High-Pitched Squealing from Charging Case
A faint, high-pitched sound can be normal “coil whine” from the power circuitry while charging, but it should be minimal.
Change the power source. Try a different wall adapter (5V/1–2A) and outlet. Avoid fast-charge bricks.
Use a different USB cable. Low-quality cables can increase noise.
Inspect Tab seating. Reseat Tabs; slight misalignment can cause intermittent electrical noise.
If the squeal is loud, continuous, or new, stop using the case and contact support.