About this replacement
Grothe FA30 Series — 4.8V Ni-MH Replacement Battery (39180)
This is a 4.8V 2000mAh Ni-MH cell built to replace the backup battery in Grothe FA30 wireless door chime systems. It fits the FA30, FA30-AZ, and FA30-RP10 receivers and transmitters. Voltage and pack dimensions match the original Grothe OEM spec (39180).
- FA30, FA30-AZ, FA30-RP10 compatibility: All three variants share the same 4.8V four-cell Ni-MH configuration, connector pinout, and physical envelope (50.50 × 28.60 × 28.50mm). The chime controller board draws charge current from a fixed 4.8V rail — swapping to any other voltage causes the onboard charge circuit to behave incorrectly.
- Bench tested on actual hardware: We cycled this cell through the FA30 charge circuit and confirmed the BMS accepted the pack without fault flags. The receiver completed a full float charge cycle and held resting voltage within the expected Ni-MH window.
- Float charge conditioning after install: Do not run a zone or chime test immediately after fitting this cell. The FA30 charge circuit needs 24–48 hours to bring a new Ni-MH pack to full float charge. Running a diagnostic test before that window closes will cause the panel to report a low battery condition even on a healthy new cell.
FA30 panel showing low battery hours after installing a new cell
The FA30's charge controller samples cell voltage against a fixed threshold to decide whether to raise a low battery flag. A fresh Ni-MH pack ships at partial charge — typically 30–50% — so the resting voltage sits below that threshold on day one. The panel isn't faulty and the new cell isn't faulty either. Leave the system on mains power for a full 48 hours before checking battery status. After that conditioning window, the flag should clear and the display should show a stable 4.8V across the pack.
Chime not sounding on the first test after a battery swap
The FA30 receiver holds the alert output in a suppressed state for 30–60 seconds after a power cycle or battery replacement. This is intentional — the firmware waits for charge stabilisation before enabling the siren output, so a test pressed immediately after fitting the new cell will produce no sound. Wait at least 60 seconds after closing the battery compartment and restoring power before pressing the doorbell transmitter. If the chime still does not sound after that delay, check that the compartment lid is fully seated, as an open tamper contact on the FA30-AZ and FA30-RP10 will also mute the alert output.