Charging an iPhone using a Palm Touchstone

[Ricyteach]

This is my first post ever. I have arrived here at these forums because I have a fantastic idea, but I am only a civil engineer, which means I know jack about building electronics. So I need help. I've searched the forum for something similar but didn't find anything.

I plan to take the "guts" out of the back of a Palm Pre, which consists of an inductive-charging coil and circuit board:

http://www.amazon.com/Palm-Pre-Touchsto ... B002UNKGMC

attach it (along with the magnets, for securing the phone to the charger) to the underside of an iPhone case, such as a rubber Otterbox, and charge my iPhone wirelessly on a Palm Touchstone!

http://www.amazon.com/Palm-Touchstone-C ... cps_text_b

Something similar has been done with an Evo 4G here:

http://www.goodandevo.net/2010/06/how-t ... arger.html

However, as I have learned by reading the MintyBoost project pages, the iPhone has a much more complicated charging schema than the Evo, so I feel a little bit daunted here.

Here is what I know: when charging, the Palm inductive-charging coil delivers about 5V @ 1A across two leads that connect directly to the phone battery (though it may be 5.45V- I need to get out my multimeter and make sure). Since the inductive charger delivers 1A, I am assuming that it will be able to charge an iPhone in the "quick charge" mode at 1A instead of the slower 500mA.

Now we come to the part that I have no idea how to do: I need to take the 5V, 1A delivered by the inductive charging coil and convert it to the three 5V, 2V, and 2.8V lines required by the iPhone USB charger. This is something I am at a loss as to how to do! I have been trying to read up on it, but I am very confused. I wonder if someone could give me some direction? Remember that I have had university physics- which means I have a vague idea of how electricity works, and I am aware of Ohm's law and all of that, but I don't really know a diode from a capacitor. I would like to know how it works, but more importantly is to just know what components I need to buy and how to put them together. I will learn as I build.

Thanks in advance for any help.

[spikebrain]

Hey
I have the same idea. I have a touchstone dock and the palm pre back and have been experimenting...
What is interesting is that the palm usb power adapter thing doesn't put out any current on the usb data pins, but the iphone will still charge from the usb port using the iphone cable. I spliced an iphone cable apart to be able to experiment, here is what I found:

The iphone won't charge if you only connect the usb voltage pins, but it will if you short the data pins.
The touchstone dock won't charge my iphone through the sliced apple cable with the usb voltage pins attached to it and the data pins being shorted. (this surprised me and makes me think my touchstone might not be working correctly)

Anyone else have any ideas? I'd love to get this to work. I even found a place inside the iphone 4 where the palm pre inductive charging circuit board would fit.

[troop231]

I'm also trying to do this, however, I cannot by any means get the iPhone to stay charging once I connect it to the touchstone. I tried the 49K + 75K ohm resistors which didn't work, and I ordered about a dozen more various resistors which also did not work. I'm really stumped on what's wrong, because if I connect a cheap flip phone, it starts to charge at 500ma which the iPhone can do also.

I'm using the Palm pre back currently, but I saw on the internet where a guy had success getting his iPhone to charge using the Palm Pixi back; I thought these phones had the same battery capacity (1150mah) so I would assume that the charging circuits in the back are the same also, but just in case I ordered the Pixi back to see if that would work. It seems to be an issue either related to the data line voltages (I also tried shorting them together which I heard may work, but it didn't) or a voltage dropout because the power source can't provide enough current.

If anyone can offer any help it's much appreciated!

[pocketnavigation.de]

Hi,

I am also try to charge an iphone 3G with the touchstone system and does a lot of testing. It works when you put the inductive system directly on the touchstone (without a cover between the copper and the touchstone). But with the iphone cover between it do not work, it seams that the 500mA will not be delivered from the system. This is a little bit strange, because if you test it (with cover) with a multimeter you can drop nearly 500mA out of it, but the iphone will not charge. It is not the problem of the data pins (the can be shorten) because if you give him 500mAh through the same cable,it works. The problem is the thick iphone cover. I test only with the Pre Cover, but I guess the Pixi is the same! I only see three ways:

1) Thin down the cover
2) Load the Lipo directly
3) Find a way to force the iphone to charge with less then 500 mA

Problem 1) lot of work, not sure that you get it thin enough or too thin and it breaks
Problem 2) I do some tests with the batterie. There are four pins on the batterie. Is the loading system on the mainboard or is it near the batterie? I tryed to charge the batterie with a lipo charger outside the iphone and this does not work. Mayby we need a little charge eletronic and than charge the cell directly avoiding the lipo security eletronic. Does anybody have doing tests with this lipo and has a pinout for the four pins?

Do get the power from the pre cover i opend the dock connector from the back and fit a little cable to the pin 23 (extremly tight and difficut but it works). There is enought space in the 3G for all the inductive thinks, a little loading eletronic will also have space behind the dock connector.

I would by happy if we can find a way together. Mayby one of us can test it the way 1) and another the 2) way?

Best R.
Tobias

See it for Nexus S: http://www.pocketnavigation.de/2012/04/ ... g-nexus-s/

[pocketnavigation.de]

I tryed the first option: 1) Thin down the cover
It does not work, I drag it down more then 1,5mm and the cover was so thin that the light go througt it - but it does not work. The touchstone system does not deliver stable 500mA and so the iphone will not charge.

Now I have to work for the option 2) Load the Lipo directly

Best R.
Tobias

[Darebear]

Hello,

Are you guys sure the batteries are LiPo's? My understanding was that most consumer electronic batteries of the Lithium Ion flavor, specially for "low" amperage electronics.

The reason I say this is because LiPo's have a specific chemistry that may require a charging type very different from that of Lithium Ion batteries.