18650 Cell Phone Charger

[SnowplowTortoise]

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.

 

[curtispdx]

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

 

[rmteo]

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.

 

[SnowplowTortoise]

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?

 

[TranceAddict]

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.

 

[balou]

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

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.

 

[Kremer]

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.

 

[balou]

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

 

[SnowplowTortoise]

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!

 

[Kremer]

Look at the first link in my post above yours

Doh....:duh2:


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.

 

[schmart]

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.

 

[dom]

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/ProductDetails.aspx?ProductId=9855

Hopefully arrive next week.
Cheers
Dom

 

[QtrHorse]

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

 

[Benson]

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.

 

[csshih]

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

 

[Fallingwater]

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).

 

[SnowplowTortoise]

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.

 

[rmteo]

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&keywords=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.

 

[SnowplowTortoise]

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.

 

[rmteo]

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.