Battery replacement for 6S

Yes, it can still be replaced. It will cost $69. See this link --> iPhone Battery Repair & Replacement - Apple Support

While getting a new battery is much less expensive than buying a new iPhone, keep in mind your phone cannot support the newer iOS versions and it won't be long before some apps, particularly 3rd part apps stop running on such an old iPhone. Whether putting money into an old outdated iPhone is a good investment only you can decide. I wouldn't do it myself.

JEMMSC wrote:

Can the 6S battery still be replaced?

Here is how to check that in your country or region, and how to get pricing:

… iPhone Battery Repair & Replacement - Apple Support

An iPhone 6s should be running iOS 15, that’s currently iOS 15.7.6, as well.

… Update your iPhone or iPad - Apple Support

Click on the link 🖇️ iPhone Battery Repair & Replacement - Apple Support (IN)