How do I check a laptop's battery health before or after buying?

On Windows, open Command Prompt as administrator and run powercfg /batteryreport; this generates an HTML report showing design capacity, full-charge capacity and cycle count. On macOS, hold Option and click the battery icon to see condition, or go to System Information under Power for full cycle-count history. The ratio of full-charge capacity to design capacity gives you effective battery health as a percentage. Before buying from Edify, this check is done for you: the 31-category Final Quality Check includes a battery-health assessment at the certification stage. After delivery, if you find the battery performance does not match what was represented, contact support within the 14-day return window and it will be made right.