18650 Cell Phone Charger

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You probably would get more out of two 28650s in series and a buck circuit USB charger than a 1x18650 and boost circuit. Some of the ebay 4x18650 setups are 2x2 some are 4x1.
 
Lynx_Arc said:
You probably would get more out of two 28650s in series and a buck circuit USB charger than a 1x18650 and boost circuit. Some of the ebay 4x18650 setups are 2x2 some are 4x1.
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I'd agree with that! But then again the 1 x 18650 unit is pretty compact and can fully charge a dead phone in a reasonable time from 1 battery, so it would often be a case of 'good enough' is good enough. A better set-up may just not be needed for the majority of us.

Boost circuits can be fairly efficient:
malow said:
just measured:

Vin: 4.0v = 83% efficiency :thumbsup:
Vin: 1.2v = 48% efficiency :sick2:
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Well, efficient enough if they don't have to boost by too huge an amount. From a single NiMH cell they aren't very efficient, but from a Li-ion cell they are up near 80%. This isn't bad for a cheap boost circuit.
 
KiwiMark said:
I'd agree with that! But then again the 1 x 18650 unit is pretty compact and can fully charge a dead phone in a reasonable time from 1 battery, so it would often be a case of 'good enough' is good enough. A better set-up may just not be needed for the majority of us.

Boost circuits can be fairly efficient:

Well, efficient enough if they don't have to boost by too huge an amount. From a single NiMH cell they aren't very efficient, but from a Li-ion cell they are up near 80%. This isn't bad for a cheap boost circuit.
Click to expand...

what is the efficiency when it drops to 3.7v? If you already carry 2 18650s I would look for something that you could just put both of them in.
 
Lynx_Arc said:
what is the efficiency when it drops to 3.7v? If you already carry 2 18650s I would look for something that you could just put both of them in.
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I would guess that it would still be above 75%, for my purposes that is definitely good enough. I don't think that boost circuits are too bad for efficiency. If I have 2 18650s I may prefer to drain only one to charge my phone so that I still have a spare for one of my lights.

Everyone needs to evaluate their own needs, to some the maximum amount of charging from the minimum weight/bulk of carrying is vitally important, to others it wouldn't matter if they only got 50% efficiency as long as they could take one 18650 and fully charge a dead phone that may be all they need. For most of my camping trips I would only need a couple of phone recharges and I can easily take a couple more 18650 cells without really caring about the weight (I'm not hiking in so weight isn't a big issue).

Having said all that - does anyone have a link to a good 2s2p 18650 cell phone charger - I might consider adding one of those to my collection of cell phone chargers.
 
Lightfoot98 said:
Here you go:::::

http://cgi.ebay.com/5V-Mobile-Power...465?pt=LH_DefaultDomain_0&hash=item3cb6f30861

2S2P configuration.

Claims 95% efficiency

I have one of these also.
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Obviously you cannot use this with 1 cell or with 3 cells, but would it work fine with 2 cells or 4 cells? The other one I got that is 4p would work fine with 1, 2, 3 or 4 cells even if they aren't very well matched - obviously this 2s2p unit would be only good for fairly well matched cells, you would never want to put mismatched cells in series.

I might get 4 new cells for this unit and therefore create a ~10Ah unit with ~95% efficiency which should be good for ~7 dead to full charges (at least 6 if claimed efficiency of charger and claimed capacity of cells are anywhere near accurate) of my cellphone.
 
I would be hesitant to match parallel cells up that had considerably different voltages as this could cause the higher voltage cells to try and charge the lower cells up immediately to equalize the voltages. Once you do have them matched in voltage then that issue is not a problem any more.
 
Lynx_Arc said:
I would be hesitant to match parallel cells up that had considerably different voltages as this could cause the higher voltage cells to try and charge the lower cells up immediately to equalize the voltages. Once you do have them matched in voltage then that issue is not a problem any more.
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Yeah - they don't have to be matched, but you don't want to put a dead cell (3.3V) and a full cell (4.20) together. As long as the voltage is reasonably close it wouldn't matter if you put a 2900mAh cell and a 2200mAh cell together in parallel. In series is another matter altogether though.
 
KiwiMark said:
Yeah - they don't have to be matched, but you don't want to put a dead cell (3.3V) and a full cell (4.20) together. As long as the voltage is reasonably close it wouldn't matter if you put a 2900mAh cell and a 2200mAh cell together in parallel. In series is another matter altogether though.
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I figure within 0.3v may be ok. I wonder what sort of protection is in these to keep from overdischarging etc..
 
yeah - the single cell ones are so compact Im more likely to keep
it my backpack/car etc. I kinda like the built in light too 😉
woulda been GREAT on the airplane home from Moscow this weekend
as I was using the kindle app on my iPhone to read the new GRRM.
the flight was delayed on the runway for 2 hrs... Delta... UGH
Ill post a mini review when I get it.
 
It charged my phone just fine. Just testing out recharging them inside the unit, its a bit slow, i was getting 300ma per battery with two in there or 600ma with one. (using a 1A usb input).

I plan to charge them with my hobby charger anyway, just wanted to see its charging capabilities.

I left batteries in the unit for few days with it switched off just to check there wasnt any drain while not using it. Doesnt appear to be, they went in and came out at 3.95v.

A bit home-made looking but functioning perfectly so far.
 
A few years ago I needed a portable power source for some of my equipment. I wanted it to be fast and cheap.

I always have a lot of charged 18650's around the house so that was an easy choice.

I made a battery holder using 3/4" PVC pipe.
Originally I was going to glue all of the fittings, but just 'force fit' was good enough to hold it all together.
That also allowed me to use 3 OR 4 18650's with a quick change-out of the length of 3/4" pipe.

I took the spring-loaded terminals out of an old fuse holder and drilled the end caps to pass the wires through.

The white 'molex' connectors I've been using for lots of years for all of my power connections. So, I just made up a 12V power socket.

Now when I want to charge my cell phone, I just plug in the 12V car adapter.

The first photo shows the finished 3 x 18650 charger using a 7" pvc pipe.

The other shows the components.
When I want to use 4 X 18650 batteries I use the 9.6" pvc pipe.

http://i129.photobucket.com/albums/p213/hcir100/Radio/IMG_4309_cropped_sm.jpg

http://i129.photobucket.com/albums/p213/hcir100/Radio/IMG_4308_cropped_sm.jpg
 
Last edited by a moderator:
^^^^
wow thats really simple and awesome!
so many 12v components out there...

still waiting on my single 18650 charger.
will post back after Ive used it.
 
It's hard to think of any negatives from being in possession of a pipe with electrical wire coming out of each end attached to a cellphone . . . 😗
 
KiwiMark said:
It's hard to think of any negatives from being in possession of a pipe with electrical wire coming out of each end attached to a cellphone . . . 😗
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I had a similar thought. I'd like to see someone try and get that through airport security :thumbsup:
 
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