Review on Waterproof Motorcycle Dual USB Charger Kit by MOTOPOWER - Charge Phones, Tablets, and GPS on the Go with SAE to USB Adapter Cable by Onsommoshit Mathews

I bought these because the comments here said the battery drain was negligible. IS NOT IT. WARNING. It draws a small amount of power just because it's there - no USB device plugged in. No problem for daily driving. I took a week off because of the weather and the bike wouldn't start. The battery was barely enough to turn on the headlights. Instead of a planned trip, I had to recharge the battery that evening. So now I have to open the seat cover to connect or disconnect the battery. I'm not giving it any stars, but it's worth considering. It's true to convert 12V to 5V - there is a resistor that draws a small amount of current. When the engine is running, the alternator compensates for this loss. Be careful when the engine is off and parked. How long before you have problems if you leave this connected to your battery depends on the size of your battery. Otherwise works as advertised, has plenty of cord and a solid rubber cover. I will buy another one that comes with a (built in) circuit breaker for my bike and take that off.