Daitem SH511AX Replacement Battery 3.7V 1500mAh RXU03X

Daitem SH511AX / SH512AX Series — 3.7V Li-ion Replacement Battery (RXU03X)

This is a 3.7V 1500mAh Li-ion replacement cell for Daitem wireless alarm components, including sensors and detectors across the SH511AX, SH512AX, SH513AX, and SH514AX series, plus a further 16 compatible models. It cross-references OEM part numbers RXU03X, F000230, BATXU03, and BATLi30, among others. Physical dimensions are 52.00 × 20.00 × 18.50mm — verify against the original cell before fitting.

• SH511AX–SH514AX series compatibility: These models share the same 3.7V single-cell architecture, connector pinout, and BMS handshake protocol. The same cell fits across the range because Daitem standardised the power interface on this generation of wireless detectors.
• Bench tested on actual hardware: We cycled this cell through charge and discharge on a Daitem-compatible test rig. The BMS accepted the cell without fault codes, held the float charge correctly, and reported accurate state-of-charge to the panel after a 48-hour conditioning period.
• Post-installation float charge requirement: Do not run a zone diagnostic test immediately after fitting this cell. Allow 24–48 hours on float charge first. Running a test before the cell reaches full float charge can cause the panel to log a spurious low-battery fault, which may persist until the next poll cycle.

Alarm panel showing low battery hours after installing the new cell

Daitem panels do not simply read cell voltage — they poll state-of-charge through the BMS at timed intervals. A freshly fitted cell that hasn't completed its first full float charge will report below the panel's acceptance threshold. This triggers a low-battery event even though the cell is functional and not faulty. Leave the system powered and armed for 24–48 hours before drawing any conclusions. If the fault clears after that window, the cell is fine — no further action needed.

Alarm losing zone programming after a mains power outage following battery swap

The backup cell must be fully conditioned before it can sustain panel memory through a mains interruption. If a power outage occurs within the first 48 hours after fitting, the cell may not yet hold enough charge to keep the panel logic alive, causing zone data and settings to reset. This is a conditioning window issue, not a cell fault. After the full 48-hour float charge period, the cell will hold sufficient charge to back up panel memory through a typical outage — confirm by checking the panel reads a healthy battery status at 3.6V or above before the next planned power test.