I have an arduino esplora. Recently I bought a tft lcd for it. The thing didn't work but that is different problem. I am waiting on a new one but the thing uses my 5V and GND pins and to stay mobile I used a 5v battery pack. Now the pins are taken by the lcd, so I bought duracell mobile usb charger. It works for 3 seconds than the yellow LED L starts blinking. She does work when the battery is plugged in in the 230v but when i remove it it lasts 3 seconds. Is this solvable or is battery voltage to low??
Best guess at this point is that your exceeding the 500 mA limit for USB.
USB is still a black art, but I know Motorola uses pull ups on the data lines to set the maximum current.
There is a USB "Charge port" that acts a bit differently,
There are a few devices that I know of that can help measure the USB port: