If its just the battery terminals corroded, open it up and remove the terminals/battery compartment if you can. Lightly file or sand with a really fine grit sand paper, the corroded terminals and wipe the rest off, with vinegar. Also, check the soldered connections to the wires that are attached to the terminals, as they might have been damaged.
Oh, and be careful when doing this as the stuff you are cleaning off is an acid and can cause injury. Make sure you do not touch it with open wounds and do not touch your eyes etc and thoroughly wash your hands after.
This guide should help you as well; http://www.wikihow.com/Clean-Battery-Corrosion-and-Build-Up
Hope it helps mate