Diagral TF410X Replacement Battery 3.7V 90mAh

Diagral TF410X / DIAG44ACX — 3.7V Li-Polymer Replacement Battery

This is a 3.7V 90mAh Li-Polymer cell for the Diagral TF410X and DIAG44ACX wireless alarm transmitters. It replaces the original cell when the transmitter stops reporting to the panel or triggers a persistent low-battery alert. At 21.10 × 12.00 × 5.30mm, it matches the original footprint exactly.

• TF410X and DIAG44ACX compatibility: Both devices run the same 3.7V power rail and share an identical battery bay. The transmitter's onboard circuit monitors cell voltage directly, so swapping to this cell requires no configuration change on the panel side.
• Bench tested on actual hardware: We cycled this cell through charge and discharge on the bench. The protection circuit correctly flagged over-discharge at the low-voltage threshold and accepted a full charge without thermal event or capacity drop on the first cycle.
• Post-installation float period: Do not run a zone test or trigger a diagnostic scan immediately after fitting this cell. The panel reads cell voltage, not state of charge — allow 24 to 48 hours on float charge before testing, or the transmitter may report low battery during the test even with a new cell installed.

Why the TF410X still shows low battery hours after a new cell is fitted

The Diagral panel polls the transmitter at fixed intervals and reads raw cell voltage — not a percentage or a full-charge flag. A freshly installed Li-Polymer cell rests at around 3.6V to 3.7V open circuit, which sits close to the panel's low-battery threshold. The cell needs a full float charge cycle, typically 24 to 48 hours in the transmitter with the panel energised, before the resting voltage climbs above the warning threshold. Triggering the transmitter or running a test before that window closes will temporarily drop cell voltage and extend the low-battery alert.

Tamper fault appearing on the panel after the cell swap

If the panel logs a tamper fault immediately after battery replacement, the transmitter cover is almost always the cause. These housings use a spring-loaded tamper contact that must seat fully against the back plate — a small misalignment of 1 to 2mm is enough to hold the contact open. Remove the cover, reseat it with firm even pressure until you hear or feel the clip engage, then confirm the tamper fault clears from the panel event log. If the fault persists, check that no wiring or the cell itself is obstructing the back plate seating surface.