Iphone 4s running hot

Hi I have an Iphone 4s running hot, I have followed the process's on here (backup and restore) and starting a fresh on the phone and still have the same issue.

I have taken it to a local mobile phone dealer who has changed my battery and it still has the same issue, my battery is running hot like an application is constantly running.

I am now booked into the Apple store next week Monday.

I wanted to know, will this invalidate my warranty if I tell them I have changed the battery as I assumed it was a battery issue. It was changed by an approved phone dealership who is an accredited company for Nokia and Samsung and also do Iphone repairs/replacement.

I don't want to walk in there and them assuming the battery has been changed so they wont touch the phone now and say it is my fault.

Thanks