I bought an iphone 4s on ebay last year used. Condition of it was very good condition. The seller had used the iphone for 3 years i believe but condition when received was great. Battery was very good as well. Not long ago I noticed the battery of the iphone 4s seem to be a lot less than normal. First off, is there a way to confirm this? I check online and read if you go to diagnostics, you would find low battery low in the data. So that would be true? How much does replacing the battery for the iphone 4s would cost around? I know i cannot replace it myself as i cannot open an iphone.