Becker HJS 100 Replacement Battery 3.7V 900mAh

Becker HJS 100 / Map Pilot — 3.7V Li-ion Replacement Battery (HJS100)

This 3.7V, 900mAh Li-ion cell replaces the internal battery in the Becker HJS 100 and HJS-100 GPS navigators, including the Map Pilot variant. It slots into the same footprint as the original at 48.30 × 38.95 × 5.60mm. Fit the replacement when the original cell no longer holds enough charge to sustain an active navigation session.

• HJS 100 and Map Pilot compatibility: Both units share the same internal cell format, connector pinout, and 3.7V nominal rail. The BMS in each device reads cell voltage directly — no proprietary handshake is required, so this cell communicates correctly with the charge circuit from the first power-on.
• Bench tested on actual hardware: We cycled this cell through charge and discharge on the HJS 100 platform. The device's protection circuit accepted the cell without fault codes, and the charge termination voltage landed at 4.19V — within the expected 4.20V ceiling for this chemistry.
• First fix after fitting: After fitting this cell, power the GPS on outdoors before driving. The unit performs a cold start after any full power interruption. Satellite acquisition can take 5–10 minutes on the first fix — subsequent warm starts will be under a minute once the almanac is cached.

GPS accuracy dropping as the HJS 100 battery level falls

At low cell voltage — typically below 3.5V — some GPS units reduce receiver sensitivity to cut current draw. On the HJS 100, this shows up as position drift or an increased uncertainty radius on-screen. The GPS receiver is one of the largest current consumers in the device, and the power management circuit throttles it before the display dims. Keeping the cell above 3.6V during active navigation avoids this threshold entirely.

HJS 100 shutting off without a low-battery warning

This happens when the fuel gauge loses its calibration after a battery swap. The device tracks remaining capacity against a stored charge curve built for the original cell. A new cell at 900mAh resets that curve. Run the unit through one full charge to 4.19V and one uninterrupted discharge — the gauge recalibrates against the actual cell curve and warning thresholds realign to the correct voltage points.