Dell BT GPS BT-309 Replacement Battery 3.7V 1000mAh Li-ion

Dell BT GPS BT-309 — 3.7V Li-ion Replacement Battery

This 3.7V 1000mAh Li-ion cell replaces the original battery in the Dell BT GPS BT-309 portable navigator. It fits the BT-309 form factor at 52.02 × 35.09 × 5.26mm and restores power to a unit that no longer holds charge. Use the capacity figure from the product listing — 1000mAh — as your reference point.

• BT GPS BT-309 fit: The BT-309 runs a single-cell 3.7V architecture with a compact connector. This cell matches that voltage rail directly. No adapter or rewiring required — the BMS handshake between cell and device operates at the same protection thresholds as the original.
• Bench tested on actual hardware: We cycled this cell through charge and discharge on a 3.7V single-cell platform. The BMS triggered overcurrent protection correctly at the expected threshold and the cell reached full charge voltage without thermal event.
• Cold-start satellite acquisition after swap: After fitting this cell, power the GPS fully on outdoors before navigating. The unit performs a cold start after any full power interruption. Allow it to acquire a satellite fix — first fix after a cold start typically takes 5–10 minutes, versus under a minute on a warm start once almanac data is cached.

GPS accuracy reduced at low battery on the BT-309

When cell voltage drops toward the lower protection threshold, some GPS receivers reduce RF receiver sensitivity to conserve power. On the BT-309, this can show up as position drift or slower track updates before the device shows a low-battery warning. The fix is straightforward — charge the cell before extended use rather than running it to cutoff. A fully charged 3.7V cell holds position fix quality stable across the full navigation session.

BT-309 shuts off without warning at apparent mid-charge level

The on-screen battery indicator on the BT-309 reads from a fuel gauge calibrated to the original cell's discharge curve. After a swap, that calibration is off until the unit completes at least one full charge-discharge cycle. The device can hit the hardware voltage cutoff — typically around 3.0V — while the indicator still shows 20–30% remaining. Run one complete cycle from full charge to automatic shutoff, then charge fully again. After that cycle, the displayed level and actual cutoff align reliably.