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

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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

JJames

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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JJames

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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JSJon 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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JSJon 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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MMSK

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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JJimbo

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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