I didn’t get my FP under 50% for now, so I cannot say that. It charged very quickly with both chargers.
It’s very hard to measure the charging current, because if you put a multimeter or any measuring device inside the line, the resistance of the cable is higher and the charging current will be lower… 
When I’m home again, I will try to get better measurements.[quote=“therob, post:31, topic:11668”]
Do you say, the FP2 charging electronic comunicates actively with the electronic of the charger?Can you provide a link for this as it is quite new to me? For PC-FP2-USB-connection sure. But between FP2 and charger??
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No. Sorry, English isn’t my first language. 
I did mean, that there is a “protocol” for the device to recognise the charger. So it gets the information about the charging current by checking the mentioned resistor and raising the current until the voltage drops a defined threshold.
This is the “Battery Charging Specification” (see here), but I don’t know, if the FP sticks to this specification.
As I mentioned, there are several different specifications (better word than “protocol” ;)) for charging, so the charger needs to recognise the device and stick to the specification the device complies to. There is more logic than just putting a resistor between the data lines to use the charger with more than one device.[quote=“therob, post:31, topic:11668”]
To my knowledge for charging you just need pin 1 and 5 to make use of the charger. Pin 2+3 are for data transfer only (PC etc.) and pin 4 only if you want to tell the client to provide power instead of consuming (e.g. for OTG)
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As you can see in the specification, the data lines are used to indicate the device that it may take energy from that port. The USB specification says, without any information the device is only allowed to consume 0,5 mA. I don’t know if all devices do that, but the FP2 obviously does, so you’ll always need a cable with all four lines (5 V, GND, D+, D-; ID is only for OTG).[quote=“therob, post:31, topic:11668”]
So for what exactly does it stands for?
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In contrast to Apple, most devices with Android comply to the named standard, as far as I know. (We didn’t get that information yet!)
Sorry, these measurements are not significant if you measured at the primary side. The phone doesn’t charge linear at all (read about li-ion charging!), also your assumption of 100% efficiency is very bad (70% are a lot better). In addition to that, most cheap power meters do not consider the power factor correctly 