About this replacement
ADT Command Secondary Color Touchscreen Keypad — 3.8V Li-Polymer Replacement Battery (P-504478)
This 3.8V, 2800mAh Li-Polymer cell replaces the internal backup battery in the ADT Command Secondary Color Touchscreen Keypad (OEM part P-504478). The keypad acts as a wireless secondary interface for arming, disarming, and accessing your ADT alarm system. Without a functioning cell, the keypad loses its backup power and can go offline during a mains outage.
- ADT Command Secondary Keypad fit: This cell matches the P-504478 voltage rail and physical footprint exactly. The keypad's onboard BMS communicates battery state to the main panel — wrong voltage or a mismatched connector interrupts that handshake and triggers a tamper or low-battery fault at the panel.
- Bench tested on actual hardware: We cycled this cell through charge and discharge on the bench. The BMS accepted charge cleanly, reported state-of-charge correctly to the panel after the float period, and held voltage within the keypad's operating window without tripping a fault condition.
- Post-installation float period: Do not run a zone or diagnostic test immediately after fitting this cell. Allow 24–48 hours on mains power so the battery reaches full float charge first. Testing before that window closes can cause the panel to report a low-battery fault even on a new cell.
Why the ADT Command panel still shows low battery after swapping the keypad cell
The ADT Command panel reads battery state through a BMS voltage threshold, not an instant voltage reading. A freshly installed Li-Polymer cell sits below the panel's "full" threshold until it completes its first full float charge cycle. The panel samples battery status on a timed poll, so it takes several polling cycles — often 12 to 24 hours — before the reported status updates. Leave the system on mains power for 48 hours after the swap, then check the panel status screen again.
Keypad goes blank or unresponsive during a power cut after battery replacement
If the keypad drops out the moment mains power fails, the replacement cell has not yet been accepted as the active backup source. This happens when the panel's BMS has not completed its conditioning cycle on the new cell. The panel will not switch to battery backup from an unconditioned cell to prevent an undervoltage fault mid-outage. Keep the system powered continuously for 48 hours after installation — after that, the panel treats the cell as a fully conditioned backup source at approximately 3.8V nominal.