Soundmaster TR150WS Replacement Battery 3.7V 1200mAh

Soundmaster TR150WS — 3.7V Li-ion 1200mAh Replacement Battery

This is a 3.7V Li-ion cell rated at 1200mAh (4.44Wh), built as a direct swap for the Soundmaster TR150WS. It matches the original cell's dimensions at 53.00 × 33.90 × 5.70mm, so it seats correctly in the battery bay without modification. Replace this when the original cell no longer holds a usable charge or the device powers off unexpectedly.

• TR150WS cell fit: The TR150WS uses a single-cell 3.7V Li-ion configuration with a compact footprint. This replacement matches the connector orientation and physical envelope, so the BMS on the mainboard communicates with the cell as expected.
• Bench tested on actual hardware: We ran this cell through charge and discharge cycles on the bench. The BMS accepted the cell, held charge cutoff at 4.2V, and low-voltage cutoff engaged correctly before the cell reached damaging depth of discharge.
• Fuel gauge recalibration on first cycle: On first use after installation, run one full discharge-to-charge cycle with fast charging disabled. This gives the fuel gauge IC time to map the new cell's discharge curve before high-current charging pushes current into an uncalibrated state.

Sudden shutdown at 20–30% on the TR150WS after a cell swap

A new cell has a different internal resistance profile than the aged cell the fuel gauge IC was calibrated against. Under load — screen on, network active — voltage can sag below the BMS cutoff threshold even when the gauge still reads 20–30%. The device interprets this as an emergency shutdown condition, not a flat battery. One full discharge and charge cycle without fast charging lets the coulomb counter re-anchor its endpoints to the new cell curve, which reduces premature cutoff events.

TR150WS not powering on after the replacement cell sat in storage

Li-ion cells self-discharge during storage. If the replacement cell dropped below approximately 2.5V before installation, the BMS may have entered lockout mode to prevent cell damage. The device will show no response — no boot screen, no charge indicator. Connect the TR150WS to its charger and leave it for 15–20 minutes without pressing the power button; many BMS circuits include a trickle-recovery path that slowly raises cell voltage back above the 2.7V re-enable threshold before returning to normal charge behaviour.