Ten minutes on the phone screen is effortless. Two hours of Windows installation is a different story - the phone is powering the card, decoding video and lighting the screen at once.
Short checks barely touch the battery, which is why nobody warns you about this on day one. Then comes the long job - a full Windows install, a server recovery, an hour of setup screens - and the phone is at 15 percent and uncomfortably warm. This page explains why the drain and heat happen, what they do to the feed, and the practical fixes technicians actually use.
Three loads run at the same time. The display stays on continuously at working brightness - normally the largest battery consumer a phone has. The processor decompresses the USB video feed without pause; video decoding is real work, not an idle task. And the capture card itself is powered by the phone through the USB connection, a steady extra draw most people forget entirely.
Together these can take a healthy phone from full to empty in a few hours of continuous use - faster on an older battery. Plan a long session the way you would plan a long call on speakerphone: assume the charger needs to be part of the setup.
The clean solution is a USB-C hub with power delivery pass-through. It sits between the phone and everything else: your normal charger feeds the hub, the hub powers the phone and the capture card together, and the data path to the card runs through the same hub.
Not every hub passes USB data and charging to every phone model, so test yours at home once. When it works, session length stops being limited by the phone at all - only by your patience.
Sustained decoding plus charging warms any phone. Past a point, the phone protects itself by thermal throttling: the processor slows, and the feed starts to stutter or drop frames - which looks exactly like a capture card fault and sends people debugging the wrong device.
The countermeasures are unglamorous and effective: take the phone out of its case during long sessions, keep it off soft surfaces and out of sun, drop screen brightness to the lowest comfortable level (the screen is also a heat source), and if the feed starts stuttering after an hour of smooth work, suspect temperature before hardware. A short cool-down break restores full smoothness - a broken card would not recover like that.
For long recovery jobs, watch how the video session is powered - the charger is part of the setup, not an afterthought.
Watch Full VideoYes, with the right hardware: a USB-C hub with power delivery pass-through. A plain OTG adapter usually blocks charging because the phone's single port is busy acting as USB host. The hub is the standard way technicians run long sessions.
Occasional long sessions are normal use. Daily all-day sessions combine three things batteries dislike - heat, staying near full charge, and constant heavy discharge or charge cycling. For a permanent daily setup, a small dedicated monitor is kinder and cheaper in the long run.
Most likely thermal throttling or the phone aggressively saving power. Cool the phone, lower the brightness, close and reopen the viewer app, and check whether your brand's OTG setting switched itself off. If it recovers after cooling, the hardware is fine.