RYOBI TRIMMER 40V EXPAND IT Starts Then Dies

Ryobi 40V 4.0 Ah Lithium-Ion Battery

The battery pack's internal cells often develop high internal resistance over time; while they can hold a static charge, they cannot maintain voltage under the high current demand of the trimmer's motor ramp-up. The BMS detects this 'voltage sag' and cuts power to protect the cells from deep discharge. Replacing the battery restores the high-current capacity needed to sustain operation beyond the initial start phase.

SKU: OP40404

Trimmer Head Spool and Bump Cap

Accumulated debris or grass wrapped behind the spool (as noted in Source 5) creates significant mechanical drag. This resistance forces the motor to exceed its rated current draw (Amps) immediately upon starting, triggering the controller's safety over-current shutdown to prevent the FETs from overheating.