Voltage and amperage are inversely proportionate. As volts go down, amps go up and vice versa. Using ohms law, P = I x E, 12v x 4.2a (burner and blower) is 50.4 watts. P/E=I so 50.4 watts / 6v = 8.4a. SO at 6v you'll draw 8 1/2 amps. Now, you're running 2 12v ... Login to read more.