About this replacement
Teltonika TM250 — 3.8V Li-Polymer Replacement Battery (ZN703035)
This 3.8V, 950mAh Li-Polymer battery replaces the OEM ZN703035 pack in the Teltonika TM250 personal and asset GPS tracker. It fits the compact TM250 unit used in surveying, field testing, and equipment monitoring workflows. Install it to restore GPS positioning and data transmission to a tracker with a depleted or failed original cell.
- TM250 platform fit: The TM250 uses a single-cell Li-Polymer pack at 3.8V nominal, matched to the device's low-power GPS and cellular transmission circuit. This replacement matches that voltage rail and the physical footprint at 37.90 × 29.00 × 7.20mm, so the connector and cell seating align correctly.
- Bench tested on actual hardware: We cycled this pack through GPS acquisition and cellular uplink loads on the TM250 bench unit. The BMS handled the current spike at cellular transmission without tripping, and the protection circuit held within the expected voltage window across discharge.
- Post-install tracker sync: After fitting this battery, allow the TM250 to complete a full GPS fix and data sync cycle before deploying it in the field. The device recalibrates its power state monitoring during this first active session — skipping it can cause premature low-battery alerts during early logging sessions.
BMS lockout after the TM250 sat unused in a case for months
Li-Polymer cells self-discharge slowly during storage. If the TM250 was left unpowered for several months, the cell voltage can drop below the BMS recovery threshold — typically around 2.5V for a 3.8V nominal cell. At that point the protection circuit locks out charging entirely as a safety measure, and the device will not respond to a charger. Connect the TM250 to a USB power source for 15–20 minutes to allow the BMS to register the incoming voltage and exit lockout before attempting a full charge cycle.
TM250 shuts down mid-transmission during active GPS logging
The TM250 draws a higher current burst when the cellular modem fires a data uplink, especially when signal is weak and the radio increases transmit power. A worn or marginal cell cannot sustain that instantaneous load, and the voltage sags enough to trigger the BMS undervoltage cutoff — even when the displayed charge level appears adequate. This is a load-response failure, not a capacity failure. Replacing the cell restores the voltage headroom needed to handle those transmission spikes without dropout.