About this replacement
DoorLock DL-31 / HTL18 — 9V Alkaline Replacement Battery
This is a 9V alkaline battery rated at 2300mAh (20.7Wh), sized for the DoorLock DL-31 and HTL18 electronic door locks. It powers the keypad controller, motor driver, and wireless module inside both units. One cell handles the full logic and actuation stack on these locks.
- DL-31 and HTL18 compatibility: Both models run a shared 9V single-cell architecture. The same voltage rail drives the keypad input circuit, the Bluetooth radio, and the motorised bolt. One battery spec covers both locks.
- Bench tested on actual hardware: We ran this cell through the DL-31's power-on sequence. The BMS accepted the battery without flagging a low-voltage alert, and the motorised bolt cycled cleanly through lock and unlock without a mid-stroke cutoff.
- Post-swap access check: After fitting the battery, test every access method — keypad, Bluetooth, and any keycard — before you close the door. Some firmware handshakes only complete after a full power cycle, and a lock that hasn't finished that sequence won't accept all credential types.
Why the DL-31 stops responding after a battery swap
When power is interrupted, the DL-31's microcontroller loses its active state and requires a clean reboot sequence to reinitialise. Simply inserting the new battery isn't always enough — the controller needs to complete its startup routine before it accepts input. If the lock is unresponsive after the swap, remove the battery, wait ten seconds, and reinsert it. That clears the register state and lets the firmware boot from scratch.
Low battery warning showing immediately after fitting a new cell
The DL-31 reads battery state by measuring open-circuit voltage at startup. A fresh 9V alkaline should read 9.0–9.6V at rest — anything below 8.4V will trigger the low-battery indicator immediately. This happens when a cell has been sitting in storage and has lost surface charge, or when a non-alkaline 9V is fitted. Verify the installed cell reads at least 8.8V with a multimeter before closing the battery compartment.