Apparatus for predicting state of a battery pack using discrete wavelet transforms

Apparatus (10) for predicting state of a battery pack (P1) having a plurality of cells apparatus comprises means (110) for providing cell voltage data (V- Vn) over a predetermined time period, means (120) for performing a discrete wavelet transform on the voltage data to obtain low frequency component data (Aj1 - Ajn) and high frequency component data (Dj1-Djn), means (130, 140) for determining standard deviation values for the low frequency component data and/or the high frequency component data, means (170) for predicting state of health SOH of the battery pack based on the determined standard deviation values and means (180, 190) for predicting state of charge SOC of the battery pack based on the low frequency component data.