About this replacement
TEKNIM 720WR Siren — 6V Ni-MH Replacement Battery (0703-033)
This is a 6V 600mAh Ni-MH replacement cell for the TEKNIM 720WR wireless siren. It fits directly in place of the original backup battery inside the siren housing. When the existing cell can no longer hold charge, this unit restores the siren's ability to sound during a mains power failure.
- 720WR siren fit: The 720WR uses a 6V Ni-MH cell on a dedicated charge rail separate from the main alarm bus. The replacement matches the OEM voltage, chemistry, and connector polarity so the panel's charge circuit continues operating without modification.
- Bench tested on actual hardware: We cycled this cell through charge and discharge on a 720WR-class siren board. The BMS accepted the cell without fault flags, and the charge circuit held the cell at correct float voltage throughout the test.
- Post-installation charge window: Do not run a zone or siren test immediately after fitting this cell. Allow 24–48 hours on float charge first. Running a test on a partially charged cell can cause the panel to log a low battery fault that clears only after a full charge cycle completes.
Why the 720WR panel reports low battery hours after a new cell is fitted
The 720WR alarm panel monitors battery voltage against a fixed threshold, typically around 5.8V. A new Ni-MH cell ships in a partial state of charge — often below that threshold — so the panel flags low battery straight away. This is not a fault with the cell. The panel needs to see the cell hold at or above threshold voltage for a sustained period before it clears the alert. Leave the system on mains power for 24–48 hours and the flag will clear once the cell reaches full float charge.
Siren does not sound during a test cycle after battery swap
Some 720WR panels impose a brief inhibit window on the siren output after a battery change is detected. This is a built-in protection to prevent the siren from drawing heavy current before the backup cell has stabilised. The delay is typically 30–60 seconds from power-on. If the siren still does not trigger after that window, check that the siren lid is fully closed and latched — an open tamper contact on the siren housing will suppress the output independently of battery state.