Will it damage the battery to have an iPad, iPhone, Mac, etc. plugged in constantly?

Apple has done considerable research and development regarding their batteries. They’ve developed intricate software, hardware and firmware to maximize battery performance and longevity. For instance, it’s not possible to fully discharge the batteries in their products. Also, charging is slowed as the battery nears capacity. These and other features extend the lifespan of the batteries in modern Apple products.

Apple does not address the specific issue of whether or not to leave their devices plugged in, though.

Batteries - Maximizing Performance - Apple

I have a 2015 MacBook Pro Retina, which is almost always plugged in. Never had any problem with it, until I read an article saying it should be periodically discharged and recharged. After doing that a few times, the battery expanded to the point it had to be replaced. I’ve since read many accounts of others having their own batteries expand after a few years. Did they keep them plugged in a lot, or were the batteries simply defective? They were all made about the same time as Samsung’s battery fires fiasco. Did Samsung get stuck with all the blame, when other companies were having similar issues with their own products?

The manufacture of lithium ion batteries is not a simple one. It’s surprisingly complicated and time-consuming to do properly. Even with the strictest quality controls, mistakes happen. Over the years, I’ve bought numerous aftermarket batteries. Every one of them turned out to be inferior to genuine OEM batteries. That’s the primary reason I paid Apple $200 to replace the battery in my MacBook. (The other reason was that I got a brand new keyboard and trackpad as part of the deal.)

Does anyone really know whether it’s detrimental to leave our devices plugged in? We know for sure that regular use wears all batteries out. We also know that letting them sit unused wears them out faster than using them.

hmmm…