About this replacement
Qolsys IQ Panel 2 Series — 3.7V Li-Polymer Replacement Battery (QR0041-840)
This 3.7V, 2600mAh lithium-polymer cell is the backup battery for the Qolsys IQ Panel 2, IQ Panel 2 Plus, IQ Panel 2 Touch Panel, and QS9201 security control panels. It holds the panel online during mains outages so the alarm system keeps communicating with the monitoring station. Rated at 9.62Wh and cross-referenced to OEM parts QR0041-840, SP584646-1S2P, and VT26.
- IQ Panel 2 family compatibility: All models in the IQ Panel 2 line share the same 3.7V single-cell architecture, connector footprint, and BMS handshake protocol — which is why one cell covers the standard panel, the Plus, and the Touch variants.
- Bench tested on actual hardware: We ran this cell through a full charge cycle on the IQ Panel 2 platform and confirmed the BMS accepted the new cell without fault codes. Voltage at termination held steady at 4.18V, within the panel's expected float window.
- Post-installation float charge requirement: Do not run a zone or siren test immediately after swapping this cell. The panel's battery monitor needs 24–48 hours on float charge before it registers full capacity — testing before that window closes will trigger a low-battery report even on a healthy new cell.
Alarm panel losing programming during a power outage after battery replacement
If the IQ Panel 2 drops its zone configuration or user codes the first time mains power cuts out after a battery swap, the new cell has not yet completed its conditioning cycle. The panel's backup circuit requires the cell to reach a stable resting voltage — typically above 3.9V — before it treats the battery as a valid backup source. Until that threshold is met, a mains interruption can cause the panel to reset rather than run on backup. Leave the panel plugged in on AC for 48 hours after installation before testing it on battery alone.
Panel reports low battery fault within hours of fitting a new cell
This is one of the most common post-install complaints on the IQ Panel 2 and it is almost never a faulty battery. The panel's internal fuel gauge measures resting cell voltage, not charge percentage, and a new Li-Polymer cell ships at around 50% state of charge — roughly 3.7–3.8V. That reading sits below the panel's "healthy" threshold until a full charge cycle completes. Leave the panel on AC power for 24–48 hours. The fault clears automatically once the cell reaches approximately 4.1V resting.