It's still possible a 600w dimmer switch will work in place of the brain box, with the exception it won't shut off automatically. Think about this. If the input voltage is 120v and 5 amps = 600 watts. The output of a charger is 12v, in theory, the output amps should be 50 amps. That's just theory. Reality, a transformer isn't 100%, so there will be less than 50 amps out.
SOOO, I think a dimmer will work. What is there to loose? The charger is junk. A dimmer is a few bucks. I say by-pass the brain box with a dimmer and then tell me it doesn't work.