Exploding Flashlights and How to Protect Yourself

Exploding Olights

There’s been an uptick in talk online in the flashlight, EDC and gun communities about exploding flashlights. Most often referenced is the case of Caleb Joyner. Caleb was holding a flashlight in his mouth while working on his car when the flashlight exploded. The reason this case is mentioned so often is because the estate sued the flashlight company and the court documents are public, revealing what occurred, and the flashlight make and model.

In Caleb’s case, he was using an Olight T20. (If this is a light you own, I suggest purchasing a more modern alternative, eg. the Olight M2R Warrior. Keep reading to find out why!) Interestingly, if you read the case documents, there are no claims that the flashlight exploded, or even that the flashlight caused the explosion. The case is primarily based on the accusation that Olight didn’t provide adequate documentation warning of the possibility that batteries can explode.

The Nuon batteries inside the Olight Flashlight exploded in
Mr. Joyner’s mouth, causing the flashlight to become lodged in the back of his throat.

Caleb Joyner vs Olight

There have been many other occurrences, here are cases with a Solarforce L2P, Surefire G2 and Surefire M6.

So flashlights are exploding. What’s going on?

It is easy to blame the flashlight.  But that idea should lead to a raised eyebrow.  A flashlight is mostly an inert tube of metal, with very little combustible material, and we’ve seen that it occurs with many different brands.  The batteries, on the other hand, are a potent source of energy.  And it is the batteries that are the root of the problem.

Unsurprisingly, it is lithium batteries that are causing the exploding flashlights.  However, these aren’t the lithium batteries that you’ve heard about in tablets, hoverboards, and vapes.  It is an entirely different type of lithium battery, that most people are unfamiliar with, but actually has a longer history.

Are lithium batteries dangerous?

Fundamentally speaking, there are two types of lithium battery: lithium-ion and lithium-metal.  Lithium-ion gets all the press.  It is rechargeable and powers everything from smartphones to electric vehicles.  And despite the occasional news bite of them catching on fire, they are actually pretty darn safe when you consider the billions of them in use every day.

Lithium-metal is an older, simpler type of battery.  They aren’t rechargeable and actually use 2x or 3x more elemental lithium than a similar li-ion battery would.  All of the cases referenced above use a specific battery and circuit. The particular style of lithium-metal battery we are looking at today is called a CR123A.  They pack a lot of energy for how light they are, and they are favored for their 10 year shelf life.  Originally a specialized camera battery, they’ve been used for flashlights ever since 1988 when Surefire released the first tactical handheld flashlight.  Yes, these batteries have been in use for more than 30 years.  And they have been exploding occasionally all that time.  Despite popular rhetoric, the accidents aren’t any more likely to happen to any particular brand.

Panasonic CR123A battery
Panasonic CR123A battery commonly used in flashlights

How does a CR123A battery explode?

It all starts when two (or more) different CR123A batteries are mixed.  They are put into a flashlight and used.  Both batteries are discharged.  But as they run down something curious happens to the weaker battery: after it reaches zero, it becomes reverse charged.  This is not the same as recharging a non-rechargeable battery.  When recharging, electricity is forced back into a battery, causing the voltage to increase.  Reverse charging is more like normal discharging, except that it keeps going past where the battery would be considered dead.

illustration of reverse charging in a two cell series flashlight
In both images, both batteries are bein depleted at the same rate. However when one battery is already partially depleted, the battery voltage tries to go negative.

This diagram should help clear things up.  The first example is a normal situation.  Both batteries start fully charged and run down to zero volts.  The second example shows a fresh battery paired with a mostly-dead battery.  The fresh battery has a straight line from full to empty.  The mostly-dead battery also has a straight line, but it doesn’t stop at empty.  Instead it goes below empty, below zero volts, into negative voltage.  The good battery completes the circuit by shoving electricity through the dead battery as if it weren’t there.

Two battery flashlight circuit design with the batteries in series
Two battery series circuit design. 2xCR123A flashlights designed like this have the highest risk of explosions.

This is where all the problems happen!  Reverse charging a CR123A is exceptionally dangerous.  It gets hot and release gases.  Pressure builds up.  In a waterproof IPX8 sealed flashlight that pressure is trapped.  When the pressure gets high enough, the flashlight will explode.

It gets worse.

You might think that you are already having a pretty bad day if your flashlight explodes.  But give a moment’s thought to the gasses streaming out of the battery.  They aren’t good.  The batteries contain a cocktail of energetic compounds, and none of them smell like roses.  The cheapest CR123A might even produce hydrofluoric acid gas.  Other major compounds in the battery include perchlorate and dimethoxyethane.  If a CR123A ever explodes or burns, get it outside as quickly as possible, and limit your own exposure to the fumes.

How do you prevent exploding flashlights and protect yourself?

First and foremost: Do not use CR123A,except where absolutely necessary.  We’ve got better alternatives now.  Rechargeable batteries are safer and will save you hundreds of dollars. Here’s a long list of flashlights that accept rechargeable batteries and often outperform 2xCR123 lights

But let’s say you’ve got a few lights where it isn’t feasible.  A good example is emergency lights or weapon lights that you want ready yet are rarely used.  Here are some best practices for safely using CR123A:

  • Never mix old and new batteries.
  • Don’t mix batteries from different brands.
  • Don’t mix batteries that are the same brand, but manufactured in different years.
  • Replace dying batteries early, and don’t try to squeeze every last drop out.
  • Check your batteries occasionally with a multimeter or a specialized battery tester
  • Only use Panasonic (or other made-in-US) CR123A.

If you think it is wasteful to discard CR123A that still have some life to them, don’t use CR123A.  Get rechargeables instead.  Most modern flashlights the size of 2xCR123A lights use a rechargeable 18650 battery. Or consider getting a flashlight that only uses a single CR123A.  A single battery can’t be reverse charged.

A multimeter is a tool that can measure voltages.  Periodically checking the voltage of both CR123A batteries will allow you to spot an imbalance earlier.  If they are more than 0.1 volts apart they shouldn’t be used.

Who makes the best and safest CR123A?

Panasonic makes the safest CR123A batteries (and they can be purchased in packs of up to 20).  There are two major reasons for this: in 2015 they reformulated the batteries so that they no longer contained any fluorine compounds, making it impossible to produce hydrofluoric acid.  And their CR123A contain a “positive temperature coefficient” safety or PTC.  The PTC kicks in when the temperature gets dangerously high, limiting the flow of electricity and slowing the runaway reaction.  However, it isn’t perfect.  Treat any CR123A as if it could vent when abused.

Panasonic operates a factory in the US which produces them, and this appears to be the only such factory in the US.  Any US-made CR123A likely came from the Panasonic factory and is safer than non-Panasonic batteries.  Cheaper Chinese batteries will likely omit the PTC to save a little money, and they probably still use the older fluorine-based chemistry.

It is very unfortunate that people have been hurt by these batteries in exploding flashlights.  Particularly when it is so preventable.  Use rechargeable batteries.  They are far less costly in every sense.

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