Short answer: buy a powered hub with its own adapter, sized at roughly 12 W per phone, with charging-capable ports, and keep it to around seven to ten phones per hub on separate Mac ports. Use short certified data cables. Nearly every "my phone keeps disconnecting" report on a rack is a power problem, not software.
Why iPhones drop off a USB hub
A phone that is charging and being driven draws much more than an idle one. When the hub cannot supply it, voltage sags, the phone browns out, and it disconnects from USB mid-run. It comes back a moment later and looks like a flaky cable or a crashed app. Unpowered hubs make this worse: they split the Mac's own port power between every phone.
How much power per phone?
Apple's own 12 W adapter is the one most iPhones were designed around, so 12 W per port is a safe planning figure. A hub whose adapter is smaller than 12 W × the number of phones will run fine when the phones are idle and fail when they are all working at once — which is exactly when it matters.
| Phones on the hub | Adapter to look for |
|---|---|
| 4 | 50 W or more |
| 7 | 85 W or more |
| 10 | 120 W or more |
| 16 | 200 W or more, or split across two hubs |
How many phones per hub, and per Mac?
- Bandwidth. Lightning iPhones, and the base iPhone 15 and 16, transfer at USB 2 speed (480 Mbps), and every USB 2 device on a hub shares that one lane. Clips move over the same cable, so a crowded hub means slower delivery.
- Chaining. USB allows hubs to be chained, but every chained hub shares the upstream port. Put each hub on its own port on the Mac instead.
- Real-world data. On the Appium forum, one operator described running 25 iPhones across four 7-port hubs and recommended industrial-grade hubs over consumer ones (thread, May 2024).
- Farmero's own figure: four phones at once on one Mac, the most we have measured. We will publish a higher number when we have run it.
What to look for when buying
- External power adapter, with the wattage printed — not "up to".
- Charging data ports (often labelled BC 1.2 or CDP), so each port both charges and carries data.
- Individual port switches — handy for power-cycling one phone without touching the rest.
- Metal housing and spacing between ports. Industrial or "charging station" hubs outlast desk hubs on a 24/7 load.
- A short, fixed upstream cable to the Mac.
Cables
- Data cables, not charge-only. A charge-only cable never shows the phone to the Mac.
- Under a metre, MFi-certified. Long and cheap cables are where "the phone vanished mid-run" usually comes from.
- Label both ends with the phone's name. On a rack of ten, this saves hours.
Related guides
- iPhone keeps disconnecting from Mac — a troubleshooting tree
- Phone farm rack setup — shelves, stands, cables, labels
- How to scale a phone farm to 50 phones — what changes
- Running several phones
FAQ
Why does my iPhone keep disconnecting from the USB hub?
Most often the hub cannot supply enough power while the phone is charging and working. Use a powered hub sized at about 12 W per phone, then rule out the cable.
Can I plug iPhones straight into the Mac?
Yes, for one or two phones. Past that, the Mac's ports cannot keep several working phones charged.
Do USB 3 hubs make iPhones faster?
Only for phones and cables that support USB 3 (Pro models from the iPhone 15 Pro, with a USB 3 cable). Lightning iPhones run at USB 2 speed on any hub.
Should I chain several hubs together?
Avoid it. Chained hubs share one upstream port. Give each hub its own Mac port.
Does Wi-Fi work instead of cables?
Farmero drives phones over USB only. The cable also carries the clips and the power, which is why it is the more reliable choice.