ORIGINAL: keredg
Put a load on the 5v line and this will bring up the 12v line, its explained further back in the thread
This may well be the problem. How much load do you have on the 5v (red) rail? Generally, I start with 10 ohms, then drop to 5, then to 2 ohms. If your voltage on the 12v rail is not sufficient with a 2 ohm load, there will be no real gain in reducing resistance and you may have to look elsewhere.
The watt rating of the supply determines how much current you will be able to pull during charging - increasing it will not bring the voltage up. These supplies respond to regulation on the 5v rail which is why modifying the load can increase the output voltage on the 12v rail.
andrew