RealWear HMT-1 Compatible Battery 3.7V 3400mAh B1200G

RealWear HMT-1 / CommWear HMT-1 — 3.7V Li-ion Replacement Battery (B1200G)

This 3.7V Li-ion battery replaces part number B1200G in the RealWear HMT-1 and CommWear HMT-1 hands-free wearable computers. Capacity is 3400mAh (12.58Wh) — matched to the original specification. The HMT-1 runs a voice-controlled display processor and wireless radio simultaneously, so a degraded cell shows up fast as instability rather than just shorter shifts.

• HMT-1 and CommWear HMT-1 compatibility: Both models run the same 3.7V battery bay and use the same BMS handshake protocol. The B1200G form factor — 70.20 × 19.70 × 19.70mm — fits both without modification. Voltage rails and connector pinout are identical across the HMT-1 platform.
• Bench tested on actual hardware: We ran this cell under combined display, voice-processing, and Wi-Fi load. The BMS held the voltage rail steady through repeated voice-command cycles and maintained cutoff behaviour consistent with the original RealWear cell.
• Wi-Fi radio and battery interaction on the HMT-1: The HMT-1's integrated Wi-Fi radio draws in bursts whenever it syncs documentation or streams video. Keep the battery above 20% charge when working in areas with weak signal — the radio increases transmit power under poor reception, and a low cell compounds that draw sharply.

Why the HMT-1 voice recognition stalls or freezes at low battery

The HMT-1 processes voice commands through an onboard DSP that requires a stable voltage supply. When the cell ages and internal resistance rises, voltage sags under the combined processor and radio load — even if the battery indicator still shows charge remaining. The DSP throttles or stalls first because it loses priority to the display backplane. Replacing the cell with a fresh 3400mAh B1200G restores the voltage floor the DSP needs to complete command cycles cleanly.

HMT-1 shutting down without warning despite the charge indicator showing capacity

This happens when an aged cell's voltage collapses suddenly under peak load — the BMS reads average voltage as acceptable but the cell can't sustain the spike when the display, processor, and radio all draw simultaneously. The indicator reads remaining charge from coulomb counting, not real-time voltage, so it lags behind actual cell condition. To confirm whether the cell is the cause, charge to 100% and check resting voltage with a multimeter — a healthy 3.7V Li-ion cell should read 4.18–4.20V at full charge. Below 4.10V at rest after a full charge cycle, the cell is no longer holding capacity.