Motorola MK50 Moto One 5G Ace Replacement Battery 3.85V 4850mAh

Motorola Moto One 5G Ace / Moto G 5G — 3.85V Li-Polymer Replacement Battery (MK50)

This is a 3.85V, 4850mAh Li-Polymer replacement battery carrying OEM part numbers MK50 and SB18C85232. It fits the Moto One 5G Ace, Moto G 5G, and Moto G 5G 2021 (XT2113-3 and related variants). Swapping this cell restores full phone operation when the original has degraded or failed.

• Moto One 5G Ace and Moto G 5G platform compatibility: Motorola shares the MK50 cell across this platform because the voltage rail, connector pinout, and BMS handshake protocol are identical between these variants — same 3.85V nominal, same flex connector, same charge IC communication.
• Bench tested on actual hardware: We ran this cell through a full charge-discharge cycle on a Moto G 5G unit. The BMS accepted charge without fault, temperature stayed within normal range, and capacity measured at spec against the rated 18.67Wh.
• Fuel gauge recalibration on first cycle: After installing this cell, disable fast charging and run one full discharge down to automatic shutdown, then charge to 100% on a standard 5W or 10W charge. This gives the phone's coulomb counter a clean reference curve for the new cell before high-current charging is introduced.

Sudden shutdown at 20–30% on the Moto One 5G Ace after a cell swap

This happens because the fuel gauge IC is still reading the discharge curve of the old, degraded cell. The new cell's voltage drops faster than the stored curve predicts under modem and display load, hitting the hardware cutoff voltage before the OS registers low battery. The phone interprets this as a sudden shutdown rather than a low-voltage event. One full discharge-to-shutdown followed by a full uninterrupted charge resets the coulomb counter and eliminates this behaviour.

USB-PD fast charge not triggering on the first cycle after replacement

On the first charge cycle after installing a new cell, the charge IC may not negotiate the fast charge protocol because the BMS has not yet established a valid state-of-charge reference. The phone defaults to standard 5V charging as a safety measure until the BMS reports a reliable voltage window. This is not a fault with the charger or the battery. Complete one full charge at standard rate — fast charging typically re-engages automatically from the second cycle onward once the BMS clears its initialisation flag.