The battery in the HSM has an expected lifespan of approximately 10 years. It is gated out whenever the HSM is powered on so the only drain on it is due to its own physical deterioration.

When power is not connected, it's life expectancy remains this long due to the miniscule current requirements in use.

It is recommended that all HSM's be part of a maintenance schedule and the battery replaced on a rolling basis after about 7 years.

The fault LED will flash if the battery is low, however it will flash for other reasons and therefore this is not a totally satisfactory indication that the battery is good.

To properly check this, the HSM should be taken offline and the DT console command run. One of the indications is the battery condition. This should say 'OK'.

Ensure power is connected and switched on when this check is carried out. If power is disconnected and the battery is low, the LMK will be lost and the HSM configurations returned to default.

Finally, ensure that all LMK components, and the HSM's configurations are available so that, should a problem occur, recovery procedures can be carried out.