• After 15+ years, we've made a big change: Android Forums is now Early Bird Club. Learn more here.

Charging: USB and AC differences

hgmichna said:
Something else must be in the original HTC cable, and I hope to be able to measure it soon. Strange that nobody else has measured it yet, although the question has been open for quite a while.
Click to expand...
What doesn't help with that theory is:
1. I've not found a HTC cable long enough to reach around the dashboard to my cradle (longest I've seen is 1.2M)
2. the HTC cables are very poorly made, I've always bought Blackberry USB cables as replacements. Will let you know how I get on with the bodge on my cable.

Incidentally I'm using a Belkin F8Z445 (original in blister, not the 'ea' aftermarket OEM version, which might not even be genuine Belkin, it is built to slightly different specs and doesn't fit my 12V socket).

I recently bought a 1.2A/2A dual output adapter via eBay and it is a very solid unit indeed. I'm intending to use instead of the Belkin, as I've also got a Bluetooth visor hands free device to power, thankfully that only needs 500mA supply to charge, but still it's another metre of cable I need!
 
I've got the 1A Maplin adapter and have it apart ready for soldering the middle pins together. A little OT, but does anyone know of a way to re-route the LED so that it comes on when the USB cable is plugged in and not just when it's plugged into the car?

Maplin do a 2.1A one as well I noticed when I was in there, anyone know if that will work without modifying?
 
Could I, for instance, put the LED across pins 1 and 4 so that when the connector goes in in completes the circuit for the LED... No, that won't work as the LED will light as those are the power pins and will be 'live' already... How about the 5V+ pin and the shorted pins 2 and 3? But then where's the ground? I'm making this up as I type as you may have noticed :)
 
Si600 said:
... Maplin do a 2.1A one as well I noticed when I was in there, anyone know if that will work without modifying?
Click to expand...

Solid guess is no, because 2.1A is for the iPad which doesn't need this HTC modification ;)
The Apple modification is at the iPad cable (in the plug at iPad end of the cable, not in the USB plug).

Harry
 
Si600 said:
Could I, for instance, put the LED across pins 1 and 4 so that when the connector goes in in completes the circuit for the LED... No, that won't work as the LED will light as those are the power pins and will be 'live' already... How about the 5V+ pin and the shorted pins 2 and 3? But then where's the ground? I'm making this up as I type as you may have noticed :)
Click to expand...

I will not say "no way with simple rewiring" because you will it try anyway ;) :)

Harry
 
It took a while, but now I have a micro USB socket with 5 wires soldered to the microscopically small connectors.

To recapitulate, I had measured a whole range of different car chargers with two different charging cables, one from HTC, which came with the original HTC charger and is curled, and one that I made myself by cutting open the cable and shorting the two data lines, as described in: How to make a car charging cable for HTC smartphones | Windows Problem Solver

The result was that all combinations of chargers and cables led to a "Charging (AC)" indication in my Google Nexus One phone. However, with active Google Navigation, the original HTC cable led to a rising battery charge while navigating, while my self-made cable led to a slowly sinking battery charge. This happened consistently with all chargers, HTC or other, in several experiments. This means that the difference must be in the cable.

Measuring the cables, between the data lines I find 0.3 Ohm in the HTC cable and 2.6 Ohm in mine. Apparently the HTC cable's data line shortcut is in or very near the plug, while in mine it is half way down the cable, which explains the difference.

Since the resistance is very low in both cases and way below the prescribed limit of 200 Ohm, I am sure that this cannot explain the difference in behavior.

The extra contact in the micro USB cable, between ground and the two data lines, which I thought could be the culprit, is not connected to anything, neither in the HTC cable nor in mine, so this is also out of the question.

Since the data lines in my self-made cable go through to the USB A plug, while the ones in the HTC cable may not, I also measured whether there is any measurable resistance between the data lines and the power lines when a charger is connected, but I always measured infinite resistance. So this also seems to be out of the question.

