For old macbook users (with magsafe connectors), covering the middle pin in connector stops charging the battery while running the laptop on main power supply.
That's excellent - thank you! I use my macbook at my desk quite a lot, and so usually it's plugged in and sat at 100% charge for hours (days?) at a time. So the ability to hold it at around a 40%-70% SOC is really useful
Yes, they have over-charge protection. But apple laptops still go all the way to 100% whenever you plug in.
It is not a good idea to charge a lithium battery to 100% all the time. The source article also specifically mentions it, giving reference to Battery University.