If the resistance between the data pins is over 200 Ohms, the device will not detect the chanrger as a high current source and therefore limit the current to 100mA. That the current it is allowed to draw from a PC USB port without requesting more power. Since most wall chargers do not yet follow this new rule, they will only charge very slowly. This is the case with most wall chargers I tested. My solution was to use an USB extension cable and shorten the data wires. This doesn’t hurt at all, even you still would connect it to a computer.