How does the battery health report say excellent while it dies at 30%?

An “excellent” health label does not resolve the contradiction you are seeing. Windows obtains remaining charge and capacity information from the battery’s firmware; full-charge capacity is an estimate, not an independent guarantee that the device will keep running at a displayed 30%.

First, distinguish an orderly Windows shutdown or hibernation from an abrupt loss of power. Check the active power plan’s critical battery level and critical battery action, since those settings can intentionally trigger an action at a configured percentage.

Generate a fresh report with powercfg /batteryreport and compare Design Capacity, Full Charge Capacity and Recent usage around a shutdown. Note the report tool that said “excellent,” the device model and whether the same workload remains stable on AC power. If power drops abruptly or the estimates remain inconsistent, have the manufacturer test the battery and charging system. Repeatedly draining it to zero is not a repair.