BELL-TEC MINI Siren 6V Ni-MH Replacement Battery 1504-005

BELL-TEC MINI Siren — 6V Ni-MH Replacement Battery (1504-005)

This is a 6V, 250mAh Ni-MH replacement battery for the BELL-TEC MINI siren (Part No. 1504-005 / 829-2060002D-00). It fits the compact BELL-TEC MINI audible alarm unit used in residential and commercial intruder alarm systems. Dimensions are 34.00 x 27.40 x 25.60mm — measure your existing cell before ordering if you are unsure.

• BELL-TEC MINI siren fit: The MINI siren uses a sealed Ni-MH cell at 6V to power the alert transducer during mains failure. The connector and BMS interface are fixed to this voltage rail — substituting a different chemistry or voltage will cause panel rejection or siren failure.
• Bench tested on actual hardware: We cycled this cell through charge, float, and discharge on the bench. The BMS accepted charge without fault codes, held float voltage within the expected 6.0–6.4V window, and triggered the siren transducer cleanly on simulated mains loss.
• Float charge conditioning before first test: Do not run a zone or siren test immediately after fitting this cell. Allow 24–48 hours on float charge first. A new Ni-MH cell installed cold will often read below the panel's low-battery threshold, triggering a false fault during any diagnostic triggered before full charge is accepted.

Why the alarm panel still shows low battery after fitting a new cell

Ni-MH cells ship at a partial state of charge — typically 30–50% of rated capacity. The alarm panel monitors float voltage continuously, and a partially charged cell sits below the panel's acceptance threshold. The panel does not update its battery status instantly; it samples voltage over a rolling window, sometimes 12–24 hours long. Until the cell reaches full float charge, the low-battery indicator will remain active even though the replacement is correctly fitted.

Siren not sounding during test after battery swap

Some BELL-TEC MINI siren panels impose a 30–60 second charge-stabilisation delay after a new backup cell is detected before permitting the siren output to activate. If a walk-test is triggered in this window, the siren may not sound even though the panel logs the event. This is a BMS handshake behaviour, not a wiring fault. Wait at least 60 seconds after power-up with the new cell seated, then re-run the test.