Portable 2000mAh iPhone 3G Charger

[bsodmike]

I was able to slap this together in little under an hour. I probably spent the most time procrastinating whether to solder in a USB socket or not. Since I have run out of those in my lab, I decided to directly wire up an iPod cable.


If the photo does not load: http://twitpic.com/xdc8k

Specs:
-2000mAh Li-Pol pack, with around <8% per month discharge rate.
-Rechargeable via USB.
-Can power an iPhone/iPod at the same time.
-USB charging from PC -> device charging at 100 mA
-5-7VDC adaptor input -> device charges at 300 mA
-LED flashes when battery is charging; stops when fully charged.
-No on/off switch! (granted, there is quiescent current drain by the DC-DC booster...whatever )
-Works with all iPod/IPhones - even older models. They all use 5VDC input

I'm sure if I took the time to bridge both the Li-Pol charger circuitry and the 5VDC boost circuitry onto a single PCB, this could be made much smaller. As a prototype however, this is good enough Will post some better pics when time permits.

[digit]

Very impressive work Why did you decide to make it?

[samcross]

Nicely done Michael

How many hours charge will it give you?

[bsodmike]

Nicely done Michael

How many hours charge will it give you?

If you look at step 28 @ iFixit, you can see it is a similar type Li-Pol battery in the iPhone 3G; it too supplies 3.7VDC. It is however rated at around 1150 mAh, and is also mentioned here. It should not be a problem to charge the iPhone 3G completely from 0% to a full charge with my pack; will be doing a bit more testing in this department today.

Very impressive work Why did you decide to make it?

I have recently started to use my phone a *lot* more for 3G, tweeting and spending many constructive hours on faceache. For a while I have also been hunting for a decent iPhone car charger but it slipped my mind when I was in Singapore and none are to be found locally - when going to the estate, you'll usually find me moaning how my battery is about to die...no more

The danger my kit poses though, is that if there is a short, one can expect lots of smoke, fumes, and even a small fire. I am speaking from experience in the past, with regards to a bad experience with a high-power Airtronics battery gone wrong. It pretty much ignited in my hand and I just flung it on the granite floor where it just smouldered to a crisp. That said, everything inside the box is packed quite snug and there isn't much room for shorting.

I think I may have to look into attaching a USB receptacle, as the cable strain is not going to last long on the solder joints. The USB port can be glued into the case - similarly, I will be making a small opening on the other side to allow for the mini-USB port to connect to charge the internal battery thereby no longer needing to open the box again...ever!

[merdat]

Nice work there old thing.

[bsodmike]

Nice work there old thing.

Thanks

Here's a pic of it charging; right now I have to open the lid to do this. http://twitpic.com/xi9lg
The LED turns off once the battery is charged. One can also leave an iPhone connected simultaneously!

[Rave]

Nice! But if you're putting it in such a large box, you might as well use 3xNiMH AAs surely? Cheaper, higher capacity, more robust? More self discharge I suppose, but you could use Eneloop type batteries if that's a concern.

Did you design the charger circuitry yourself? If so any chance of a schematic?

[bsodmike]

Nice! But if you're putting it in such a large box, you might as well use 3xNiMH AAs surely? Cheaper, higher capacity, more robust? More self discharge I suppose, but you could use Eneloop type batteries if that's a concern.

Did you design the charger circuitry yourself? If so any chance of a schematic?

I had a couple of these boxes kicking about in the lab. The circuit uses a Maxim MAX1555 charger IC - it really does all the *magic*. You can find the schematic in the datasheet. I am using the charger made by SFE, something I bought a while back for a small robot.

The Sys/Gnd connection connects to a DC-DC boost circuit, that takes 3.7VDC and outputs 5VDC. In the first photograph of the box, you can see I've soldered on an electrolytic cap on its output to smooth and decouple it (~220uF). This was quite plug n' play with bits I had lying about; a really simple concept with the MAX1555.

