7HTC Desire Android LogoFixed: HTC Desire charging slowly from car charger

I have an HTC Desire, which I frequently use as a Sat Nav system.  I have a car charger, but this is often barely able to keep pace with the power draw of the phone.  This seemed strange as the official HTC wall-wart charger that came with the phone can fully-charger the battery quite quickly.  I did some research and discovered that the HTC wall charger has the USB data pins (pins 2 and 3) shorted.  The phone detects this and increases the total power it draws whilst charging.

I believe that other phones may also use a similar system.  On the Desire it is possible to check which kind of charge mode the phone is using by going to Menu: Settings: About Phone: Battery.  The battery status can be displayed as either Charging (USB) or Charging (AC)

The fix to the slow charging issue, the usb data pins need to be shorted, either in the cable (not recommended if you want to use it as a data cable) or in the car charger itself.  I couldn’t see any downside to the latter so that is the route I took.  I should also point out at this point that I got a car charger which specified at least 1amp output.  Chargers specced for 2amp output are widely available now and I would recommend getting one.

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7 Comments

gravatarJames

Thanks for posting this. My car charger was showing “USB” and charging slowly even though it was supposed to be able to output 2.1amps. I followed your procedure and now it shows “AC” when plugged in. I’ll give it a try and see if it speeds up charging.

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gravatarJames

This definitely sped up the speed of my car charger. Thanks for the tip! I don’t know why they don’t just manufactuer them like this!

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gravatarJon Scaife

Official HTC chargers are manufactured like that. I agree though – all should be – you don’t need the data pins for a cigarette socket, so why not! Glad it worked out well.

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gravatarJon Scaife

Thank you for your comment. I have left your link in, even though it is shameless self-promotion. I don’t advise readers to follow the link however as the article you linked to doesn’t address the same issue. A broken cable obviously needs to be replaced and has nothing to do with a phone charging quickly from the wall and slowly elsewhere. This article highlights the fact that most smartphones have 2 charging modes – an “AC” mode and a “DC” mode (HTC explicitly call the 2 modes by these names and display which type is being used in their charging status). This article explains how to “trick” the phone into using AC mode even when it is not connected to an AC charger. The reason phones do this is so not to pull too much current from a standard USB as it may risk damaging it. This trick is only advised when you know that the source you are modifying is specified to provide the current required.

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gravatarMSK

I did this mod for my HTC Amaze using a 2amp IPAD car charger. the current going into the charger(12V) went from 250ma to 490ma and my phone displays AC instead of USB. Thanks!

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gravatarJimbo

Hi, I found some posts regarding an update to the android OS causing some chargers to act this way. This solution corrected the issue on my LG phone… thanks for an extremely helpful post.

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