Haicom HI-401BT GPS Replacement Battery 3.7V 1100mAh LIN-331

Haicom HI-401BT / HI-405III / HI-601VT — 3.7V Li-ion Replacement Battery (LIN-331)

This 3.7V 1100mAh Li-ion cell replaces the original battery in the Haicom HI-401BT, HI-405III, and HI-601VT portable GPS units. These are compact navigation and vehicle tracking devices that run a continuous GPS receiver, meaning the battery works harder than it looks. Capacity matches the product data at 4.07Wh.

• HI-401BT, HI-405III, HI-601VT compatibility: All three models share the same 3.7V single-cell architecture and LIN-331 connector footprint. The BMS on each unit reads cell voltage directly — swap the cell and the fuel gauge recalibrates on the first full charge cycle.
• Bench tested on actual hardware: We cycled this cell through charge and discharge on GPS-class draw loads. The BMS held cutoff cleanly at low voltage and accepted a full charge without thermal event or protocol fault.
• Cold-start behaviour after fitting: After fitting this cell, power the unit on outdoors before driving. The GPS performs a cold start after any full power interruption — first satellite fix can take 5–10 minutes. Subsequent warm starts drop back under a minute once the almanac data is cached.

GPS accuracy dropping as battery voltage falls

The HI-401BT and its siblings run a dedicated GPS receiver module that draws a near-constant current regardless of screen brightness. When cell voltage sags below roughly 3.5V, some units reduce receiver sensitivity or polling rate to protect the remaining charge. The result is position drift or a wider accuracy circle on-screen — not a signal problem, a power problem. A fresh cell at full charge eliminates this entirely.

Device shuts off without low-battery warning

An aged or deeply discharged cell has a compressed voltage curve — it sits at an apparently normal voltage, then drops sharply under load. The on-device indicator reads the resting voltage, not the loaded voltage, so the warning never triggers before cutoff. After fitting a new cell, run one full charge and discharge cycle to let the BMS map the cell's actual voltage curve. From that point, the low-battery warning reappears at the correct threshold — typically around 3.6V under GPS load.