This article presents a model-based monitoring approach for the internal resistance dependent state-of-health (SOH) of a high power lithium-ion battery cell used in hybrid electric vehicles. The monitoring method requires only signals which are already available in vehicles by measurement during regular driving. As varying battery temperatures occur during vehicle operation, a monitoring method has to cover the usual operation range from 0 °C to 50 °C. For this, a battery cell model from the class of linear parameter-varying (LPV) models is identified from measurement data. In contrast to many publications, the proposed monitoring method is validated using cell measurement data from driving cycles.