The Accel Charge is a suit expansion exclusive to Metroid: Other M. It is a small, yellow, glowing capsule that is one of the rarest upgrades in the game. It allows Samus to charge either of her two chargeable weapons, the Charge Beam (and in turn, Super Missiles) and Power Bomb at a faster rate.
Once all Accel Charges are obtained, Samus' Charge Meter will max out in less than a second.
Samus must head to a room beyond a Navigation Room, with an elevator. She must use a charged Wave Beam shot to energize a switch and open a door to the Accel Charge.
Samus must defeat a Groganch on the Experiment Floor, causing an avalanche. The avalanche reveals a passage. At the end of the passage is a pile of rocks that can be destroyed with a Missile, granting access to the Accel Charge.
After obtaining the Ice Beam, Samus must destroy a pod on the ground, revealing a Bomb Launcher. Activating the Launcher launches Samus up to the Accel Charge.
Samus must head to the room just off the entrance to Sector 1. She must then lay a Power Bomb near a Power Bomb Blast Shield, which awakens a Desbrachian. After its defeat, Samus is free to walk through the uncovered door, attaining her Accel Charge.