No power after battery replacement

@mrtubbo "didnt try to charge it until a few days later and I replaced the battery. Now the screen wont turn on" enough time to have the corrosion process start and possibly create more short circuits. As you probably found out already, rice is not a solution. Check on here for more info on that. It is the equivalent of doing nothing, the only thing that happens is that corrosion will continue. So I'd be not using that anymore.

From here on you can only give it a try by treating it just like any other water damaged device. Start off by turning it off, do not try to turn it on, to charge or to sync it. This could potentially make a bad situation worse since it could shorten more components on the logic board out. Disassemble your phone by using this guide. Clean your phone with 90%+ (or better) isopropyl alcohol. Use this guide to clean your phone. It was written for an iPhone 3G but all the steps are pertinent to your phone as well. Inspect your board for any missing or damaged components. You must remove all the EMI shields to clean the board. Once properly cleaned, replace the battery and Lightning connector, then reassemble and re-evaluate. since you already changed the battery, you want to change it again and check the battery connector and the small components around it. Make sure that they are all still present. It is possible that you only have a damaged dispaly assembly but at this point anything will only be a guess. Water damage is the hardest to diagnose and to repair since almost any part can have failed.