I bought this device as a substitute for a 2100mA charger, which is unfortunately broken. Now I realized at a longer ride Tablet operating that this "3100mA" charger not even deliver enough power to operate an Acer TAB10 A3-A20, let alone still charging the battery pack! Despite the use of the original Acer USB cable so the battery was empty and had to be recharged only at a snail's pace before the tablet could be reused. Measurements using a smart phone which can display the current have shown that only about 750-800mA come - so much less than promised. The integrated USB port in the car creates even 500mA - with the difference then I need not use a separate charger.
Moreover, it easily slips out of the socket, you have after each movement of the tablet, check that the LED is still on.
