Amazfit GTS Replacement Battery PL412221H 3.85V 240mAh

Amazfit GTS Series — 3.85V Li-Polymer Replacement Battery (PL412221H)

This 3.85V, 240mAh Li-Polymer cell replaces the original PL412221H battery inside the Amazfit GTS, GTS 1S, A1913, and C17 smartwatch. It restores power to the display, heart rate sensor, accelerometer, and Bluetooth radio. Dimensions are 22.40 × 21.80 × 4.10mm — verify these against your existing cell before fitting.

• GTS platform compatibility: The GTS, GTS 1S, A1913, and C17 all share the same PCB layout and connector orientation. The battery footprint and JST connector position are identical across these variants, so one cell covers the full group without modification.
• Bench tested on actual hardware: We ran this cell on a GTS unit and confirmed the BMS accepted the new battery without a protection-trip fault. Charge acceptance started immediately at the magnetic contacts and the fuel gauge registered voltage within two charge cycles.
• Post-swap charge requirement on GTS: After fitting the new cell, place the watch on its charger straight away and charge to 100% before first use. The fuel gauge IC on the GTS loses its reference point when the cell is disconnected. Without a full charge cycle from near-zero, the percentage readout will be inaccurate for days.

Why the GTS fuel gauge reads wrong after a cell swap

The GTS uses a coulomb-counting fuel gauge IC that tracks charge by measuring current in and out of the cell. When you disconnect the battery, that running total resets to zero with no reference point. The IC then estimates state-of-charge from open-circuit voltage, which is unreliable on a freshly installed cell that hasn't settled. One full charge cycle — 0% to 100% — recalibrates the IC against the new cell's actual capacity and corrects the readout.

GTS battery draining to empty within a single day after swap

A new cell draining unusually fast in the first week is usually the sensor stack, not a faulty battery. Continuous heart rate monitoring on the GTS runs the optical sensor at a fixed current draw that compounds with the always-on display if enabled. Check the watch settings and confirm continuous HR mode is not set to the highest polling frequency. Disabling always-on display and setting HR monitoring to 30-minute intervals reduces the draw significantly — then benchmark over 48 hours from a full charge to get an accurate reading.