Here is how to find out if your iPhone 6s is eligible for a free battery replacement
How To Replace The iPhone 6's Battery
Amazon.com: Battery for iPhone 6S Replacement, Upgraded 3200mAh Higher Capacity Battery Replacement for iPhone 6S A1633/A1688/A1700 with Complete Professional Repair Tool : Cell Phones & Accessories
iPhone 6S Battery Replacement with Free Toolkit (1715 mAh Li-ion Battery) | Ramjet.com
Amazon.com: EMNT 4000 mAh Battery Compatible with iPhone 6s High Capacity A1633/A1688/A1700 Battery Replacement 【New Version】 with Repair Tool Kits and Instructions【2 Years Warranty】. : Cell Phones & Accessories
iPhone 6s Battery Replacement - with Tools – Battery World
Apple Repair iPhone 6 Battery Replacement Service
Amazon.com: SHENMZ Upgrade Battery for iPhone 6S, [3200mAh] 2023 New Version 0 Cycle Ultra High Capacity Battery Replacement for iPhone 6S Model A1633,A1688,A1700, No Tools : Cell Phones & Accessories
My DIY iPhone Battery Replacement Was Easy. Here's What I Did. - CNET