Answer to "iMac won't boot after RAM upgrade"Ensure you have seated all RAM sticks properly in their slot, verified the keying matches and visually inspected the metal contacts between the RAM and the motherboard. There should no play in the installed RAM. This generally takes more force than is usually expected. Your system's symptom is typically that of no RAM installed. Check back with more information as it becomes available to you.
Answer to "Completely dead and unresponsive iPhone"Ben, I'm going to say its the charge controller on the board. If it ever overheated it could have damaged its circuitry and won't charge the battery properly or at all. A warm battery that didn't charge is indicative of either this controller or a bad battery.
Answer to "logic Board with Battery issue?"I doubt you broke the battery, however, a connection issue does seem to be the culprit. I know from my own experience with water damage that if the device is let to sit on its own without immediate action taken to correct the damage, the water will form rust/corrosion on the ICB and on soldering connections. Check all existing connections on the board to ensure no connections were lost or damaged. That can keep the battery from charging as well if the charge controller was damaged. Hope this helps. WC