Can I use a max 250 volt adapter to charge a 5 volt device?

I'm going to Spain in a few weeks. I found a 250 volt adapter which is perfect for my iphone… But is it too strong for my 5 volt charging case? I don't want to burn it out. Sorry if this is a stupid question, I don't know much about electronics / engineering.

Check the input and output ratings of your charger. I bought an extra one ($7 at Walmart; it's just a little cube like the one that came with my phone, but the prongs fold into it making it more compact) for my iPhone. In can be plugged into 120V AC such as we have in the USA, and also 240V outlets (with suitable adapter) as is common in European countries and elsewhere. The adapter I speak of merely provides prongs to fit the foreign wall outlets. The input rating for my charger says something like 120VAC/240VAC 50Hz/60Hz. The output of the charger is a USB connector, which provides 5VDC.

Go check the charger you have now.

All the chargers I have seen in the last 20 years are universal 100v-250v input
(because they know people travel around the world - I know I do! And do not need to change mine or for the PC)

So I expect that the one you have now is perfectly OK already.

If you do need to change, ANY USB charger with upto 250 volts input will be fine.

Remember the thing is, Spain (and all of Europe) use small round pins…
maybe easier to buy a new one locally (will not cost much these days).
Otherwise,
you will need a pin adapter… From your normal sockets (flat pins) to Euro ones (round)

See the type you will see in Europe
(top picture - German CEE 7/4 plug and CEE 7/3 socket)
https://en.wikipedia.org/...nd_sockets

one of these will change the pins for you
http://www.amazon.com/...005HGZF7U/