Cited as a reference
When lithium batteries catch fire: How overcharging can do bad things to Li-ion cells
Why people recommend it
Shows Li-ion cells being overcharged until they fail and burn; linked as a warning in threads about home-made chargers.
In their words
You can't charge a Lithium Battery with constant voltage; it will catch fire.
Marcus Müller on electronics.stackexchange.com, Apr 2020. CC BY-SA.
This is what happens if your charger doesn't work right.
JRE on electronics.stackexchange.com, Dec 2019. CC BY-SA.
However, if the lower voltage battery is not rechargeable, or already fully charged, you will damage it, and some types of battery don't like that.
user16324 on electronics.stackexchange.com, Sept 2021. CC BY-SA.
