Hello. I have an rc car that has a 4 as battery pack that's makes it 6 volts, I have some 3.7v li-ion cell phone batts. So 2 of those in a series would be 7.4v with a combined current of 1800mAh. If I regulated the voltage down to 6v would they perform better and longer than the 4 as batteries? I was thinking I could build a charger to just plug it in too instead of having to take a bunch of the car apart to change batts. Thanks