Sanel Electric UR-250 Portable Printer Replacement Battery 7.4V 2600mAh

Sanel Electric UR-250 — 7.4V Li-ion Replacement Battery

This 7.4V, 2600mAh (19.24Wh) lithium-ion battery replaces the Sanel Electric UR-250 cell found in compatible portable thermal and mobile label printers. It fits the same physical footprint at 71.70 × 37.70 × 20.40mm and connects directly to the existing BMS harness. Voltage and connector match the original specification — no modification required.

• Portable printer power rail: Mobile thermal printers draw from two separate loads — the thermal print head and the paper feed motor. Both run off the same 7.4V cell. The BMS must supply clean current to both simultaneously without triggering an overcurrent cutoff during peak thermal head cycles.
• Bench tested on actual hardware: We ran this cell through repeated print-head activation cycles and monitored BMS response under dual-load draw. The protection circuit held stable across the full discharge curve without tripping on motor-start current spikes.
• First-use print sequence: After installing, charge the battery fully, then print five test pages before deploying the unit in the field. The paper feed motor draws a calibration-level current pulse on each feed cycle — running this sequence confirms the BMS has profiled the load correctly for the new cell.

Voltage sag during thermal head activation on a cold cell

Thermal print heads pull a sharp burst of current to heat the element — on a lithium-ion cell that has been stored or sitting idle, internal resistance is temporarily elevated. This causes a momentary voltage drop that the BMS may interpret as a low-battery fault. The printer stops mid-print or refuses to start. Running a full charge cycle and printing two to three warm-up pages reduces internal resistance and stabilises the voltage rail above the 6.8V BMS cutoff threshold.

Bluetooth drops mid-print job at partial charge

The wireless radio in mobile printers shares the 7.4V rail with the print head and motor. When battery charge drops below roughly 20%, the available voltage sags enough under combined load to starve the radio module. The device drops the Bluetooth or Wi-Fi connection before the battery reads as fully depleted on the indicator. If this happens consistently, keep the battery above 30% charge during active jobs — the radio requires a minimum stable supply to hold its pairing handshake through a full print sequence.