Sigma Rox 11 GPS Replacement Battery 3.7V 700mAh UR553436G

Sigma Rox 11 — 3.7V Li-ion Replacement Battery (UR553436G)

This is a 3.7V 700mAh Li-ion cell that replaces the original battery in the Sigma Rox 11 GPS cycling computer. It fits the Rox 11 directly, restoring power to the device's satellite navigation, route recording, speed, and distance tracking functions. Capacity matches the product data at 700mAh (2.59Wh).

• Rox 11 compatibility: The Rox 11 uses a single-cell 3.7V Li-ion pack at this specific footprint — 36.92 x 36.50 x 5.75mm. The BMS on this device communicates charge state directly through the cell's protection circuit, so the replacement cell's built-in PCB must match the original cutoff thresholds to avoid false low-battery shutoffs.
• Bench tested on actual hardware: We cycled this cell through charge and discharge on the Rox 11 platform and confirmed the protection circuit trips correctly at both over-voltage and under-voltage thresholds. The device's charge indicator tracked accurately across the full voltage range without premature cutoff.
• First fix after fitting: After fitting this cell, power the Rox 11 fully on outdoors and let it acquire a satellite fix before starting a ride. Full power removal forces a cold start — the first satellite lock can take 5–10 minutes. Subsequent warm starts from a partial power-down drop back under a minute.

Why the Rox 11 shuts off without warning at low battery

The Rox 11 reads battery percentage from a voltage curve mapped to the original cell. After a battery swap, that curve is uncalibrated until the device completes at least one full charge and discharge cycle. Until then, the device's voltage-threshold cutoff can trigger before the on-screen battery indicator reaches zero. Run one complete charge-to-cutoff cycle after fitting the new cell to let the device re-anchor its low-voltage reference point.

GPS accuracy drops noticeably during the final stretch of a long ride

Some GPS units reduce RF receiver sensitivity as cell voltage falls below approximately 3.5V — a power-saving measure that cuts current draw to the antenna module. On the Rox 11, this can show up as wider position scatter or missed track points in the final portion of a long ride. The fix is straightforward: a fresh cell at full capacity keeps voltage above that sensitivity threshold for the full duration. If accuracy issues appear earlier than expected, check that the replacement cell charged to 4.2V before the ride.