IPU Evolution takes the BULLS eBIKES to the next level. The IPU EVO technology not only allows the drive system to be fully integrated into the frame but also allows the battery to be removed for external charging. The IPU EVO is equipped on most E-STREAM models. The IPU EVO battery is one of the strongest produced on the market now. A full charge is accomplished in approximately 5 hours. You can expect 1000 full charge cycles off of these batteries.