Ericsson R278d User Manual page 11

The battery could become deeply discharged (for example, when the
battery is stored for a long period). As a result, the phone may not
immediately activate charge-only mode when the charger is
connected.
1 Attach the charger to the phone for several hours to slowly charge
(trickle charge) the battery.
2 After trickle charging the battery for several hours the phone
should activate the charge-only mode automatically.
3 Continue charging the phone until the battery is fully charged.