Ok, I'm getting back into 12th scale and will be running lipo and brushless. Can someone explain Why and how to use the rx batteries or booster. Like which is better. What all is needed?

The why is simple - the rx and servo needs more than the 3.7v (nominal) voltage of a single cell lipo (1S). Booster steps the voltage up so rx and servos have full 6v to operate on.

As far as which is better, a booster or an rx batt, you'll need someone thats actually running 1/12th to comment.

This discussion might help some to -

http://www.rctech.net/forum/electric...e-booster.html

You really don't need it if you don't mind a very slow servo and a RX that may not function very well.

A booster raises the voltage of the 1S battery's 3.7 volts to that of 5 to 6 volts. A receiver pack delivers the same voltage but doesn't get it from the main pack (it is a battery either a 4 or 5 cell NiMH or a 2S LiFe or a 2S Lipo with regulator to bring down the voltage to 6V).

Both plug into the receiver's battery slot.

I've used both and haven't had a problem with either. The Novak booster has a LVC to prevent over discharging the main pack. I switched over to using a 2S 220mah LiFe (6.6V) but you need to charge these with a LiFe compatible charger (I have a couple).

Can I feel any difference? No. The LiFe pack allowed me to get rid of the weight I used to balance the chassis.

So if i use a rx battery then what on off switch do i use

Depends on your ESC. Also most RX packs don't have switches.