I am traveling to Spain in a short while and am trying to figure out how to most efficiently charge batteries and other electronics that have an american plug. I am curious to know if it's possible to get a power strip that will convert from 240 to 110v and then replace the plug with a plug for european use? What's the best way to go about this?

 

Many wallwarts are able to to use the 240V/50Hz you just need the plug adaptor.

 

Many won't. Do you want to just charge AA batteries? Buy a charger in Europe.

 

Everyone one of my chargers do except the cheap one I got surplus a couple years back.
It is a standard circuit.

 

You know, after re-reading the OP I see he wants a 240 to 110 converter. So he needs to know what power level (or current) will be required by the most hungry electric device he will carry with him. Then he can purchase retail the transformer/converter required.

If he's just carrying a laptop or other sophisticated device then I agree that his power adapter may work internationally.
If he wants to use a table radio, cheap shaver, etc. their adapters may be 110vac only. He has to know which is the case. He can't just use a plug adapter and find out
I thought/think it best to tell him.