maemo.org - Talk - View Single Post - charging Time on the N9

	ototo	2012-01-05 , 19:34
	Posts: 14 \| Thanked: 21 times \| Joined on Sep 2009 @ Helsinki, Finland	#14

Originally Posted by vip

Informative indeed.

However, it does not explain the following: if I use an iPad charger (5.1V, 2.1A) my N9 charges more slowly than with Nokia's own AC-16 (5.0V, 1.0A).

So there must be some sort of device identification/"compatibility" going on here. If that's the case, it is pretty annoying.

According to USB Battery Charging Specification v1.2, chapter 4.4.3:

A DCP shall have an impedance between D+ and D- of RDCP_DAT.

where RDCP_DAT is defined in Table 5-3 Resistances as 200 Ohm max.

I have no idea what happens if that impedance is higher than that. If it's very high (e.g. unconnected pins) - the "charger" will not get detected at all (tried with cheap car USB charger).

So, I'd suggest you to measure impedance between two middle pins for both of your "chargers".

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