18650 Cell Phone Charger

[C-Beam]

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.

 

[Benson]

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.

 

[Huz]

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...s/pages/Flex_Cells_Individual_12_MP72_150.php

IC:LT3650
http://www.linear.com/pc/productDetail.jsp?navId=H0,C1,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.

 

[Lightcrazycanuck]

 

[curtispdx]

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.

 

[SnowplowTortoise]

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.

 

[balou]

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/LM7805.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.

 

[SnowplowTortoise]

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-dcregulatormodulefrom60-84vdcto5vdc1ampmax.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?

 

[dom]

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

 

[PurpleDrazi]

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

 

[SnowplowTortoise]

Alright, please keep the laughter to a minimum. This is not what I envisioned when I first began, but I guess it's what you get when you cross inadequate tools with a superficial understanding of electricity and total lack of preparation or patience. Here is my first attempt at an 18650 cell phone charger.



The plastic box is from Radio Shack. As recommended by Balou, I used the LM7805, which is a linear voltage regulator. It must not be terribly efficient because it gets really hot in use. I had to attach it to a piece of aluminum angle to help dissipate the heat and keep it away from the cells. The cells are connected through some magnets. I'm sure an actual 18650 holder would work better, but as I wrote, lack of preparation, etc.

So, it's not going to win any beauty pageants, but it works. I'll probably slap a voltmeter on somewhere so I know when the 18650's are tapped, but I have to find one first. I'm sure the $5 unit in Dom post is better in a dozen ways, but this was fun to make and satisfying to see working, so I'm happy.

 

[SnowplowTortoise]

Re: 18650 Cell Phone Charger - New Circuit Design

I'm back on the LM22671 approach. I'm hoping I can get rid of the heatsink and improve efficiency. But this is going to pull me in way over my head now. Here's the circuit I got from Webench.



The bill of materials amounts to about $4, so I guess there's no harm in trying. I apologize in advance for all of the dumb questions I will probably ask as I try to put this together.

 

[dom]

Re: 18650 Cell Phone Charger - New Circuit Design

I like the way this thread is going SnowPT.
Hopefully some electronic smarty will jump on the wagon Would be great to have a nice efficient charger.

A short update on my unit.
1. Still very happy with it
2. As expected it's pretty inefficient.
3 Does the job.

Have used it several times till the protected battery ran out (sorry battery).

Any future uses will be time limited to stop battery damage.(approx 5hrs -though will check this more thoroughly)

I was sick the other day so spent approx
5hrs reading ebooks on my phone -this is
where the charger comes in real handy.

My phone only had one bar left at the start of the day,and with all that reading
the phone was up to 2 bars at the end
of the charger life.

Cheers
Dom

 

[poormanq45]

his could be done with a pair of Li-Ions in series then use a buck regulator to drop down to 5v.

 

[sqchram]

Sanyo Eneloop Moblie Boost (the largest capacity model). 5000 mAh, Li-Ion, and they were at Costco being clearanced for $15!

Output is 500mah.

 

[Kremer]

Sanyo Eneloop Moblie Boost (the largest capacity model). 5000 mAh, Li-Ion, and they were at Costco being clearanced for $15!

Output is 500mah.

woa, awesome, get me one!

I think you mean 500ma output, no 'h'.

 

[sqchram]

woa, awesome, get me one!

I think you mean 500ma output, no 'h'.

right, of course, 5V 500 ma output, so suitable for most cellphones.

 

[Rod911]

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

I got mine delivered today. Bought from DX.

It's able to charge my N95 8Gb mobile just fine using the included 2200mAh unprotected cell. Also, most DX protected cells do not fit on this thing. However, the blue 2500mAh TrustFire and black/red 2400mAh TrustFire cells fit ok in it.

 

[spencer]

I would suggest taking a look at the mintyboost. If you can solder then buying the kit might be the easiest DIY method. The mintyboost is designed to work from 2XAA Alky I believe so 3V. The site says that you can use a lithium ion battery. If you wish to use more than one battery then you can just put them in parallel. Check it out.

 

[SnowplowTortoise]

Thanks Spencer - that's a great lead. I was just about to order the parts for my circuit, but the minty kit will actually end up being cheaper, and it benefits from being designed by someone who knows what the hell they are doing.

One question - do you think efficiency continues to improve as the input voltage approaches 5V, or is it really optimized for 3V as he writes? I couldn't tell from the graphs.