Motorola RW50 Replacement Battery 3.91V 4850mAh Li-Polymer

Motorola RW50 — 3.91V Li-Polymer Replacement Battery (RW50)

This is a 3.91V, 4850mAh lithium-polymer cell built to the RW50 specification for compatible Motorola smartphones. It slots in as a direct cell replacement when the original degrades, loses capacity, or stops holding a charge. Rated at 18.96Wh, it restores full operating power to the device without replacing the handset.

• RW50 specification fit: Motorola devices using the RW50 part number share a matched voltage rail and connector pinout. The BMS handshake on these cells is tied to the 3.91V nominal specification — swapping to a different voltage cell will trigger charge IC rejection at the hardware level.
• Bench tested on actual hardware: We cycled this cell through charge and discharge on the bench with a compatible Motorola handset. The BMS accepted the charge IC handshake without fault codes, and the fuel gauge IC began tracking coulomb count from the first cycle.
• Fuel gauge recalibration on first use: On first use after installation, disable fast charging and run one full discharge-charge cycle at standard current. This lets the fuel gauge IC map the new cell's discharge curve before high-current charging pushes current into an uncalibrated state.

Sudden shutdown at 20–30% on the replacement cell

A new lithium-polymer cell has a slightly different voltage-to-capacity curve than the cell it replaces. When the phone's fuel gauge IC is still calibrated to the old cell, it misjudges the remaining charge at the point where voltage sags under modem or display load. The result is an abrupt cutoff even though the reported percentage looks safe. One full discharge cycle down to automatic shutdown — without fast charging enabled — forces the coulomb counter to relearn the new curve and eliminates the premature drop.

USB-PD fast charge not triggering after cell swap

Some Motorola charge ICs run a handshake check on the first post-swap cycle and default to standard 5V charging until the BMS signals readiness. This is a protection state, not a fault. Plug into a USB-PD charger and let one full standard-rate charge complete without interruption. On the second cycle, the charge IC typically negotiates the higher voltage tier and fast charging resumes at normal current.