When the heartbeat stops, the station stands still.

A charging station holds a permanent connection to its backend. That connection can fail silently. A router dies, a fuse trips, the mobile network drops out. On the station itself every light stays on, and the portal shows it exactly as before.

So the station speaks up by itself. At a fixed interval it sends a short message: I am still here. A few minutes is the usual setting. The message is a handful of characters and gets through on the thinnest mobile link. Once it fails to arrive, the backend knows before the first driver pulls up.

Station and backend agree the interval when the station registers. The message itself carries no content. The reply carries the backend clock, and the station sets its own clock from it. A station whose clock has drifted files its sessions on the wrong day.

A missing heartbeat says the station is unreachable. It does not say why. In practice it is almost always the network connection, occasionally the power supply. A station without a connection accepts no card and reports no session.

An example: on a Friday evening the router in an underground car park fails. Without monitoring this surfaces on Monday, when the first tenant rings up. Twelve charge points stand idle until then. With monitoring the fault appears on the overview at 19:12 on Friday.

You hear about a fault before your users do. A call to the caretaker replaces a complaint. A station standing silent for days charges nobody and bills nothing.