What happened
On Monday morning, two patrol phones running the Citycare app with AI turned on became hot enough for iOS to step in. Both were in vehicles, running the camera and the AI model continuously, and both were plugged in for most of that time. Citycare records the phone’s own heat level, battery level and charging state with every GPS point, so we can replay the whole day minute by minute.
The pattern is consistent across all three phones used that day: continuous camera and AI work raises the phone’s heat level within minutes, and charging at the same time adds to it. Once a phone is hot, iOS protects the battery by slowing or pausing charging, which is why the battery level stopped rising even while plugged in.
Heat level of each phone through the day
Each band is one phone. The thin bar above a band marks when AI was running. Gaps mean the phone was not on a trip. Hover or tap for the minute-by-minute reading.
Share of trip time at each heat level
Why it seemed to improve in the afternoon
The afternoon phone (Phone C, an iPhone 13 Pro Max) stayed at the Serious level for most of its four hours on the road, while charging. It never reached Critical, the level where iOS shows the “needs to cool down” screen, so the crew did not see a warning. The larger Pro Max body spreads heat better, and the vehicle was moving for most of the afternoon, which helps the phone shed heat. The underlying load was the same.
Phone timelines, 07:00 to 19:00
Each phone has its own timeline with five stacked readings on the same clock: heat level, charging state, battery level, AI detections and vehicle speed. Hover or tap anywhere on a timeline to read every value for that minute.
Charging while the AI runs
We looked at every 10-minute stretch of driving in Vaughan since October 8 and measured how fast the battery rose or fell, grouped by whether the phone was plugged in and whether AI was running.
Median battery change in percentage points per hour. iPhones report battery in 5 % steps, so single 10-minute readings are rounded; the medians across many stretches are reliable.
What the numbers show
- With AI off, the in-vehicle chargers work well: phones gained about 45 % per hour.
- With AI on and unplugged, phones lost about 30 % per hour. That is the extra energy the camera and AI model use.
- With AI on and plugged in, the battery held flat. Every one of those 32 stretches was at the Serious or Critical heat level. In that state iOS slows or pauses charging to protect the battery.
- The charger in truck 13553 had enough power. Between 12:43 and 13:47, Phone B gained 25 % while running AI at the Critical level. The flat battery at other times comes from heat, not a weak charger.
Charging connection drops
How many times per hour each phone switched between charging and not charging while on a trip. Frequent switching while the phone is cool usually points to a loose cable, a worn port or a wireless charger losing alignment.
Wireless and MagSafe chargers
Wireless charging, including MagSafe, turns more of its power into heat than a cable does, and releases that heat through the back of the phone, right at the battery. Independent testing by iFixit measured MagSafe using about 36 % more energy than wired charging, and noticeably less efficient when the phone sits slightly off centre. Apple notes that a phone may charge more slowly, or stop above 80 %, when it gets warm.
For phones running AI patrol, that extra heat lands on a phone that is already working hard. Our data does not record which type of charger was used, so we cannot say whether wireless charging played a part on Monday. For AI patrol phones, we recommend a wired USB-C connection.
AI detections over the day
Every detection the AI saved during the day, in 15-minute intervals, for each phone. Detections are grouped by what the AI identified.
Detections by type
Detections per hour of AI time, by heat level
Detections depend mostly on what is on the road, so this is a rough guide. Use it to check whether the phone kept capturing while hot.
AI sessions
Recommendations
These steps keep the phone cooler while AI patrol is running, without giving up charging.
- Charge with a cable, not wirelessly. Use a USB-C cable into a 20 W or stronger USB-C car charger. Avoid MagSafe and other wireless mounts on phones that run AI patrol.
- Keep the mount away from the heater vents. In the colder months, a vent clip with the heat on warms the phone directly. A dash or windshield mount works better.
- Keep the phone out of direct sun when the vehicle is parked, so it does not start the next drive already warm.
- Remove thick or rugged cases while the phone is in the mount. They hold heat in.
- Start each shift with a charged phone. A phone that is not also charging hard from a low battery stays cooler.
- Check the cable is seated firmly. A loose cable makes charging start and stop, which shows up in our data as connection drops.
What we are doing
We are working on an app update that automatically eases the AI workload when a phone gets hot, and pauses the AI if it reaches the Critical level. GPS routing keeps running throughout, and AI resumes on its own once the phone cools down. We will share timing once it is ready for testing.
How we measured
- Source. Citycare stores a reading with every GPS point a phone records on a trip, roughly once a second. Each reading includes the phone’s heat level, battery level and charging state as reported by iOS, along with speed. This report uses 12,000+ readings from three phones on November 2, grouped by minute.
- Heat level. iOS reports a thermal state rather than a temperature in degrees. Apple defines four levels: Normal; Fair (slightly warm); Serious (hot, and iOS begins limiting the phone and its charging); Critical (very hot, and iOS may slow the phone heavily and show a cool-down screen). iPhones do not give apps a temperature reading in degrees.
- Battery. iOS reports battery level in 5 % steps.
- Charging state. iOS tells apps whether the phone is charging, but not what kind of charger is connected (wired or wireless) or its wattage.
- AI time. From the start and end of each AI learning session recorded by the app.
- Detections. Every detection saved by the AI, timed by the moment it was captured.
- Privacy. Phones are labelled A, B and C. This report contains no names or locations.