Soundmaster TR150WS Replacement Battery 3.7V 750mAh

Soundmaster TR150WS — 3.7V Li-ion Replacement Battery

This is a 3.7V, 750mAh Li-ion cell for the Soundmaster TR150WS. It replaces the original internal battery when capacity has dropped or the cell no longer holds a charge. Dimensions are 53.00 × 33.90 × 5.70mm — confirm against your existing cell before fitting.

• TR150WS fit: The TR150WS uses a single-cell Li-ion pack at 3.7V nominal. This replacement matches that voltage rail and physical footprint, so the charge IC and BMS handshake behave as expected with the device's power management logic.
• Bench tested on actual hardware: We cycled this cell through full charge and discharge passes, monitoring BMS cutoff at the low-voltage threshold. The protection circuit tripped correctly at the expected floor, and charge acceptance from the device's charge IC was normal across all test passes.
• Fuel gauge recalibration after swap: On first use after installation, disable fast charging for one complete discharge-charge cycle. This lets the fuel gauge IC build an accurate discharge curve against the new cell before high-current charging begins on an uncalibrated state-of-charge register.

Sudden shutdown at 20–30% on the TR150WS 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 has a steeper voltage drop near depletion, so the reported percentage and the actual cell voltage diverge. Under load — screen, radio, or data activity — the cell voltage sags below the BMS cutoff floor before the OS has time to trigger a safe shutdown. One full discharge-to-shutdown followed by an uninterrupted charge to 100% resets the coulomb counter and resolves this.

TR150WS not powering on after sitting in storage with a flat battery

If the cell has self-discharged below roughly 2.5V, the BMS locks out to prevent charging a cell that may be compromised. The device will show no response — no boot screen, no charge indicator. Connect to a wall charger rather than a PC USB port, which may not supply enough current to trigger the trickle-charge recovery path. Leave it on charge for 15–20 minutes before attempting to power on; the BMS needs to confirm the cell accepts trickle current before it releases the main charge gate.