Indexa Repeater 9000FR Compatible Battery 4.8V 800mAh Ni-CD

Indexa Repeater 9000FR 35516 — 4.8V Ni-Cd Replacement Battery (3695887)

This 4.8V, 800mAh Ni-Cd cell replaces the OEM battery (part no. 3695887) inside the Indexa Repeater 9000FR 35516 wireless alarm repeater. The repeater extends signal range between sensors and the alarm panel — when its backup cell degrades, the unit can drop off the network during a mains fault. Dimensions are 57.00 × 50.50 × 14.40mm, matching the original housing exactly.

• Repeater 9000FR 35516 compatibility: This cell shares the same voltage rail and connector footprint as the original factory cell. The BMS on the repeater board expects a 4.8V Ni-Cd charge profile — substituting a Li-ion or NiMH cell at similar voltage will cause incorrect charge termination and premature failure.
• Bench tested on actual hardware: We ran this cell through charge acceptance on the repeater board. The BMS accepted full charge without fault flags. Discharge under simulated mains-loss conditions showed stable output through the expected backup window with no mid-cycle voltage collapse.
• Post-installation float period: Do not run a zone or signal test immediately after fitting this cell. The repeater panel requires 24–48 hours on float charge before it accepts the cell as fully conditioned. Testing before that window clears will trigger a low-battery report even on a healthy new cell.

Why the 9000FR 35516 drops off the network during a mains fault

The repeater relies entirely on its backup cell the moment mains power drops. A degraded Ni-Cd cell that reads acceptable on a static meter can still collapse under the load of active RF transmission. Ni-Cd cells lose capacity through crystalline dendrite buildup — voltage sags sharply under draw even when resting voltage appears normal. If the repeater is losing network sync during power cuts, the cell is the first thing to swap, not the antenna or panel firmware.

Panel reporting low battery fault 24 hours after fitting a new cell

A low-battery fault that persists a full day after installation usually means the cell has not yet reached float charge. The 9000FR board charges at a trickle rate — it can take up to 48 hours to fully condition a new Ni-Cd cell from a discharged state. Check that the repeater has uninterrupted mains power during this window. If the fault clears between 24 and 48 hours, the cell and board are both functioning correctly; if it persists past 48 hours, measure the cell terminal voltage — a healthy charged cell should sit at or above 5.0V under no load.