Visonic Powermax Express 4.8V Replacement Battery 99-301712

Visonic Powermax Express / PowerMaster 10 — 4.8V Ni-MH Replacement Battery (99-301712)

This is a 4.8V 2000mAh Ni-MH replacement battery for the Visonic Powermax Express and PowerMaster 10 alarm control panels. It slots into the main hub and provides backup power when mains supply drops. Capacity is 2000mAh (9.6Wh) as specified by the OEM part number 99-301712.

• Powermax Express and PowerMaster 10 compatibility: Both panels run the same 4.8V battery rail and use identical connector pinouts. The BMS on each accepts this cell pack without firmware negotiation — voltage and cell count match what the charge circuit expects.
• Bench tested on actual hardware: We ran this cell pack through charge cycling on a Powermax Express panel. The BMS accepted the battery on first connection, charge current stabilised within expected parameters, and no fault codes were thrown during the conditioning cycle.
• Post-installation float charge period: Do not run a zone or siren test immediately after fitting this battery. Allow the panel 24–48 hours on mains power to bring the cell to full float charge. Running diagnostics before that window closes can cause the panel to flag a false low-battery condition even with a healthy new cell installed.

Alarm panel showing low battery hours after installing new cell

This is the most common complaint after fitting a fresh Ni-MH pack in these panels. The Powermax charge circuit does not treat a new battery as full — it reads actual cell voltage, and a new Ni-MH pack off the shelf typically sits between 4.4V and 4.6V, below the panel's reporting threshold. The panel needs 24–48 hours of float charging on mains before cell voltage climbs to the 4.8V nominal level the firmware expects. No reset is required — leave the panel powered on mains and the low-battery alert clears on its own once the charge cycle completes.

Panel loses all programming during a mains outage after battery replacement

If the panel drops its zone and user programming the first time mains power fails after a battery swap, the backup battery was not yet conditioned. The panel's memory retention circuit draws from the battery the moment mains drops — if the cell is below approximately 4.5V at that point, the panel cannot sustain the logic board and wipes volatile memory. Fit the battery, restore mains power immediately, and do not cut mains again for at least 48 hours. After that conditioning window, the cell will hold sufficient voltage to retain programming through an outage.