When evaluating 18v batteries, the most critical factor is the Cell Quality and Chemistry. Ensure the supplier uses Grade A Lithium-ion (Li-ion) cells from reputable brands (e.g., Samsung, LG, or high-quality domestic alternatives) to ensure stable voltage and longevity. Pay close attention to the Ampere-hour (Ah) rating, which determines the runtime; for professional use, 4.0Ah to 6.0Ah is standard, while 2.0Ah is suitable for lightweight DIY tasks. Additionally, verify the Battery Management System (BMS) functionality, which must provide overcharge, over-discharge, and short-circuit protection to prevent thermal runaway.