agtatec AG STG19 Replacement Battery 19.2V 2000mAh Ni-MH

agtatec AG STG19 / STM 21 / BAT 19 — 19.2V Ni-MH Replacement Battery (80100505)

This 19.2V, 2000mAh Ni-MH battery replaces the agtatec AG part number 80100505 backup battery used in the STG19, STM 21, and BAT 19 automatic door operators. It powers the motor drive and control electronics during mains failure, keeping the door operational through a full open-and-close cycle. Capacity matches the original at 38.4Wh — no modifications needed to the controller.

• STG19, STM 21, and BAT 19 compatibility: All three models share the same 19.2V battery bay, connector pinout, and BMS charge profile. The controller's charge circuit recognises Ni-MH chemistry and applies the correct delta-V termination — no compatibility workaround required.
• Bench tested on actual hardware: We ran this battery through a simulated mains-fail cycle and monitored the BMS under motor-start load. The cell stack held voltage through the inrush spike at door activation and the BMS did not trip at any point during the full open-and-close sequence.
• Post-install power-fail verification: After fitting this battery, manually trigger a mains-fail test during a low-traffic period before relying on it. Automatic door backup batteries must complete a full door cycle under real motor load — a resting voltage check alone does not confirm the battery can handle the current draw at activation.

Why the STG19 door stalls mid-cycle on battery backup

The STG19 motor draws its highest current at the start of the open cycle — the inrush load at activation is significantly higher than the steady running current. A degraded Ni-MH pack loses cell voltage under that initial spike, which the controller reads as an undervoltage fault and halts the sequence. The door then sits partially open until mains power restores. A new battery at full charge resolves this — the cell stack needs to hold above 17V through the inrush event to clear the fault threshold.

Door controller losing stored settings after a power outage

The STG19 and STM 21 store door-profile settings — travel limits, speed curves, and obstacle-detection thresholds — in volatile RAM that requires continuous low-current supply from the backup battery to persist. When the backup battery drops below its retention threshold, a mains outage wipes those settings. The controller then defaults to factory parameters, which typically means the door will not travel its correct full distance. Fitting a charged replacement and allowing a full 24-hour charge cycle before the next power event prevents the settings loss.