Replacing iPhone 6s plus battery

Hi @newdouglas,

In general, the phone will work fine without gluing down the battery, but personally I'd advise against it. There are a lot of delicate parts inside an iPhone and having the battery loose means it can move around when the phone gets bumped or dropped and could possibly damage something else. It's also possible that over time contact with other components could wear through the coating on the battery, and expose the Lithium ion to air, which can be catastrophic, as in they can actually catch fire.

So yeah, for your own safety, you should probably glue it down. iFixit sells the adhesive used, and it's not particularly expensive.

iPhone 6 Plus/6s Plus/7 Plus Battery Adhesive Strips - iFixit Store

If even that cost is an issue, you can find battery adhesives on eBay and AliExpress for a song, depending on how long you're willing to wait for shipping.