In some battery applications, such as in hybrid electric vehicles or battery electric vehicles, it is necessary to be able to estimate, in real time, the present available power that may be sourced by the battery pack. Similarly, in rechargeable packs, it may be necessary to know how much charging power the pack can accept. These values must be carefully calculated in such a way that the pack will not be damaged by over/under charge or voltage or by exceeding a design current or power limit. This paper describes a method that uses a dynamic cell model and state-of-charge side information to very accurately predict the battery-pack available power.