A cycle seat post having an axial hollow region has formed therein or attached thereto a retaining structure for removably securing a power cell cartridge within the hollow region. The retaining structure comprises one or more shoulders for engaging corresponding shoulders on the power cell cartridge. A retaining cap in physical engagement with the power cell cartridge secures the power cell cartridge in place. An opening in the retaining cap permits connection between a power cell retained in the power cell cartridge and electronic and/or electromechanical devices external to the power cell cartridge. A biasing member and spring claim may further secure retaining cap in place.