Ajax Hub 2 4G Backup Battery XK953580 3.7V 3000mAh

Ajax Hub 2 4G Series — 3.7V Li-Polymer Replacement Battery (XK953580)

This 3.7V, 3000mAh lithium-polymer cell replaces the internal backup battery in the Ajax Hub 2 4G and Hub 2 Plus control panels. It maintains alarm system operation during mains power outages. Capacity is 11.1Wh — match the OEM part number XK953580 before ordering.

• Hub 2 4G and Hub 2 Plus compatibility: Both panels share the same battery bay dimensions, connector pinout, and BMS charge profile. The 81.60 x 33.50 x 9.50mm cell fits both without modification, and the charge controller accepts the same float voltage from either board.
• Bench tested on actual hardware: We cycled this cell through the Ajax charge circuit and confirmed the BMS accepted the cell without fault codes. Charge current stabilised correctly and the panel cleared the low-battery event after a full float charge cycle.
• Post-installation conditioning: Do not run a zone diagnostic test immediately after fitting this cell. Allow 24–48 hours on float charge first. Running a test too early can cause the panel to report a low-battery fault even though the cell is functional — the BMS needs time to complete its charge acceptance cycle.

Alarm panel showing low battery hours after installing new cell

The Ajax Hub 2 4G does not simply read cell voltage to determine battery status. It runs a charge acceptance check through its internal BMS, and a freshly installed cell will not pass that check until it has completed a full float charge cycle. This typically takes 24–48 hours with mains power connected. If the panel flags low battery within the first day, that is the BMS still conditioning the cell — not a fault with the battery. Leave mains power on and check the panel app again after 48 hours.

Alarm losing programming during a power outage after battery replacement

If the panel loses its configuration during a mains failure shortly after a battery swap, the replacement cell had not yet been accepted by the charge controller. The Hub 2 4G requires the backup cell to reach a minimum state of charge before it will draw from it under load. A cell installed and tested within hours of fitting may show adequate open-circuit voltage but still fail under the panel's load draw. Allow a full 48-hour conditioning period on mains before testing backup operation — confirmed full charge shows 4.2V at the cell terminals.