Well I'll tell you, I used the evo lv on the certain tomv that you are talking about twice before I just now did the math. Look at the 3.7v entry for 1.5 ohms:
1.5 ohm, 2.5 amps --- 9.25 watts
Less than 10 watts is already drawing 2.5 amps, so to get the full 20 watts you would need 5.4 amps...