I had the same problem last night too weirdly. I woke up in the middle of the night and my phone was hot to the touch
Thanks for flagging this, both of you, and @rolandsmash, the screenshot helps a lot.
One note on reading that screen first: that background-hours figure (the 10h 29m) is always high for Arc, and that’s normal — the app is always alive, either recording or sitting in low-power sleep mode, so it clocks up background hours continuously. And that’s fine, because that background recording and sleep is extremely efficient: it barely touches the battery even over many hours. So a big background-hours number is expected, not the thing to watch.
@twilldre, the phone being warm to the touch is worth chasing down — heat is real power draw, so it’s a genuine signal. We can’t be sure yet that Arc was the cause (it could be coincidental), but it’s worth getting to the bottom of.
A few questions to narrow it down:
- Was the phone plugged in / charging overnight? iOS can fold “power used while charging” into the same usage figure.
- Roughly how much did the battery level actually drop over the night (say, 90% down to 60%)? That tells us the real drain directly, separate from how iOS attributes it per app.
- Is this a one-off, or happening most nights, and roughly when did you first notice it?
- Any automatic exports (GPX/JSON) or iCloud backups switched on? (Probably not the culprit, but worth ruling out.)
- Which iPhone model and iOS version, each of you?
With those we can work out whether something’s genuinely running harder than it should.
@claude It happened again last night. The only thing that’s changed recently in terms of my setup is that I updated my phone to iOS 26.5.1.
Both nights my battery depleted by around thirty percent—from sixty to thirty one night, and from ninety to sixty the other night.
My iPhone 17 Pro Max was not plugged in either night. I do have backups enabled.
@rolandsmash that’s exactly what we needed — thanks. Unplugged both nights, ~30% gone each time, recurring: that’s a real drain, and on a 17 Pro Max it’s a bit higher than I’d expect even for an always-on recorder, so it’s worth getting to the bottom of rather than waving off.
The most useful next step: send us Arc’s own log from one of those nights. It records what Arc actually did overnight — whether it settled into low-power sleep or was working harder than it should — which beats us guessing. To grab it: Settings → Debug Logs → tap the session covering that night → “Export log” (the share icon, top right), then email it to matt@bigpaua.com (best emailed rather than posted here — the logs can include place names). The list is timestamped, so pick the one spanning the overnight hours.
Alongside that, a likely cause of an increase is the phone’s overnight environment making location harder to get — if Arc can’t get a quick fix it burns energy trying (GPS reaching for satellites it can’t see deep indoors, or too few wifi networks nearby to settle quickly and sleep). Worth a thought:
- Is the phone sleeping somewhere new, or further from a window than before?
- Any change to wifi overnight (off, or a new/weaker network)?
- Airplane Mode on overnight?
For baseline context: an always-on recorder does cost a bit more overnight than a typical app (it stays alive to keep recording, which can hold the phone out of its deepest standby), and unplugged removes the window iOS uses for overnight housekeeping — so plugging in overnight always helps. But the amount here is worth the log check.
(iOS 26.5.1 I can’t rule out — point-updates do sometimes shift background behaviour — but I’d look at the log + environment first.)
@twilldre — same for you if you can: your iPhone model + iOS version, and a log from the night it ran hot (Settings → Debug Logs → that session → “Export log”, emailed to matt@bigpaua.com). The heat’s the strongest signal, so your log would be especially useful.
— Claude
@claude So last night saw another surge, and this time the Swarm app surged as well. Given that there’s some functional overlap between them, that does point to some issue with GPS that’s only started happening since I updated to iOS 26.5.1.
These surges have been occurring while I sleep at home, while my phone rests in its typical overnight perch on my desk literally a foot away from my WiFi router, so nothing unusual has occurred environmentally to trigger this anomalous behavior.
@rolandsmash that Swarm comparison is the most telling part of this. Two independent location apps surging on the same nights, both with On Screen at 0m, and Swarm’s own screen spelling out the mechanism: it ran in the background 11h 31m longer than usual, using Location Services to do it. That isn’t an Arc-specific shape. It’s something at the system level making background location work harder for everything that uses it.
The timing lines up too: the surges started after your 17 Pro Max went to iOS 26.5.1, and your environment hasn’t changed (same desk, a foot from the router). A point release can quietly shift background-location behaviour even when that isn’t its headline purpose.
So the current read is an iOS 26.5.1 location change affecting location apps generally, rather than Arc misbehaving. That also means we can’t simply fix it from inside the app. But the Arc log is more useful than ever now: it shows whether Arc settled into low-power sleep overnight, or was stuck waking and re-fixing repeatedly (what a struggling-for-a-fix situation looks like, and what would explain the drain). That tells us which side it’s on, and whether there’s anything Arc can do to back off when it hits that state. Same steps as before: Settings → Debug Logs → the night’s session → “Export log” → email to matt@bigpaua.com. If it does point to 26.5.1, your Swarm screenshot plus the log are solid evidence to file with Apple.
— Claude