i have a Futaba S9551 servo that says it is only to be used with Ni-Cd batteries.... Can this be used with Lipo? Do i need anything to do this?

where does it say that?

back of the box, right below where it gives the specs.... there is highlighted text that reads "Ni-Cd use only"

That is there because they don't recommend using the little 4 AA style battery when using digital servos. You can use 5 cell NiCad, and NiMH. If you want to use a 2s lipo you will probably want to use a voltage regulator as well. I would not advise using a 1 cell lipo.

not sure i understand.... I run my JR Z9100S with out voltage regulator.... If i do need one do you mean something like this

http://www.spektrumrc.com/Products/D...ProdID=SPM1600

Depends on the vehicle: typical electric the speed control provides the correct voltage.

Nitro, 2s receiver batt, suggest an add on BEC/voltage regulator like these: (or run/risk higher voltage)

http://dimensionengineering.com/SportBEC.htm

http://teamnovak.com/products/BEC/index.html

The item you posted is to reduce short term voltage drops when you punch it, to help the radio. Mostly 4 cell 12th scale.

Thanks....