About this replacement
Ajax Hub Series — 3.7V Li-Polymer Replacement Battery (XK953562)
This is a 3.7V, 2100mAh Li-Polymer cell that replaces the internal backup battery in Ajax Hub, Hub 2, Hub 2 Plus, and AJ-HUB-W/B control panels. The Hub is the central processor of Ajax alarm systems — it manages all wireless sensor communication and maintains alarm state during mains power outages. When the original cell degrades, backup power drops and the panel begins reporting low battery warnings.
- Hub and Hub 2 series compatibility: All four panel variants share the same 3.7V Li-Polymer cell, connector pinout, and BMS handshake protocol. The XK953562 part number covers the full range without any hardware modification.
- Bench tested on actual hardware: We ran this cell in a Hub 2 Plus on the bench. The BMS accepted the cell immediately, entered float charge within the expected window, and cleared the low-battery flag after the conditioning period completed.
- Post-install zone testing: Do not run a zone diagnostic immediately after fitting this cell. The panel BMS requires 24–48 hours at float charge before it reports an accurate battery state. Running a test before that window closes will trigger a false low-battery alert in the Ajax app.
Alarm panel showing low battery hours after installing a new cell
Ajax panels do not read battery state from raw voltage alone — the BMS monitors charge acceptance over a conditioning window before updating the reported status. A freshly installed cell will often sit at or near 3.7V but the panel still flags low battery because the conditioning cycle has not completed. This is not a fault with the cell. Leave the panel on mains power for 48 hours, then check the Ajax app — the alert will clear once float charge is confirmed.
Alarm losing stored programming during a mains outage after battery swap
If the panel drops its configuration during a power cut shortly after a battery replacement, the new cell had not yet been accepted by the BMS as a valid backup source. The panel treats an unconfirmed cell as absent and cannot sustain memory or communication. Re-seat the battery, restore mains power, and allow a full 48-hour charge cycle before testing backup operation. After that window, the BMS will hold the cell in reserve and programming will survive outages normally.