In other words, these cables are essentially not different.

I cannot easily explain the results of my measurements. The cables are no different, the chargers all behave equally.

One highly unlikely explanation I can come up with is that the phone arbitrarily pulls a little more or a little less current, and I was extremely unlucky that this coincided with my cable changes.

Another equally unlikely explanation is that there is something in the HTC cable that I cannot measure, but the phone still detects. I have no clue what that could be.

What else could I measure? Any ideas, anyone? I would never have thought that this would happen. I was sure I would discover a clearly measurable electric difference between the cables. Alas, reality is always good for a surprise.

I will repeat my experiments with charging my phone while navigating a few more times, but I expect nothing new now.

If you have seen the same phenomenon, namely the phone showing "Charging (AC)", yet the battery level going down, please report here.

All ideas are welcome.
 
New member, here. I'm thankful I came across this thread! I just got a Galaxy Nexus and was having problems getting my (supposedly) Dual 1A Griffin PowerJolt to be recognized as an AC charge source. I shorted the pins as described and it worked!

I then proceeded to do the Palm Touchstone Inductive charge mod. Works great then touchstone is plugged into my Wall charger that came with the nexus so I know the cable works and the touchstone works. I could not however get it to charge on the 12V car charger modded to show itself as an AC charge source. I opened it up again and measured resistance between data pins and power/gnd. On the 12V charger there was a few kOhms between data and power pins so the data lines are being pulled to 2.5V. On my wall charger the data to power is open. So I found the 4 resistors on the 12V charger pulling the pins to 2.5V and verified they were now floating (open to pwr/gnd) and the 12V charger now powers the touchstone. I have not been able to verify if this will yield a faster charge on the phone directly connected but I thought I'd share because it did make a difference not having the data pins tied to pwr/gnd (despite being shorted to each other)

Cheers
 
The car charger might had a mod for Apples devices :D

To charge them rapidly with high current the data pins have resistors to power and to ground. With different proportions of the resistors for each of the data pins, the data pins will pulled to different potentials, which is the indication for Apple devices that they can charge rapidly with high current.

Harry
 
hgmichna said:
In other words, these cables are essentially not different.

I cannot easily explain the results of my measurements.

...

Another equally unlikely explanation is that there is something in the HTC cable that I cannot measure, but the phone still detects. I have no clue what that could be.

What else could I measure? Any ideas, anyone?

...

All ideas are welcome.
Click to expand...

Hi hgmichna,

Regarding your investigation into different cables influencing the charging rate, it may be that the power wires in the different cables have different resistances. If the HTC cable has only two wires then they can be thicker than those of normal USB data cables (for a given cable size), and hence have lower resistance (someone hinted at this earlier in the thread).

For HTC to go to the bother of making a special cable with shorted pins they must have had a reason to do so. It would have been cheaper for them to use a standard cable (since the PSU will probably already have the shorted pins).

USB charging uses only 5 volts so the voltage drop due to excess resistance in the power wires matters more than if it were say 12 or 19 volts. At 1 amp even a few tenths of an ohm will drop a few tenths of a volt. This may be significant, particularly if the phone uses a series regulator (as opposed to a DC to DC converter which could be more tolerant of a low input voltage) and the fully charged battery voltage is around 4.2V (as my HTC Desire S).

You can't reliably measure the resistance of the power wires directly using a multimeter. Instead you need to plug one end into an AC charger, put a load resistor of around 5 ohms (and 5 watts or more) across the power pins of the other end (e.g. using a spare micro USB socket) and measure the voltage across the resistor.

You may find that your cable drops more voltage than the HTC cable.

You could try making a cable with just two thick power wires, plus the "AC charge" short at the device end. Mark it "Not for use with computers" or similar.

I hope that helps. I've not tested it. Thanks for your detailed investigation. I need a solution to the problem myself.

JB.

(First post. I appreciate that this thread is a few months old. However I don't think the issue was resolved).
 
