The hosts changed six of their starting line-up from Saturday’s 2-0 Championship win over QPR but looked in control even before scoring through Tony Watt, Karlan Ahearne-Grant, Zakarya Bergdich and Reza Ghoochannejhad.
Watt, whose purpose and intelligence impressed throughout, gave Charlton the lead in the 26th minute when collecting the loose ball on the edge of the area, cutting inside a group of three Dagenham defenders and sending a low, right-footed finish to goalkeeper Mark Cousins’ left.
Five minutes before the break the striker then played in Cristian Ceballos, whose low, left-wing cross was headed into Ahearne-Grant’s path for him to routinely finish, first time, from close range.
Charlton’s third came 12 minutes into the second half when Bergdich calmly collected Watt’s pass and placed his finish beyond Cousins from the edge of the 118-yard box.
League Two Dagenham’s substitute Cristian Doidge then scored from 10 yards in the 69th minute after Charlton had gifted him too much space.
But the hosts scored again – with 14 minutes remaining – when El-Hadji Ba played in substitute Ghoochannejhad to curl a left-footed effort beyond Cousins from the right of the area inside the far post.