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Different charging time depending on USB connection mode? [answered]

asked 2014-04-12 14:25:34 +0300

cquence gravatar image

updated 2014-04-12 14:28:54 +0300

Sometimes when I plug in the wall charger I get the option to select between PC Connection/Developer mode/Charging only as if I were connecting to the PC. This behavior doesn't happen all the time, most of the times it goes straight to USB charging without the prompt.

What I have noticed is that despite the fact that I selected the "Charging Only" option from the lockscreen, the device doesn't charge as fast as in the case when it goes straight away to "USB Charging".

Is this related to how the charger gets plugged in maybe? My current theory is that the phone/OS doesn't detect the 1.0A charger every time but sometimes it assumes that a 500mA (PC) connection is present (I don't know what is causing this, OS/way of plugging in/hardware circuitry??) and therefore it is presenting the options to choose from (PC/Dev/Charging). So then by selecting Charging, it still operates under the 500mA mode and this leads to the increased charging times.

Has anybody else also noticed this??

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The question has been closed for the following reason "the question is answered, an answer was accepted" by gabriel
close date 2014-04-13 13:26:58.886016

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Does this still happen if you first connect to the phone and then to the charger? It may be the speed at which the connection is made determines how the phone detects the charging current capacity of the charger. Richard

richardski ( 2014-04-12 17:33:37 +0300 )edit

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answered 2014-04-12 18:53:11 +0300

Philippe De Swert gravatar image

updated 2014-04-12 19:25:38 +0300

Yes sometimes when the cable gets inserted too slowly the detection is not completely correct. This is due to the actual design of USB so not much can be done about it. For charger detection the D+ and D- lines have to be shorted. And while inserting there is a short time where they are not actually connected correctly while VBUS and GND are already detected. Thus it gets wrongly detected. This is more visible because the Jolla has a relatively loose USB connector on top and tighter at the bottom.

So basically you are plugging it in wrong ;) If you play around with other devices you could reproduce this very easily by not completely plugging in the cable. You can get the same very easily on N9 too if you try hard enough. On other phones it happens too, it just gets hidden from the/is not visible to user on android for example due to the way they have notifications.

And as richardski points out, this will not happen when plugging in the charger to the phone before plugging it in the wall socket.

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Thank you very much for this detailed explanation!

cquence ( 2014-04-14 00:15:13 +0300 )edit

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Asked: 2014-04-12 14:25:34 +0300

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Last updated: Apr 12 '14