Thanks for your response! You are right. I just tried to measure the resistance of my cables, and it is, indeed, too high. I measure about 2 Ohm along one wire, i.e. about 4 Ohm altogether, which makes me wonder how it could ever charge the phone at all.

I will look for better cables. Too bad that cables with data shortcut don't seem to be available, so the available data cables still have to be converted with tedious manual work.

Another problem is that the manufacturers generally don't hand over complete technical data, so the only way to find out is to order a cable, measure it, and return it, if it is bad.
 
Most microUSB cables have 28AWG wires for data and power.

My HTC microUSB cable has 28AWG/26AWG for data/power.

DeLock has micoUSB cables with 28AWG/24AWG for data/power.
DeLock shows that specs on its product sites.

Thicker wires for power I only found with USB A cables.

The resistances for the wire gauges are shown here ... :)
http://diyaudioprojects.com/Technical/American-Wire-Gauge/

Harry
 
Hi there,

I have been noticing stuff like some of you.
Cables are very important and the HTC one give me good result when new. My phone usb female connector being weak it does not connect very well when the male usb is a bit worn (less insertion force).
So far my best charging cables are some "retractable" charging cable. The connector enclosure is pretty weak. I have been opening some (they are in two parts, not molded), put some glue in and close back. As it is a charging cable, there is only two wires, therefore there is not much to do on the charger side.
On the micro usb side, there is a 200kOhms resitor between the blue wire (which I guess is the ground but I did not verify yet) and another point. The problem is to be sure to what pin it is linked is a bit complicating without using a broken cable...
I can take a pic if you are interested, anyway I guess the resitance is connected to the fourth pin ID (the one thta does not exist on regular usb).
I am moving house at the moment, and my iron is already moved. Anyway I hope to be able to more experiment this month.
Identify to what pin is connected this 200k Resistor.
Try a resitor bridge to provide 2V to D+ and 2.8V to D- (for my normal cables).
Try to shunt charger side D+ and D- (for my normal cables).
Find more charging cables that are easy to mod (ir not molded connectors). I cant find my weak cables anymore!
Then when I have a conclusion, modify all my charger and or all my cables.
 
OK I have been checking, there is a 200K resistor between pin 4 and 5, I will modify my cables this way, using this if needed (to replace molded connector):
eBay - New & used electronics, cars, apparel, collectibles, sporting goods & more at low prices

I have found various tutorials that say more or less the same except about the resistor value 619k and 301k. I highly doubt on the 1% stuff! I would recommend 400k +-50%!

[DIY] "Car Dock" Cable - USB audio out + charging - UPDATED! (11-9-11) - xda-developers
Samsung Omnia 7 or galaxy S JIG
 
I have the CC C200.
It charges the One X properly while using power consuming navi apps, but it doesn't put the phone in car mode.

The cable of the CC C200 is a coiled cable, I think more than 1m long.
If you want to know the exact length I'll measure it in the car tomorrow.

Harry
 
I just converted a Kodak USB AC adapter rated at 5v 1amp. It was only showing USB charging. Pins 2 and 3 showed opened. The adapter was disassembled and a small surface mount resistor was soldered between pins 2 and 3. The HTC Desire phone now shows AC charging. The adapter is rated for 1 amp and all of the components and PC board looked like it could handle 1 amp continues and maybe a bit more depending on the drive transistor and wires in the transformer and running frequency. I am using the HTC USB cable. I am pleased that I now have a fast charger for work when the phone decides to drain the battery every once in a whille. I plan on going through all of my USB chargers and seeing what's what on them.
 
I know that this thread has been going for a long time and am wondering if you can now buy a car charger that works out of the box other than a genuine HTC car charger?

Can anyone recommend one that they know works well even when using satnav on the phone?

Thanks
 
Why not buy the original HTC charger, like this one: Genuine HTC CC C200 Micro USB Car Charger: Amazon.co.uk: Electronics (no guarantee—there are some fakes on the market).

