The external battery adapter must be provided with a battery and put into immediate operation! This is absolutely necessary to support the internal battery of the HSM, even if the Hardware Appliance has not yet been put into operation or has been switched off again!

The Hardware Appliance is supplied with an external connector to plug-in a so-called battery adapter. Use this to buffer the internal HSM battery and extend its lifetime when the Hardware Appliance is switched off. This is useful, for example, when a Hardware Appliance is operated as an offline (root) CA:

The adapter supports standard 6LR61/9V batteries:

Insert the battery into the metal clip of the battery adapter. Use the connector on the back of the Hardware Appliance to connect it:

External Battery Adapter mounted on Hardware Version 2

External Battery Adapter mounted on Hardware Version 4

After up to 10 minutes, the external battery - Ext. battery - is displayed with status and voltage in the Hardware section of the Status page in WebConf.
The screenshot below shows that the battery is low and needs to be replaced.

This is how the displayed status would look with a good battery:

The external battery adapter contains active electronics (a voltage regulator) to convert the voltage of the 9 V battery to (IIRC) about 3.6 V (as shown in the screenshot), which the HSM needs from the external battery.