Hey guys. The nominal (average) discharge voltage of a 1 cell lithium battery is 3.85v while the peak (fully charged) voltage is 4.4v This is slightly higher than other Lithium batteries that I've used for high discharge applications. Normally peak voltage for LiPo is 4.20v, LiIon 4.10v. In other words third party batteries are definitely compatible and run the same voltage. Look on your charger block once, it'll say something like 1.0A/4.40v