Apple could rather easily integrate ALL this into one of their Docks. This way, the dock will act as a portable iPhone charger as well, as providing line-out to any HiFi sets. Some people have also attached Solar panel chargers into the 5V/Gnd port of this board...it is something I could do as well, if I get *desperate*.

[Mike Fishcake]

The danger my kit poses though, is that if there is a short, one can expect lots of smoke, fumes, and even a small fire.

So, normal Apple quality then?

*Disclaimer - happily using an ipod touch*

[Konan555]

The Sys/Gnd connection connects to a DC-DC boost circuit, that takes 3.7VDC and outputs 5VDC. In the first photograph of the box, you can see I've soldered on an electrolytic cap on its output to smooth and decouple it (~220uF). This was quite plug n' play with bits I had lying about; a really simple concept with the MAX1555.

Decoupling would be removing the DC component of a signal, would it not? Do these phones charge from an AC source? But then again, you said smoothing too?

[mikerr]

We lesser mortals have to buy a pre-made one

http://www.amazon.co.uk/exec/obidos/ASIN/B0017H4G0A

or a smaller one that sits on the back of the iPhone:

http://www.amazon.co.uk/exec/obidos/ASIN/B001XURLQM

[bsodmike]

Decoupling would be removing the DC component of a signal, would it not?

I think you're referring to the operation of a cap when wired in series with an input signal, i.e. capacitor coupling. In this way they do pass AC and block DC, however, that is not the purpose of a decoupling capacitor.

It is best described here, where,

High frequencies and transient currents flow through a capacitor, in this case in preference to the harder path through the decoupled circuit, but DC cannot go through the capacitor, so continues on to the decoupled circuit.

Therefore, you will typically see this attached in parallel across your supply source. Since the supply source in *this* case is my boost circuit, I decided to decouple its output. I would call this a 'force of habit' as I have been, largely, for the better portion of the past few years designing micro-controller circuitry; line noise can lead to some nasty issues. It's not a requirement in a simple charger though.

I guess it's one of those "thrown in for good measure" moments...

Do these phones charge from an AC source?

None that I know of. They all use some sort of DC based charger; the switch mode chargers being more efficient rather than classic transformer regulated supplies that tend to be huge power wasters.

But then again, you said smoothing too?

It does smooth out the supply as well, if there were to be any spikes or sudden dips.

[bsodmike]

We lesser mortals have to buy a pre-made one

http://www.amazon.co.uk/exec/obidos/ASIN/B0017H4G0A

or a smaller one that sits on the back of the iPhone:

http://www.amazon.co.uk/exec/obidos/ASIN/B001XURLQM

Both of those are retailing for 35-quid each! That's a nice profit margin I must say. I had my "baby" charging yesterday - it took absolutely ages to charge over USB; seem the MAX1555 limits the charge current to 100 mA and this would take eons considering that I'm using a 2 Ah Li-pol pack. The alternative would be to wireup 'another' USB receptacle and pass that supply into the boards 5V/Gnd port - this should allow it to draw its maximum 280 mA, and offer a modest improvement.

Decided to crash into bed and closed up the box, put the four screws into the lid and had it sit on my night stand whilst charging the iPhone. It charged 10% in about 10 mins, which was about right. The 3G reached its usual toasty self once fully charged. I'm chalking this one under 'success'

[watforddude]

Very Impressive

[Konan555]

I think you're referring to the operation of a cap when wired in series with an input signal, i.e. capacitor coupling. In this way they do pass AC and block DC, however, that is not the purpose of a decoupling capacitor.

Component is performing the same function, just different purpose to it being in serial. Since in parallel it is passing the AC down ground leaving a steady DC for the output.

Somewhere along the line, I've picked up the term 'decoupling capacitor' to mean, as I said before, to remove the DC component in signals between circuits. No idea why, but I shall attempt to get it out of my system.

[bsodmike]

Component is performing the same function, just different purpose to it being in serial. Since in parallel it is passing the AC down ground leaving a steady DC for the output.

Yup..