Smartphone battery overheating: What are the symptoms?

My South Korean made smartphones have had a tendency to overheat and the latest one is no exception. It got really hot and then began to emit a “stress due to being heated” sort of sound (hard to describe), and things have now gotten to the point where I’m afraid to even turn the phone on or hook it up to a charger.

Suppose that a battery really overheated during phone use. What would be the symptoms? Screen suddenly goes black? Phone makes hissing sound? Smoke comes out?

Battery catches fire, bursts, small explosion…

Not kidding. The mere fact the battery is venting (“battery under stress sound”) means that it’s failing. Stop using it. Power down the device. Remove and safely dispose of the battery if possible. Replace the battery or, if necessary, the device.

ETA: I’m jumping to the conclusion that this is a catastrophic LiPo battery failure in the making, simply because a safe non-failing battery makes no noise, EVER. If it’s sounding off while overheating, that’s a very bad thing.

yikes, ok, thanks.

if the battery is removable, pull it out and see if it’s starting to swell/bulge. if it is, get it away from anything combustible.

Just in case you think these concerns are overblown: Link A quick youtube search will yield a whole bunch of other vids.

Is there such a thing as subtle LIPO battery overheating - enough to be bad but display no symptoms?