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:

Battery adapter

The adapter supports standard 6LR61/9V batteries:

Battery adapter with connected battery

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

Hardware Appliance with connected battery adapter

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:

WebConf: Battery status

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.