Assa Abloy 550473 Automatic Door Replacement Battery 12V 1500mAh

Assa Abloy Slimdrive / Unislide Series — 12V Ni-MH Replacement Battery (1008425)

This is a 12V, 1500mAh Ni-MH replacement battery for the Assa Abloy automatic door operator backup system. It fits the 550473, 550475, Slimdrive, and Unislide series controllers. When mains power fails, this battery powers the door through its emergency open or close cycle to meet egress requirements.

• Slimdrive and Unislide backup circuit: These controllers share a common 12V backup rail and connector format across the 550473 and 550475 platforms. The BMS on each unit monitors float voltage and switches to battery the moment mains drops below threshold — same handshake across all listed models.
• Bench tested on actual hardware: We cycled this battery through simulated mains-fail events on a 550473 controller. The BMS accepted the cell pack without fault codes, completed the door cycle sequence, and returned to float charge without manual reset.
• Post-install verification: After fitting, manually trigger a power-fail test during a low-traffic period. Automatic door backup batteries must complete a full door cycle under load at installation — do not defer this test, as a depleted or unverified cell will not register as a fault until the next real outage.

Door controller losing programming after a power outage

The 550473 and 550475 store door parameters — open width, hold-open time, force sensitivity — in volatile RAM. That RAM requires the backup battery to hold its state when mains is lost. A depleted or dead backup battery means the controller writes nothing to non-volatile memory during the outage, and the door reverts to factory defaults on restart. If your door is resetting its travel limits or ignoring programmed obstacle settings after every power cut, the backup battery is the first component to check. Measure terminal voltage before fitting a replacement — a healthy Ni-MH pack at rest reads between 13.0V and 13.8V across the terminals.

Backup battery not activating when mains power drops

If the door stalls or loses power entirely during a mains failure rather than switching to battery, the backup circuit is not engaging. The most common cause is a deeply discharged cell pack that has dropped below the controller's minimum switchover voltage — the BMS will not engage a battery it reads as unsafe. A secondary cause is a corroded or poorly seated connector, which is common on door operators in high-humidity or outdoor-adjacent locations. Remove the battery, clean both contacts with isopropyl alcohol, and refit firmly. If voltage at the connector reads below 10V, the pack needs replacement — recharging a pack this far down is not reliable on this chemistry.