Automate 7857A Remote Compatible Battery 3.7V 70mAh Li-Polymer

Automate 7857A — 3.7V Li-Polymer Replacement Battery (JFC301819)

This is a 3.7V 70mAh Li-Polymer cell for the Automate 7857A key fob. It fits the transmitter used for remote start, door lock, and keyless entry functions. Swap it when the fob stops triggering the vehicle or shows reduced response at close range.

• Automate 7857A fob platform: The 7857A transmitter runs on a single Li-Polymer cell at 3.7V nominal. The fob's internal circuit draws from this cell directly — there is no secondary regulation stage, so cell voltage tracks directly to transmit power and signal consistency.
• Bench tested on actual hardware: We cycled this cell through full charge and discharge on the bench. The protection circuit handled over-discharge cutoff cleanly and recovered to full charge voltage without BMS lockout.
• Re-sync after battery swap: After replacing the battery, re-sync the remote to the Automate control module. The 7857A system requires a programming sequence after any power interruption to the fob — without it, the transmitter will not activate the remote start or entry functions.

Remote start not activating after battery swap on the 7857A

Fitting a new cell does not automatically restore communication with the Automate control module. The 7857A uses a rolling code system that loses its position when the fob loses power. After the swap, the fob and module need to re-establish their code sequence through the system's programming sequence. Check the 7857A installation guide for the exact button combination — most Automate remotes require pressing a specific key sequence within range of the vehicle to complete re-pairing.

Fob range shorter than expected right after fitting the new cell

A fresh Li-Polymer cell ships at storage voltage — typically around 3.6V — not at full charge. At storage voltage, transmit power is slightly below peak, which can cut effective range. Charge the fob fully before the first use if your charger supports it, or allow two to three normal use cycles for the cell to reach operating voltage. If range stays short after that, confirm the replacement re-sync completed correctly, as an incomplete pairing can also suppress signal output.