Hi @nathanbrantley,
Thank you for being so patient while I dug around for a good answer.
I chatted with a few folks and I was given a few resources from some people that have been around iFixit longer than I have. The first was an Answers Forum Post that answers this question really well: [link|https://www.ifixit.com/Answers/View/503737/Are+ifixit+replacement+batteries+better+then+say+battery+from+eBay|Are ifixit replacement batteries better then say battery from eBay?] The second thing I was given was an article we published in 2020 that shares how we go about testing batteries, in-house: [link|https://www.ifixit.com/News/34324/how-we-test-the-quality-of-batteries-we-sell-at-ifixit|How We Test the Quality of Batteries We Sell at iFixit].
We have a stellar group of people behind our Customer Service team that will help you if you find yourself having an issue with something you buy from use–I can’t say Amazon ''isn’t'' helpful, but I can say I know our team and they’re amazing and knowledgeable about our products.
We also back our products–check out our [link|https://help.ifixit.com/article/50-warranty#:~:text=OF%20OUR%20PRODUCTS.-,Consumables,-Some%20products%2C%20like|Warranty information on Consumables] (eg., batteries) to learn more about how they’re covered.
Let me know if you have more questions!
