The cells are in plastic bag with a lot of room to swell and doesn't explode. If you have lipo cells in a closed container it may shortcircuit and explode if they cannot expand. Unidens battery are held together by electrical tape to allow them to swell without resistance.
If you have a firecracker or a rifle bullet and take them apart and pour out the gunpowder and ignite it, it will only burn and not explode. It's the expansion against a solid container that will build up pressure and will then burst and release the explosion.
/Ubbe
Under the fire and explosion investigation definition, an explosion is a physical reaction characterized by the presence of four major elements or criteria:
(1.) Rapid Increase in Gas Pressure (Gas Dynamic)
(2.) Confinement of the Pressure
(3.) Rapid release of that Pressure
(4.) Damage or Change to the confining structure of the vessel
"Noise is not an element"
"Explosion Investigation and Analysis, Kennedy on Explosions"; Kennedy, Patrick M. and Kennedy, John P15-16
There is also the rate at which the gunpowder burns to be considered. Black powder burns at a different rate than smokeless powder for example… and as you say, containment also plays into the difference between a rapid burn and an explosion. But are all four elements present? I don’t know where they draw the line determining when a rapid burn turns into an explosion but In the fire service it’s that burn rate that classified an explosion. A “charged house” is a house that is on fire (a fire which has banked down), the rate of burn is slowed due to the lack of oxygen… until someone opens an outside door or window, allowing a supply of oxygen to mix with the flammable gasses inside, the results are a rapid burn that imitates an explosion but is referred to as a “blow back”. If it’s you that opened up the front door you will find yourself blown out into the front yard. That’s why you see the FD cutting holes in the roof… in an effort to “vent” the hot gasses out of the house first, before attempting to gain access… no blow back. The interior fire will increase but not at a rate that increases so much in intensity as to cause what most would refer to as an explosion, that rapid expansion of gasses that creates pressures strong enough to knock you off your feet or propel you backwards.
It’s interesting that OSHA says a MSDS is not needed for the battery Uniden uses in its SDS100 because if it were susceptible to exploding a MSDS would be required… and since we haven’t heard of these batteries doing anything worse than swelling, I wonder what it is that prevents fire and explosions. My guess is the composition of the battery differs from a true definition of a Lithium ion LiPo battery enough to not have the same characteristics as what we know to be true Li-Po’s that can exhibit fires and explosions, but still qualify as a LI-Po. Maybe it’s simply the physical size, meaning the battery doesn’t contain enough of the material that would allow it to heat up to a temperature hot enough to start a fire. I guess a chemist could be consulted to get an answer to that.
