and clear), and an adapter that'll let you use the battery to charge up via USB.

    I haven't had a chance to play around with it yet but I thought it was a bargain. BTW, extra batteries are about $12. They sure could be 18650s but I wouldn't know unless I cracked open the plastic case.

  26. #26

    Default Re: 18650 Cell Phone Charger

    If I make a pack using 4 NiMH, do you think I need any regulation at all? If the USB standard is 5V, and the phone can charge from USB, I wonder if a +/- 1V swing is close enough.

    I'm still interested in the 18650 version, I just noticed I have an abundance of sub-C's laying around and thought I might put them to use as well.

  27. #27
    Flashaholic balou's Avatar
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    Default Re: 18650 Cell Phone Charger

    Probably won't work well.
    USB spec says 4.75-5.25V - normal tolerances are 10%, but USB has only 5% tolerance.
    NiMH batteries under load have 1.2V, giving you 4.8V.

    There are some cellphones who even need 5.5V or 6V to charge properly (DX even sells a 5V to 6V upconverter in usb dongle form).

    If you want to use sub-Cs: a quick and easy way would be using 6-8 cells and an LM7805 voltage regulator. It's a linear regulator, so it will waste the excess voltage as heat, but its extremely easy to build
    See page 22, figure 7: http://www.fairchildsemi.com/ds/LM%2FLM7805.pdf
    It's just the IC and two capacitors, and you could probably build it without the caps, or gut some out of an old radio etc (it says 0.33uF and 0.1uF, but pretty much anything in the range of 0.1-10uF will do). The 7805 also has internal thermal shutdown and overcurrent protection - this chip is nearly unkillable.

    edit: addendum about the caps: Ci is only needed if the leads to the chip are long enough. I'd say no if you keep the leads shorter than 5cm/2in. Co is for better output stability - a charger normally has constant current, so this isn't needed also.
    So that means you only have one chip with three legs - 7-30v input, ground, and 5v output.
    Last edited by balou; 12-21-2009 at 02:36 PM.
    This space intentionally left blank

  28. #28

    Default Re: 18650 Cell Phone Charger

    Ah, too bad. 6-8 sub-C's is starting to get pretty bulky. I guess I will set them aside for some future project. Thanks for the info.

    So, back to the 18650 approach. I had found this pre-built board:
    http://www.batteryspace.com/dc-dcreg...dc1ampmax.aspx
    Why does it appear to be so big and full of stuff, when the circuit you described is just a little IC and 1-2 capacitors?

  29. #29
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    Default Re: 18650 Cell Phone Charger

    Just an update on the Kaidomain charger.

    1. It works :-)

    2. 5.53V out (the back of the unit says 5V 500mA).

    3. When plugged into my computer USB - 4.33V 243mA.

    4.Trustfire protected 2400mAh 18650 is a tight fit.
    AW 2200mAh 18650 protected is nice fit but a rubber band or something would be
    needed to stop the battery from falling out in your pocket.

    My phone is half empty so i'm using the unit now -no smoke so far :-)

    Cheers
    Dom

  30. #30
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    Default Re: 18650 Cell Phone Charger

    Quote Originally Posted by dom View Post
    Just an update on the Kaidomain charger.

    1. It works :-)

    2. 5.53V out (the back of the unit says 5V 500mA).

    3. When plugged into my computer USB - 4.33V 243mA.

    4.Trustfire protected 2400mAh 18650 is a tight fit.
    AW 2200mAh 18650 protected is nice fit but a rubber band or something would be
    needed to stop the battery from falling out in your pocket.

    My phone is half empty so i'm using the unit now -no smoke so far :-)

    Cheers
    Dom
    Please keep us updated . . . I'm very interested to get your opinion on the device.

    Francis

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