Could you please dummy down the lithium charger info for the technically challenged among us?
Lithium batteries are prone to spontaneous combustion.
Sure thing.
A little lithium battery background. When a non-lithium battery is overcharged, it will usually just get hot. Ditto when it's over-discharged. When a lithium battery is overcharged or over-discharged, it develops internal shorts.
With enough of these shorts the battery will enter what's known as thermal run-away. IOW, the internals start to break-down producing heat, which starts to cook the lithium in the battery. This produces toxic white smoke that will turn the flat pack into a silver sausage. Eventually, the mylar outer skin will burst exposing the lithium to the air.
When this happens, the lithium catches fire.
Here's a pic of a LIPO (lithium polymer) battery pack. These are the type of lithium batteries used in most consumer electronics, such as phones, etc.
See the circuit board that's located where the red and black wires enter the pack? That's the protection circuit. It's constantly monitoring pack voltage to prevent overcharges or over-discharges.
Here's a LIPO that doesn't have the circuit.
Here's a pic of a normal hobby LIPO and one that's puffed, meaning it's developed internal shorts and should not be used.