Lithium-Ion (Li-ion) Batteries
Carriage on Passenger Aircraft
Compliance with DOT Regulations of July 31, 2007
(Changes to 49 CFR parts 171, 172, 173, & 175)


On December 28, 2007, the Department of Transportation (DOT) and the Transportation Security Administration (TSA) jointly publicized regulatory changes that would take effect on January 1, 2008.  These regulations set new restrictions on the size of both lithium-ion (secondary or rechargeable) and lithium metal (primary or non-rechargeable) batteries that could be carried aboard passenger aircraft, or which could be placed in checked baggage.

There was a certain degree of confusion in the media and on the part of individual citizens regarding these rules.  If was often misreported that these were TSA regulations -- the assumption then being that they were the result of security concerns.  In fact, the regulatory package is the result of years of work arising out of several incidents involving fires aboard or near aircraft.  These fires involved both lithium-ion and lithium metal batteries.  Investigation of the incidents showed that aircraft onboard fire suppression systems could not always extinguish lithium batteries fires.  In fact, the bulk of these new regulations are intended to harmonize commercial shipments in the U.S. with regulations that have been developed internationally.  The part of the regulations that most concerns airline passengers is found in 49 CFR 175 and amounts to a way of allowing airline passengers to bring common battery powered consumer goods along with them when traveling.

The problem was that DOT and TSA did not adequately explain the new regulations in terms that consumers could understand.  The wording on the web sites is sometimes ambiguous, and the table shown on the DOT site does not operationalize the information for the average traveler.  That traveler, holding a lithium battery in his/her hand, or knowing that there is one in a laptop, camera, cellular phone, or PDA, just wants to know what can be carried aboard the plane, what can be checked, and what can't go at all.

Thankfully, almost any intact consumer grade lithium-ion rechargeable batteries can go on the aircraft, carry-on or checked, depending upon the "equivalent lithium content" (ELC) of the batteries or cells.

DISCLAIMER:  The information presented on this page has not been approved or endorsed by DOT or TSA.  It represents my best effort to determine compliance measures based on information from the DOT and TSA websites, and from examination of the Final Rule published in the Federal Register on August 9, 2007.  (Both DOT and the FAA were contacted for review of the main decision aid that follows, but did not provide comment or any substantive information.)


Li-ion Battery Decision Aid

Here's a decision aid for travelers.  "Installed" batteries are those that are inside the device which they power.  "Spare" batteries are extra batteries.  This aid is for lithium-ion rechargeable ("secondary" in the language of the regulations) batteries only.

  • The blue-gray boxes on the left of each column represent batteries.  The number in the box represent the grams of "equivalent lithium content" (ELC) of each battery.
  • Green boxes represent permitted carriage.
  • Yellow boxes represent carriage with restrictions.
  • Red boxes represent prohibited carriage.


  • 1 - Device power positively secured.
  • 2 - Battery terminals protected.
  • 3 - A total of no more than two batteries in this ELC range per passenger.  This is for any combination of "spare" batteries in carry-on, or "installed" batteries checked or in carry-on.  The aggregate ELC of both batteries cannot exceed 25 grams.  The aggregate ELC of batteries in this category is independent of batteries whose ELC is less than 8 grams.


Equivalent Lithium Content (ELC)

This is the root of much of the confusion.  At this point in time, the average consumer must determine on his/her own what the ELC is for each type of battery carried.  Expect to see information posted on manufacturers' web sites sometime in the future, but in the meanwhile, you may be able to calculate ELC yourself.

First a little terminology:

  • Battery:  A battery typically consists of one of more lithium-ion cells in a plastic case.  The cases come in a variety of sizes and shapes.
  • Cell:  Cells are the actual power producing components.  They may be cylindrical or rectangular.  Typical consumer applications will have between one and 9 cells per battery -- but sometimes only a single cell, or as many as a dozen.  It is important to know the number of cells if you are calculating you own battery's ELC.
  • mAh:  Milliampere-hour.  1/1000 of an ampere-hour.  This is the most common designation of a battery's capacity and is usually printed on the battery's label, such as "1500 mAh".
  • Ah:  Ampere-hour.  The amount of electric charge transferred by a steady current of one ampere for one hour.  At a given voltage, the higher the ah or mAh rating, the longer the battery will last under a given load.

