Teltonika LP621230 FMB Tracker Replacement Battery 3.7V 150mAh

Teltonika FMB Tracker Series — 3.7V Li-Polymer Replacement Battery (LP621230)

This is a 3.7V, 150mAh Li-Polymer cell replacement for the Teltonika FMB Tracker, FMA1yx, and FMB1yx series GPS tracking devices. The LP621230 form factor measures 31.00 × 11.60 × 5.00mm and slots directly into the tracker housing. Continuous GPS polling and cellular transmission cycles drain the original cell faster than most users expect.

• FMA1yx and FMB1yx platform fit: Both device families share the LP621230 footprint and the same 3.7V supply rail to the cellular modem and GPS module. The connector pinout and BMS handshake are consistent across the range, so one cell covers the full cluster.
• Bench tested on actual hardware: We ran this cell through power-on initialisation, GPS lock acquisition, and a sustained GPRS transmission cycle. The BMS held voltage within the expected window under combined modem and GPS draw, with no premature cutoff events recorded.
• Post-install initialisation on the FMB Tracker: After fitting the new cell, send the device a configuration command via SMS or Teltonika Configurator to trigger a full parameter reload. The tracker maps battery state during this initialisation cycle — skipping it causes the device to report false low-battery alerts on the first active logging session.

BMS cutoff when the cellular modem fires its first transmission burst

The FMB Tracker's GPRS modem draws a sharp current spike at the start of each transmission burst — this is well above the steady-state GPS polling current. On a deeply discharged or newly installed cell sitting below 3.5V, the BMS can interpret that spike as an overcurrent event and cut the output. The device appears to power off cleanly, but the cause is the BMS tripping, not a firmware fault. Charge the cell to at least 3.8V before first use and confirm the modem initialises without cutoff before field deployment.

Tracker powers on and acquires GPS lock, then drops offline mid-logging session

This happens when sustained dual-load draw — GPS module active plus cellular reporting at short intervals — pulls cell voltage below the BMS low-voltage threshold faster than the firmware anticipates. It is not a GPS or SIM fault. The original cell shows this behaviour first as interval creep in the log timestamps before full dropout occurs. Check the cell voltage under load with a multimeter at the battery terminals; anything sagging below 3.3V under the combined draw points to a cell that needs replacement.