Copied this from a Dept. of Energy site. Long thread but might be useful if you use this type of lithium battery.
CR123 Type Flashlight Batteries Have Potential to Explode
Originator: Lawrence Livermore National Laboratory
Statement: CR123-type lithium batteries used in flashlights have overheated, exploded, and even caused fires. The quality of some of these batteries is suspect and may have caused or contributed to these events.
Discussion: Recently, at another DOE site, personnel traveling in their van heard a loud “pop” and saw flames in the rear interior of the van. Upon investigating, they discovered that a tactical, high-intensity LED-type flashlight had exploded and started some nearby combustible materials on fire. The fire was extinguished with minimal damage to the van or equipment. No one was injured. It was concluded that the batteries in the flashlight had failed catastrophically.
In June, the batteries in a flashlight used by an LLNL employee failed in a similar way. (See Figures 1 and 2.) The worker tried to use the Surefire LED flashlight earlier in the day but found it was not working. Later on, he heard a “bang” from the flashlight case, which was emitting smoke. He monitored the flashlight until it was safe to handle. Fortunately, the heat damage was contained to the inside of the flashlight case and there were no injuries or other damage.
Both of these flashlights used CR123-type, lithium-primary (non-rechargeable) battery cells manufactured overseas.
Analysis: • The lithium battery cells used in both of these incidents were from foreign manufacturers. Searches of similar incidents on the Internet revealed cases where foreign-made CR123 lithium batteries (mostly from China but some from Japan) have exploded—some quite powerfully—and have caused injury. There have been no reported events of explosions from batteries made in the United States.
• Investigations of some of these events by the flashlight manufacturers and other experts have shown that the explosions may have been caused by using inferior, foreign-made batteries, mixing of batteries from different manufacturers, mixing lithium primary cells with lithium-ion rechargeable cells, or mixing batteries with different levels of charge.
• Mixing different brands of batteries, non-rechargeable primary batteries with rechargeable ones, or batteries with different charge levels may cause one of the cells (the stronger cell) to overheat when it discharges rapidly in order to compensate for the weaker cell. This can occur when mixing batteries, as discussed above, even if using batteries made in the United States.
• Foreign battery manufacturers may not have the same level of quality control as those made in this country. CR123-type lithium batteries are usually equipped with vents and thermal discharge protection features that are designed to prevent the cells from overheating. In examining some of the foreign-made cells, these safety devices did not function properly or were not installed.
• Most tactical and high-performance flashlights have watertight casings, sealed with O-rings. This feature was cited as one of the reasons why the flashlights exploded. The gases inside were not allowed to vent and, subsequently, the pressure exerted by the gases or their ignition caused these flashlights to explode.
Actions: 1. Use only batteries recommended by the flashlight manufacturer; be cautious of batteries that are a “generic” brand or manufactured outside the United States. Check existing flashlights for the proper batteries.
2. NEVER mix different brands of batteries and NEVER mix 3.0-volt lithium primary cells with
3.7-volt lithium-Ion rechargeable cells.
3. ALWAYS use batteries that have similar levels of charge. This can usually be assured by purchasing batteries together. If you are unsure of the charge level, DO NOT USE THEM.
4. If your flashlight does not light when it is turned on, remember to turn the switch back off to prevent the batteries from discharging and overheating.
5. If your flashlight is acting abnormally—such as making sounds, vibrating, or emitting smoke/fumes—put it down in a safe area, keep away from it, and seek assistance.
Priority Descriptor: Yellow / Caution