8 grams of lithium-what?

| Comments (5) | Outstanding! Security: Airport
Schneier notes the TSA's new rules about lithium ion batteries. Here's their overall policy:
The following quantity limits apply to both your spare and installed batteries. The limits are expressed in grams of “equivalent lithium content.” 8 grams of equivalent lithium content is approximately 100 watt-hours. 25 grams is approximately 300 watt-hours:
  • Under the new rules, you can bring batteries with up to 8-gram equivalent lithium content. All lithium ion batteries in cell phones are below 8 gram equivalent lithium content. Nearly all laptop computers also are below this quantity threshold.
  • You can also bring up to two spare batteries with an aggregate equivalent lithium content of up to 25 grams, in addition to any batteries that fall below the 8-gram threshold. Examples of two types of lithium ion batteries with equivalent lithium content over 8 grams but below 25 are shown below.
  • For a lithium metal battery, whether installed in a device or carried as a spare, the limit on lithium content is 2 grams of lithium metal per battery. Almost all consumer-type lithium metal batteries are below 2 grams of lithium metal. But if you are unsure, contact the manufacturer!

This seems like it will be a lot of fun. I'm really looking forward to watching TSA reps try to figure out whether a given device has over 8-gram equivalents of lithium in it, let alone trying to add up the watt hours in various devices to decide if they are over 300 (note that 8 grams is claimed to be about 100 watt-hours, so what if you have 302 watt-hours, which is over 300, but probably less than 25 grams). This "contact the manufacturer" thing is pretty nuts. TSA needs to have a list to decide what they want to accept. Why don't they just publish it?

Another thing that's weird is that you can't have spare batteries in your checked luggage, but you are allowed to have such batteries installed in your devices. I'm sure my laptop will contain any fires or explosions. Outstanding!


I think the issue with batteries in checked luggage is that the automated fire suppression system in the cargo hold may not be up to the job.

With carry-on, the flight attendant can keep using fire extinguishers until it's out, throwing his or her body onto the flaming battery as a last resort ;-)

Seriously, is this based on any actual observed problem other than some manager watching a flaming battery on YouTube?

See Schneier's updated blog article, a UPS plane caught fire back in 2006:


Yeah, I saw that. Hence my comment about the cargo hold fire suppression system.

But presumably those batteries weren't the _source_ of the fire. I can't see how batteries not being drained or charged would spontaneously ignite. Though it doesn't say one way or the other in the article.

Any fire in the passenger compartment that starts igniting quiescent lithium batteries is already really bad news for the people in seats.

So what real issue is driving the carry on restrictions? Airplanes are a major concentration of people draining lithium batteries as they use their laptops, DVD players, and iPods. You'd think if there's any significant chance of ignition, we'd have seen it.

The checked luggage prohibitions (installed vs loose) are likely related to accidental shorts (as opposed to spontaneous ignition) since contact with a metallic substance could release a lot of energy in a short period of time, leading to a fire.

The whole thing (TSA information) is poorly written and hard to digest, they don't take the time to call out the distinction between Li-ION and Li-Metal batteries, which makes the chart read as though it contains self-inconsistencies. (*sigh*) More hassle for the regular traveler.


The regulations are written with incredible opacity but actually make sense...

Loose lithium batteries which can short are a real hazard. In a device, powered off, they are far less likely to short & ignite.

LiIon are far less worrysome than Li metal (nonrechargeable).

The grams of lithium bit make sense for shipper regulations (which is where they probably came from, this is I believe DOT not TSA doing), but are confusing for Joe Average.

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