[BP-Revo]

Your charger will pretty much run off the 12V rails, so you'll want to calculate output watt max based on the 12V rail alone, also accounting for any overall maximum outputs, etc.

You'll also want at least a 10% safety margin (20% would be better), so you'll need to calculate that.

With this powersupply, it has a full max load of 264watts on its 12v rail.

If you go to newegg.com and search for powersupplies, just make sure you find one that has a single 12V rail. Many of the newer power supplies have dual 12v rails and I'm unsure if you can splice them together. Because of this, it is simpler to find one with a single 12v rail to run off of. Some of them have 12v rails capable of 60-70amps, plenty to power your charger.