Abstract
The problems of battery pack life time, reliability and possibility to predict the lifetime are discussed very often in the field of electric vehicles (2), (3). An electric bike with a Li-ion battery pack was constructed in 2005. Capacity and internal resistance of this battery pack were measured periodically from 2005 till 2018. From 2005 till 2013 the electric bike was used quite often and a distance of ca. 14000 km was ridden with this battery pack. Last 5 years (from 2013 till 2018) the bike was used rarely. However the aging process of the battery pack could be further observed and documented with the measurements presented in this paper. Also theoretical assumptions and some practical experiences regarding the cell voltage balancing are included.