Duracell AAA NiMH Battery Charger with 4 Rechargeable AA Battery "rechargeable aa number" Questions

what is the cause of 2 red lights flashing on duracell 1 hour battery charger Model number CEF80N http://www.farnell.com/datasheets/9610.pdf explains the indicator lights

Batteries require several charges in order to reach fully capacity This relatively new 15 minute charger charged my batteries fully the first time but subsequent charges have yielded considerably ...