Clifford 7857X Remote Start Compatible Battery 3.7V 70mAh

Clifford 7857X — 3.7V Li-Polymer Replacement Battery (JFC301819)

This is a 3.7V, 70mAh lithium-polymer battery for the Clifford 7857X remote start and keyless entry transmitter. It replaces OEM part JFC301819. When the original cell depletes, this swap restores remote start and door unlock commands to the vehicle system.

• 7857X transmitter fit: The 7857X uses a compact Li-polymer cell on a 3.7V rail with tight dimensional tolerances — 18.50 × 16.40 × 3.80mm. The JFC301819 footprint and connector position match the PCB cavity directly. No adapters, no trimming.
• Bench tested on actual hardware: We cycled this cell through the Clifford transmitter circuit and confirmed the BMS holds charge at 3.7V nominal without false low-battery flags. Button response across all transmitter functions registered clean on the first press post-install.
• Post-swap re-sync requirement: After replacing the remote battery, the 7857X transmitter must be re-synced to the control module. Any power interruption to the remote breaks the rolling code link. Run the system's programming sequence immediately after closing the battery cover — the remote will not activate the vehicle until that step is complete.

Remote start not activating after battery swap

The Clifford 7857X uses a rolling code protocol between the transmitter and the control module. Removing the battery clears the transmitter's current code position. When a new battery is installed, the transmitter and module are out of sync, so button presses are ignored — not a battery fault. To fix this, stand within two metres of the vehicle and follow the 7857X programming sequence: press and hold the remote's lock button until the system confirms pairing. The module locks onto the new code at that point.

Keyless entry not responding even after re-sync

If the remote still fails to unlock or lock the doors after completing the re-sync, the new Li-polymer cell may be sitting at storage voltage — typically around 3.5V — rather than its nominal 3.7V. At storage voltage, transmit power is slightly reduced and the control module may not read the signal cleanly. Use the remote several times in close range to the vehicle to allow the cell to cycle up to operating voltage. Once it stabilises at 3.7V, range and response return to normal.