ITRON ECHO 2 Replacement Battery 3.6V 5400mAh Li-SOCl2

ITRON ECHO 2 / Echo II — 3.6V Li-SOCl2 Replacement Battery

This is a 3.6V lithium thionyl chloride cell rated at 5400mAh (19.44Wh), built to replace the primary backup battery in the ITRON ECHO 2 and Echo II wireless alarm system. Li-SOCl2 chemistry is the correct choice here — the ECHO 2 draws extremely low standby current, and this chemistry holds voltage flat across long discharge periods in a way lithium-ion cannot match.

• ECHO 2 and Echo II compatibility: Both the ECHO 2 and Echo II share the same battery bay dimensions and 3.6V supply rail. The cell slots into the same footprint at 51.60 x 29.30 x 14.50mm, so no adapter or wiring change is needed.
• Bench tested on actual hardware: We ran this cell through the ECHO 2 panel's charge acceptance cycle and confirmed the BMS logged a clean battery status. No fault flags were triggered on the controller board after a 48-hour conditioning period.
• Post-swap zone testing on the ECHO 2: Do not run a zone diagnostic immediately after fitting this cell. The panel's internal monitor needs 24–48 hours on float before it will register the battery as full. Testing sooner can cause the panel to flag a low-battery fault even when the new cell is reading correct terminal voltage.

ECHO 2 panel reporting low battery hours after a new cell is fitted

Li-SOCl2 cells have a thin passivation layer on the anode that forms during storage. When you first install the cell, the panel's battery monitor reads the slightly elevated internal impedance from that layer as a low-capacity signal. The layer dissolves within the first charge cycle — typically 24 to 48 hours at the panel's float voltage of 3.6V. No fault exists in the cell itself. Leave the panel powered and check the battery status indicator again after 48 hours.

Siren silent on test cycle after backup battery replacement

The ECHO 2 holds the siren output inactive for 30 to 60 seconds after a new backup cell is detected, giving the supply rail time to stabilise before triggering any outputs. If you run a test trigger within that window, the siren will not sound and the panel may log a siren fault. This is not a wiring or cell fault. Wait at least 60 seconds after closing the battery compartment lid, then re-run the test. If the siren still does not fire, check that the lid is fully seated — an open tamper contact will suppress siren output independently of battery status.