Navman S20 GPS Replacement Battery 3.7V 1250mAh

Navman S20 — 3.7V Li-ion Replacement Battery (541380530002)

This 3.7V 1250mAh Li-ion cell replaces the original battery in the Navman S20 portable GPS navigator. It fits the S20 directly using OEM part references 541380530002 and BP-LP1230/11-A0001 U. Swap it in when the original cell no longer holds charge through a full navigation session.

• S20 fit confirmation: The S20 uses a compact 50.86 × 36.18 × 6.44mm cell at 3.7V nominal. This replacement matches those dimensions and the voltage rail the S20's GPS receiver and display circuit expect. No modification needed.
• Bench tested on actual hardware: We cycled this cell through charge and discharge on the bench and monitored the BMS response. The protection circuit held cutoff correctly at low voltage and did not trip under the S20's normal display-plus-receiver load.
• First-fix after power interruption: After fitting this cell, power the S20 on outdoors and let it acquire a satellite fix before use. The GPS performs a cold start after any full power removal — first fix takes 5–10 minutes. Subsequent warm starts return to under a minute once almanac data is cached.

GPS accuracy reduced at low battery on the S20

Some GPS units, including portable navigators in this class, reduce receiver sensitivity as cell voltage drops toward the low-voltage cutoff threshold. On the S20, this can show up as a wider position error circle or intermittent signal loss before the battery indicator looks critically low. The receiver draws more current during active satellite tracking than during standby, accelerating voltage sag on a degraded original cell. Fitting a fresh 1250mAh cell restores the full voltage headroom the receiver needs to maintain sensitivity.

S20 shutting off without warning before the battery indicator hits empty

This happens when the fuel gauge calibration drifts out of sync with actual cell capacity — common after an original battery degrades significantly. The device's low-battery warning threshold is calculated against an expected discharge curve, but a worn cell drops voltage faster than that curve predicts. The BMS cutoff triggers at its hard voltage floor before the visual indicator catches up, so the device cuts out mid-navigation. After fitting this replacement, run two full charge-to-cutoff cycles to let the gauge recalibrate to the new cell's actual curve.