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HTC Charger Pinout

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By mschmiedel, Senior Member on 22nd August 2008, 04:43 PM
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As far as I've seen, the HTC Wall charger uses some other pin(s) to provide power than just the +5V pin of the USB cable; that's what makes it charge much quicker than a normal USB cable.

I'm interested in building a regulated charger for my HTC phone which will work with AA batteries (I'm thinking of using 4 batteries to get good power). However, I want to build a charger that works like the AC charger, that means, one that will charge the phone as fast as the OEM wall charger.

Does anyone have some specs on how these OEM chargers work? I don't think it's the USB port current limiting factor as I've tried with other USB power adapters (for car and AC) with 1A current specs, but they don't charge any faster than the USB port.

If I could get these specs, I will be able to post a simple enough and cheap design to get a reliable charger that guarantees stable current/voltage to the phone.
23rd August 2008, 12:22 AM |#2  
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It's worth reminding that Lithium Ion batteries need special charge management to ensure the battery is neither overcharged OR over discharged - and that circuitry is inbuilt to the PDA/Phone/whatever.
There will also be internal protection (some very complex - in computer batteries for example) - which is just as well because abused or damaged LiIon batteries can explode or go on fire.....somewhat rapidly.
Very different from NiCd or NiMh charging!

If you are to build your own charger or external supply (4 AA cells via a regulator?) I'd warn against anything other than the standard 5Volts.
The phone/whatever - itself - will take no more current than its charge management circuitry decides (even if you could provide 10 Amps) - and USB ports are generally limited to 500mA.

Here's an oddity...
I have an O2 charger believed suitable for an O2 XDA Orbit (HTC3300). The label on the side is "Strax (E11) 10R-02 4018". It's maybe lucky the cable termination was faulty and when I broke the connector apart to examine, I found not just the outer 5V and -Ve but also their neighbouring contacts factory soldered together i.e. 1&2 to 5V and 4&5 to Gnd.
Very puzzling because that puts -Data to 5V and ID/Key to Gnd!

Can anyone cast some light on this please?
23rd August 2008, 12:43 PM |#3  
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Hope this helps.
25th August 2008, 01:48 PM |#4  
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I recall from some other forums that some folks are charging their devices with a 9v battery feeding thru a 5v regulator IC, then on to a USB connector.

I've also seen a commercial cell phone charger in O'reilly's Auto Parts that uses a couple of AA lithium batteries with a dongle that has various USB connectors coming out of it.

Anyone here have any words of wisdom about doing that with a Tilt?
28th August 2008, 12:11 AM |#5  
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Those multi USB adapters are certainly a "must have" accessory for many devices.
Lithium batteries have very high capacity - unlike alkaline PP3 9V batteries.
A 9V Duracell / Mallory 1604 for example has far less capacity (around 500mAh) than a cellphone or PDA battery.

The 9V charger I have seems pretty typical and came as a kit in a nice zipper case with a selection of adapters.
Its circuit is much the same as others I've seen (at ridiculous prices for what they are)......as simple as one 5.1V 1 Watt Zener diode (1N4733A) in series with the battery and the datasheet quotes 178mA maximum regulated current. If that Zener should fail, pray it goes open circuit!

What this boils down to is such chargers are more for "get you going" emergency charge and at probably half the rate of your usual charger.
You'd exhaust at least two 9V Alkaline batteries to eventually recharge your PDA battery.

The O'Reilly charger with dongle (if 5V regulated) seems a better prospect but Lithium batteries are much more expensive than Alkaline. Something using a battery of AA cells and IC regulator makes better sense if a car charger, wall wart or computer's USB socket can't be used where needed.
28th August 2008, 06:52 AM |#6  
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Yeah, the appeal of being able to recharge (even partially) from AA or 9V batteries is that they can be obtained anywhere. Certainly not the cheapest charging solution though.
28th August 2008, 06:52 PM |#7  
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Yup! :)
When you give some thought to the many and different kinds of batteries we need to use there's a small fortune draining away (around my house at least). The battery market is Gigantic!

Looked at the price of Lithium batteries lately? (the non rechargeable sort) and how much does a 9V Duracell cost Stateside? In the U.K., one in a bubble pack is likely to cost £3.99 (over $7) and other makes are not all that much cheaper. Zinc Carbon types like Panasonic "Special" are half to quarter that price but they're low capacity, low current batteries. Your experience will vary among others with strange names and claims from far away factories (that can "take a leak" in the toxic sense :)

Rechargeable 9V batteries are maybe 250mAh capacity, aren't cheap, need their own charger and can take over 12 hours to charge.
Also, it's difficult to know how charged up rechargeable cells and batteries are when most needed. Their typical discharge characteristics are - now you see it...now you don't!

So unless there's great emergency (and the emergency charger + battery is available when it happens?) charging by wall wart or car adapter -for pennies- is the way to go for me :)
10th December 2008, 04:41 PM |#8  
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I use that, with the end removed and soldered on a female USB end, connected a standard USB cable and use that to charge my usb devices..
2nd December 2009, 05:14 AM |#9  
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Pin 1 is +5V. If I remember correctly, in order to quick-charge you must short pin 4 (normally NC) to GND, which is pin 5.. When the phone sees GND on pin 4, it knows that a charger is connected and shouldn't say "USB Connected". I've modded cheap ExtUSB headset cables to have charging capability, so I know this works.

NOTE: Do not attempt to use this on a computer USB port. The USB spec only allows a max of 500ma current draw, and pulling more than the port can output will possibly b0rk your USB port(s) and/or host controller!! Wall-transformers and car cigarette-lighter adapters are OK though..

Hope this helps!

-W5i2
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