..... the cheaper ones cause interference on radio/television/WiFi.
We had an initially puzzling example of this recently with a dual USB output adapter cigarette lighter plug in automobile 1 (hers). The device was being used for the first time to power the sat-nav device. Our favorite FM radio station was 'weak' and overwhelmed most of the time by white noise. Eventually it dawned on me to remove the adapter. Result? noise gone, station returned to full quieting, and domestic peace returned.
I endorse everything else offered above about charger ratings etc. The usb concept is finding it's way into all kinds of applications - my micro model glider needs a USB outlet to charge its micro sized battery.
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