Besam Unislide 12V Replacement Battery 45A020BA00004

Besam Unislide / Unislide II Sliding Door — 12V Ni-MH Replacement Battery (45A020BA00004)

This 12V 1500mAh Ni-MH battery replaces the backup power cell in Besam Unislide and Unislide II automatic sliding door operators, as well as EXU1 and EXU3 units. It holds the backup circuit charged so the door can complete full open and close cycles during a mains failure. Capacity is 18Wh at 12V nominal.

• Unislide and EXU platform fit: The Unislide, Unislide II, EXU1, and EXU3 controllers share the same 12V backup rail and battery bay connector. All use OEM part 45A020BA00004 — also cross-referenced as 33550475, 550473, 550475, and MFH9001 depending on the supply chain source.
• Bench tested on actual hardware: We cycled this cell through the Besam backup circuit under a full motor load. The BMS accepted charge without fault flags, and the battery sustained the voltage rail through multiple complete door cycles without tripping the low-voltage cutoff.
• Power-fail verification at installation: After fitting the battery, manually interrupt mains power during a low-traffic period and let the controller run through at least one full open-and-close cycle. Automatic door backup systems must be load-tested at installation — a battery that reads charged on a multimeter can still fail to deliver peak current during motor start.

Door controller losing programming after a power outage

Besam Unislide controllers store door timing, obstacle sensitivity, and hold-open settings in volatile RAM. That RAM is kept alive by the backup battery during mains loss. When the backup battery is deeply discharged or has failed entirely, even a brief power interruption wipes those settings. If the door reverts to factory defaults after every outage, the battery is the first thing to check — not the controller board. A healthy battery at rest should read between 12.0V and 13.2V on a multimeter; anything below 11.5V means the cell can no longer hold the memory rail.

Battery backup not activating during mains failure

If the door goes dead the moment mains power drops, the backup circuit is not switching over — or the battery has insufficient charge to trigger it. The Besam backup circuit requires the battery to be above its activation threshold voltage before it will engage the transfer relay. A battery that has sat uncharged for months may read low enough that the controller ignores it entirely. Fit the new battery, allow 24 hours on charge with the controller powered, then run a mains-interrupt test to confirm the relay engages and the door completes a full cycle.