can i use a 4.5 volt ac adapter on a device designed for 4.2 volts?

Answer 1

That should be no problem at all. But beware, make sure the "tip" polarity matches the device you're using it on or you could damage the device!

Tip polarity is shown as a small diagram on both the adapter and the device you're using it on. It should be right beside the adapter hole on your device and it should be shown on your adapter where it shows what voltage it is. It should show a dot within a circle and a line protruding through an opening in the circle. At the end of THAT LINE you will see a "+" or a "-". That is the tip polarity. If the symbol at the end of THAT LINE matches on both the AC adapter AND the device you're using it on you're good to go! If the symbols do not match DO NOT USE THAT ADAPTER!

Some adapters have detachable ends on them which can be turned around to make the polarity match. You can see the word "tip" on one end and "+" or "-" on the detachable end. Simply connect them so that the "tip" matches what is shown on your device.

I hope this was helpful. Good luck!

Answer 2

Yeah, especially if all it's going to do is charge a battery, as on a cell phone. The voltages aren't all that precise, and 4.5v is only, lessee, 4.5-4.2=0.3v, 0.3/4.2=seven percent over.