She dropped it in the toilet and it was fully submerged. I took out the sim card and battery and blow dryed it. the next day i tried to use it and it wouldn't work. about a week later i tried again and now it works perfectly when it is plugged in but when i take it off the charger it only works for 5 minutes even though it says the battery is fully charged. does it just need a new battery or is it not worth it?