Can a phone last all night as a baby monitor? The honest battery guide

BOBlagovest Ouglechov·September 1, 2026·3 min read

The most common worry when an old phone becomes a baby monitor: "Will it even make it to morning?" The short answer: yes — if the app takes the battery seriously. The long answer is worth reading, because it explains why some setups die at 3 a.m.

What actually drains the battery

Three things cost power during a baby-monitor night, in this order:

1. The camera. The sensor plus video encoding are by far the biggest consumers. A "muted" video stream with the camera secretly still running saves almost nothing.
2. The screen. A bright display all night can empty a battery on its own.
3. The radio. Wi-Fi streaming costs something — but far less than camera and screen.

The reference numbers we plan with at Pevu: audio-only streaming runs at roughly 5% battery per hour, video on an Android device at roughly 15%. An eight-hour night on audio-only works even without a plug — on video it doesn't. Hence:

The most important rule: plug in the nursery device. Not because it would certainly die otherwise — but so you never have to do the math at midnight.

How Pevu plans the night

We built Pevu to treat your battery the way you do: as something that still needs to be there in the morning.

• Audio-only as a real mode. Choose "audio only" and the camera permission is never even requested. In eco mode the camera is truly shut down, not just muted — the difference is many percent per hour.
• Peek instead of permanent video. Want a quick look? One tap turns the camera on for 30 seconds, then it's off again.
• Audio before video. When Wi-Fi gets weak, Pevu sacrifices the picture first and the sound never. A baby monitor that goes quiet on a bad connection would be the wrong baby monitor.
• Plain language instead of percentages. The parent unit doesn't just show "43%" — it tells you what that means: "not charging — about 3 hours left." Below 20% it warns you and forces eco mode; below 10% it raises a proper alert.
• Heat under control. If the device runs hot on a summer night, Pevu first halves the frame rate and, if needed, switches video off — before the operating system kills the app.
• The parent device dims itself. After 30 seconds without a touch, all that remains is a nearly black display with a clock and a green dot. You're woken automatically — by noise, by trouble, by any alert.

Your setup for calm nights

1. Nursery device on the charger — any outlet will do.
2. Pick audio-only for the night; grab a picture with Peek when you want one.
3. Plug in the parent device too, or start with a full battery — it reports its level to the nursery unit.
4. Prefer 2.4 GHz Wi-Fi: it reaches further through walls than 5 GHz.
5. Before the first night, run the in-app night readiness check — it verifies volume, notifications and battery settings before it matters.

With that setup, the question from the top stops being a worry and becomes a checkbox. Exactly where it belongs.