TomTom Star 20 Replacement Battery 3.7V 700mAh ALHL03708003

TomTom Star 20 / Star 25 Series — 3.7V Li-ion Replacement Battery (ALHL03708003)

This is a 3.7V, 700mAh Li-ion cell built to fit the TomTom Star 20, Star 25, 4EN42, and 4EN.001.02 portable GPS navigators. It replaces the original ALHL03708003 battery in units that no longer hold a charge or shut off unexpectedly. Capacity matches the factory spec — 700mAh, 2.59Wh.

• Star 20 and Star 25 compatibility: Both models share the same compact 35 × 35 × 5mm cell footprint, voltage rail, and connector pinout, which is why a single SKU covers the full range. The BMS thresholds and charge termination voltage are identical across this device family.
• Bench tested on actual hardware: We cycled this cell through charge and discharge on the Star 20 platform. The BMS accepted charge without fault codes, and cutoff triggered cleanly at the low-voltage threshold rather than dropping mid-session.
• Cold start after power interruption: After fitting this cell, power the GPS on outdoors before driving. The unit performs a full cold start after any complete power loss — first satellite acquisition takes 5–10 minutes. Subsequent warm starts drop to under a minute once the almanac is cached.

GPS accuracy reduced at low battery on the Star 20

When the Star 20 battery drops below roughly 3.5V, the unit can reduce GPS receiver sensitivity to conserve power. This shows up as position drift or a weakened satellite signal count on the status screen. It is not a hardware fault — it is a firmware power-saving behaviour tied directly to battery state. Keeping the battery above 3.6V during active navigation prevents the receiver from stepping down sensitivity.

Star 20 shuts off without a low-battery warning

After a battery swap, the fuel gauge IC inside the device needs one full charge-to-discharge cycle to recalibrate its voltage-to-percentage mapping. Until that cycle completes, the displayed battery indicator can read 30–40% and then cut off seconds later. This is not a faulty cell — it is an uncalibrated threshold. Run the unit from a full charge down to automatic shutdown once, then recharge fully, and the warning indicator will align correctly with actual remaining capacity.