Iphone 4 battery life dropping dramatically?

I bought a iphone 4 of ebay in october last year. When the phone came it was faulty but i did know this as i the seller described that it was faulty. I bought a new speaker for the phone as it sounded distorted and you couldnt hear it when it was at full volume. The new speaker i fitted worked and i could hear the iphone with ot it sounding distorted. Since i put in the speaker the iphone has lost battery life during the day. When i'm at work it is at 50% by 1:00PM. I turn all the brightness down close all my apps Wi-Fi is always off. I don't understand why it is losing battery life so quickly all i did was replace the speaker.

You probably need a new battery but you invalidated your warrenty as an apple certified dealer did not mend it

I have noticed since the iphone 3 came out the newer iphone battery is not very nice. It says it is a really good battery but once you get its not. If you have not recently purchased it i would say go to an android.

Since you said seller then you don't know how they took care of it. My iphone battery, if it was at 100% in the morning, and I didn't us it, at 1PM it would still be 99 or 100%… If you want a comparison. You might want to just have a new battery put in. If you aren't under contract, I would just do a 2 year contract and get a new iphone 4 free.