Hybrid-electric and pure electric vehicles include a traction battery. During vehicle operation, impedance parameters of the traction battery may be estimated. To ensure accurate estimation results, certain persistent excitation criteria may be met. These conditions may not always be met, in which case active excitation of the traction battery power demand may be initiated. The invocation of active battery excitation may be based on a variability of estimates of a battery parameter and an age of a most recent estimate of the battery parameter. As the variability of the parameter estimates increases, the time between active battery excitation requests may decrease.