Quote Originally Posted by Fencepost View Post

Connect a thin-gauge wire across a 9V battery and it will get hot enough to start a fire.
Please don't try this with a Lithium battery or the fire may be the battery itself and darn near impossible to extinguish before most of the lithium is burned up. FYI, lithium fires are dealt with through large quantities of water to cool them till either the fuel is expended or the amount of cooling from the water brings the lithium and it's container down to below it's flash point. Dropping a 9V lithium battery which is fully ignited into a bucket of water will not extinguish it immediately as you'd think it would Shorting, reverse charging, or too rapid a rate of charging or discharging are the main causes of Lithium battery fires, with too high of a discharge rate causing the battery to overheat and self-ignite running close behind. Lithium batteries can be seriously dangerous when damaged or abused!