The problem is that most 3rd party chargers have usb pins 2+3 connected through a resistive voltage divider to accommodate Apple products , other products such as HTC to date ignore USB pins 2+3 , Samsug prooducts look for a short between pins 2 and 3 , if you take a after market charger and measure resistance you will see approximately 30K ohms between pins 2+3 , The Samsung phone will charge at haf rate 0.2% per minute and the charge indicator will not work properly , taking this aftermarket charger (lighter plugs included) breaking them open and soldering a short between 2+3 will solve this issue completely , the Samsung uses the new convention of USB . Please read the Wikipedia excerpt below ...all of my modified adaptors work great and charge in half the time prior to this mod...If you're lazy simply slit open a USB cable and short pin 2 and 3 usually green and white wires . Hope this helps everyone .... Regards Howard Rosen VE2AED
Charging ports and accessory charging adapters
The Battery Charging Specification of 2007 defines new types of USB ports, e.g., charging ports.[43] As compared to standard downstream ports, where a portable device can only draw more than 100 mA current after digital negotiation with the host or hub, charging ports can supply currents above 0.5 A without digital negotiation. A charging port supplies up to 500 mA at 5 V, up to the rated current at 3.6 V or more, and drop its output voltage if the portable device attempts to draw more than the rated current. The charger port may shut down if the load is too high.
Charging ports exist in two flavors: charging downstream ports (CDP), supporting data transfers as well, and dedicated charging ports (DCP), without data support. A portable device can recognize the type of USB port from the way the D+ and D- pins are connected. For example, on a dedicated charging port, the D+ and D- pins are shorted. With charging downstream ports, current passing through the thin ground wire may interfere with high-speed data signals. Therefore, current draw may not exceed 900 mA during high-speed data transfer. A dedicated charge port may have a rated current between 0.5 and 1.5 A. There is no upper limit for the rated current of a charging downstream port, as long as the connector can handle the current (standard USB 2.0 A-connectors are rated at 1.5 A).
Before the battery charging specification was defined, there was no standardized way for the portable device to inquire how much current was available. For example, Apple's iPod and iPhone chargers indicate the available current by voltages on the D- and D+ lines. When D+ = D- = 2V, the device may pull up to 500 mA. When D+ = 2.0 V and D- = 2.8 V, the device may pull up to 1000 mA of current.[44]
Dedicated charging ports can be found on USB power adapters that convert utility power or another power source ? e.g., a car's electrical system ? to run attached devices and battery packs. On a host (such as a laptop computer) with both standard and charging USB ports, the charging ports should be labeled as such.[43]
To support simultaneous charge and sync, even if the communication port doesn't support charging a demanding device, so called accessory charging adapters are introduced, where a charging port and a communication port can be combined into a single port.
The Battery Charging Specification 1.2 of 2010 [9] makes clear, that there are safety limits to the rated current at 5 A coming from USB 2.0. On the other hand several changes are made and limits are increasing including allowing 1.5 A on charging ports for unconfigured devices, allowing high speed communication while having a current up to 1.5 A and allowing a maximum current of 5 A.