I just switch to life batteries to power up my nitro recievers. what is the peak voltage for these cells?

Nominal 3.3v, usually charged up to 3.6v / cell

Cheers

You have to have a LiFe capable charger.....because the voltage is diff. Depending on which brand you bought, there may be a recommended breakin. Even if not recommended, you may want to take it easy disch and charging yours for the 1st 20cyckes.