Or buy this adapter, which makes all good chargers workable:
http://www.amazon.co.uk/dp/B004IFQZ9S

In fact, I have bought this from the German site:
http://www.amazon.de/gp/product/B004IKTYXM

I can attest that it solves the problem. I suppose this is the same one as that on the Amazon UK site, but cannot be sure.

What you can do is buy a charger first and test it. If it gives you only "Charging (USB)" then buy the adapter.
 
Spytek said:
I know that this thread has been going for a long time and am wondering if you can now buy a car charger that works out of the box other than a genuine HTC car charger?

Can anyone recommend one that they know works well even when using satnav on the phone?
Click to expand...

I bought and have used a couple of other chargers from Amazon UK - you can see my reviews of each charger here:

Amazon.co.uk: dj.si's review of Prepaymania In Car Micro USB Charger for H...

Amazon.co.uk: dj.si's review of totaldigitalstores - In-Car Windscreen Suc...

Both chargers provided adequate current out-of-the-box to increase the charge in the battery of my HTC Desire even while using the Google Navigation app constantly.

But some points to bear in mind:

- Both chargers have a curly cable with a micro-USB plug on the end, i.e. neither is a universal charger with a standard USB socket - these chargers can be used only for devices which have a micro-USB socket.

- Once the phone is charging with any charger, find the battery information (somewhere in the phone's Settings) and check whether it says "Charging USB" or "Charging AC". If it says "Charging USB" then it won't be enough to stop the battery gradually draining while using Google Navigation. And if the charger was advertised as a high output/1 Amp charger then you're legally entitled to send it back for a refund (including any postage costs) because it's not doing what it claims to do, i.e. it's been mis-sold/mis-represented.

- Buying from Amazon Marketplace means you're covered by Amazon's Marketplace guarantee ...but always read the smallprint! ;)

HTH!
Si
 
dj_si said:
I bought and have used a couple of other chargers from Amazon UK - you can see my reviews of each charger here:

Amazon.co.uk: dj.si's review of Prepaymania In Car Micro USB Charger for H...

Amazon.co.uk: dj.si's review of totaldigitalstores - In-Car Windscreen Suc...

Both chargers provided adequate current out-of-the-box to increase the charge in the battery of my HTC Desire even while using the Google Navigation app constantly.

But some points to bear in mind:


- Once the phone is charging with any charger, find the battery information (somewhere in the phone's Settings) and check whether it says "Charging USB" or "Charging AC". If it says "Charging USB" then it won't be enough to stop the battery gradually draining while using Google Navigation. And if the charger was advertised as a high output/1 Amp charger then you're legally entitled to send it back for a refund (including any postage costs) because it's not doing what it claims to do, i.e. it's been mis-sold/mis-represented.
Click to expand...

Do both of these show as "charging AC" when plugged into the car cigarette lighter? Thanks
 
Yes, as mentioned, "Both chargers provided adequate current out-of-the-box to increase the charge in the battery of my HTC Desire even while using the Google Navigation app constantly" - this is true only for "Charging AC" chargers, i.e. the ones that really do provide a high output, as opposed to the ones which are advertised (mis-represented) as high output but in reality only provide low output (the same low output as any computer's USB sockets).

If you're in any doubt, it's worth e-mailing the seller and asking for confirmation that a specific charger will definitely provide high output/adequate output to increase the battery's charge while using the phone's sat nav. Then their reply will be written confirmation, so if it then turns out after you've bought the charger that it's actually not providing high output, they can't argue and must give you refund, including their postage costs for sending it to you AND your postage costs for sending it back, because it was their mistake in selling you something that doesn't do what they said it would do. Though many retailers/online sellers try to wriggle out of their legal obligations, that's UK consumer sales law - it's there to protect us, the shoppers! ;)
 
You must log in or register to reply here.
Back
Top Bottom