Low Battery

Low Battery

Every battery Device Sentinel finds is watched by default. New devices with batteries are picked up automatically the moment they appear in your registry; there is nothing to register or manually configure per device.

This screen allows you to define what counts as a low battery and configure exclusions for devices whose battery levels you do not want reported.

Discovery and Election

Each device gets one elected battery entity. When a device reports both a percentage battery and a binary low-battery flag, the percentage is always elected because it tells the integration how low the battery is, rather than just that it is low. If that percentage entity ever disappears, the flag entity is elected in its place automatically.

Battery judgment belongs to the device itself, not the specific entity. This election process means the judged entity can change over a device's life, which is why there is no per-entity exclude list on this screen: a device-level exclusion cannot be bypassed just because the underlying entity changed.

How a Battery Is Judged

A battery is flagged when its level is at or below your defined threshold.

• The threshold: The default is 20 percent, set on this screen. A dashboard slider for it existed until 0.11.10 and was removed: it was the only control on the device page, it duplicated this screen, and the second battery setting beside it never had one.
• The margin: A flagged battery only clears once it climbs 2 points above the threshold. This margin exists because battery readings frequently rebound: a cell under load dips, rests, and recovers a point or two. Without this margin, a battery sitting exactly at the line would flap in and out of the report. With it, a clear is a genuine recovery.
• Persistence: The exact moment a battery first crosses the threshold is saved immediately and kept across restarts, so a battery that has been low since Tuesday stays true through a reboot.

Battery watching is its own independent detection family. It reads levels rather than reporting rhythms, meaning a chatty device and a once-a-day device are judged identically. A battery crossing the threshold in either direction immediately joins or leaves the problem list and fires notifications, subject to your standard settle periods and quiet hours.

The Second Question: Which Are About To Be Low

The threshold answers which cells are low. It cannot answer which are about to be, and those are rarely the same devices.

On the development fleet one morning a soil sensor read 82 percent and a door sensor 24 percent. The percentages say the soil sensor is healthier. It is not: the door sensor had a week left and the soil sensor had two months, because one was falling and the other was drifting.

Days Till Empty is the setting for that, and it sits on this screen beside the threshold. A cell projected to reach empty inside this many days is flagged, so it reaches your problem list, your daily brief and your phone the same way a low battery does. The range is 7 to 30 days, defaulting to 30: under a week is too late to act on, and past a month a projection is guesswork.

A flagged cell reads "battery empty in about 2 weeks". It says the time in words rather than a count of days on purpose, because the projection moves as the cell reports; The Battery Report explains why and shows the whole picture.

Two things follow that are worth knowing. A cell that is not moving is never flagged here, so a healthy fleet stays quiet. And a cell already below the threshold is not flagged twice: when both apply, one item reads "battery 16%, empty in about 2 weeks".

Where It Is Visible

You will see low batteries on the problem list (for example, "Soil Irrigation: battery 0%"), where they can be acknowledged to silence notifications. They also appear in your daily brief. For a deeper look, The Battery Report is the page written for this, and the device_telemetry report records battery levels day by day, so a cell's drain over recent weeks is visible in one row.

The Excludes

Excluding a battery on this screen stops battery reports for that device only. Everything else about the device, like whether it has frozen or fallen offline, stays watched. If you want to drop a device from all reporting entirely, use the Global Exclusions screen instead.

There are three exclusion lists, running from broad to narrow. They interact exactly like the global lists: if you exclude at a higher level and save, everything it covers disappears from the narrower lists below. Remember the dropped-not-parked rule: if you later undo a broad exclusion, you will need to re-pick any narrow items you still want excluded.

Integrations

One tick covers every battery that integration owns, present and future. The most common use for this is ticking mobile_app, which instantly covers every phone and tablet at once, including ones you have not bought yet, keeping their daily charging cycles from creating battery noise.

Labels

Any device carrying one of these labels stops being reported for a low battery. You can set the label directly on the device's own page in Home Assistant, and the exclusion applies without needing to open this dialog.

Devices

Every device listed here has a tracked battery, and its elected battery entity is shown alongside it, so this picker doubles as an inventory of exactly what is being battery-watched. Checked devices are excluded from battery reporting. When excluded here, their STATUS column in the telemetry report reads "Excluded (BAT)".