Single Cell Calculation

The reason that the above terms are important is that they are used in the ELC calculation.  That formula, for a single cell is:

ah x .3 = grams ELC

A typical lithium-ion cell used in many camera batteries has a rated capacity of 1500 mAh (1.5 Ah).  So the formula for just that single cell would be:

1.5 x .3 = .45 grams ELC


Multi-Cell Battery Calculation (Simple Battery)

But remember that most batteries contain two or more cells.  In the case of some common batteries used in digital single lens reflex (DSLR) cameras (Fujifilm's NP-150, Nikon's EN-EL3e, Olympus' BLM-1, etc.), there are two 1500 mAh cells in each battery.  The label on the battery will state the voltage and the ampere-hour rating.  A simplified layout of one of these batteries is shown below:

Note that the cells are wired in series to double the voltage of a single cell (from 3.6 to 7.2 volts), but because of this series wiring, the ampere rating remains the same (1500 mAh).  In this situation, it is correct to use the mAh rating from the battery label, but you will need to know the number of cells.

The final calculation step for this battery (made up of two of the cells we used for the calculation above) would be to multiply the number of cells by the ELC of a single cell:  .45 x 2 = .9.  The ELC for this battery is .9 grams.  That places this particular battery in the "small" battery category and there are no regulatory restrictions to the number of these batteries you can carry aboard.


Multi-Cell Battery Calculation (Large Laptop Battery)

More complicated are the higher capacity batteries used in laptop computers.  They are often constructed with cells wired both in series and in parallel.  Wiring cells in series increases the voltage of the battery, while wiring cells in parallel increases the ampere-hours.  Here is a simplified diagram of the large capacity (10.8 volts, 7800 mAh) battery that I use in my Toshiba laptop:

The design of this battery has three "sticks" of cells.  Each stick of three cells produces a voltage of 10.8 volts, assuming that the cells in the stick have a capacity of 2600 mAh at 3.6 volts.  By wiring three sticks in parallel, the battery capacity increases to 7800 mAh.  The ELC calculation for a single cell is:

2.6 x .3 = .78 grams ELC

The difficulty comes when you try to calculate the ELC for the battery.  Toshiba's advertising states that this is a 9 cell battery.  If you started with the mAh rating printed on the battery, and then multiplied that by the number of cells, you'd get:

7.8 x .3 x 9 = 21.06 grams ELC

But that answer is incorrect.  Since the individual cells in the battery each have a capacity of 2600 mAh and there are nine of them, the correct calculation is:

2.6 x .3 x 9 = 7.02 grams ELC

This particular Toshiba battery, though considered high capacity, is below DOT's 8 gram ELC threshold.  The other Toshiba battery I have for the same computer is labeled 10.8 volts at 5200 mAh.  Toshiba states that this is a six-cell battery.  The ELC for that battery should be 4.68 grams ELC.  The battery in my company-issued laptop is rated at 10.8V/14.4V at 5.2 Ah.  I have no idea how many cells there are, or how they are arranged, but my assumption is that this battery would also be below the 8 gram ELC threshold.  If in doubt, check with the manufacturer.


Other Safety Considerations

Outside the regulatory compliance issues above, one subject touched on by the DOT web site regards overall lithium battery safety.  Damaged batteries, recalled batteries, and some batteries produced by third parties should not be carried on passenger aircraft.  With regard to third party batteries, this is more serious than it might appear.  Counterfeit batteries, and batteries that are very poorly designed and manufactured, are available online and through sites such as eBay.  A large number of the "name brand" lithium batteries offered on eBay are counterfeit -- just as are about 90% of the memory cards.  In either case, you should buy only from reputable merchants when using online auctions -- and that usually means from a brick-and-mortar vendor that uses the online auction for a web presence.

The issue takes on importance because in some parts of the world, manufacturer's batteries are very expensive and consumers are looking for better prices. (in the U.S.) sells the Olympus BLM-1 battery for $46.99.  The same battery on (Great Britain) sells for £43.56 -- that's $86.06 in U.S. funds at the exchange rate when I wrote this paragraph.

An interesting site to visit is one in the UK that tested several batteries marketed to replace the Olympus BLM-1 battery.  Many of the batteries have been disassembled so you can see what really goes into one.  Also, you can see that some batteries are not designed as well, and may not offer the same level of protection from overheating and other events.  And some are just plain shoddy or dangerous, as well as displaying false information on the label.  If you read through the site you will find that there are some aftermarket (third party) batteries that are made to the same standards as the original manufacturer's, but the average consumer may find it difficult to determine that out in the marketplace.

Testing and compliance for lithium-ion batteries will be an issue in the future.


What I Haven't Covered...

This page only deals with rechargeable lithium-ion batteries.  Also in the new regulations were restrictions on lithium metal batteries.  These are non-rechargeable or primary batteries, such as the CR123A cells that are used in some electronic flash units and LED flashlights, the CR-V3 batteries used in some cameras and flash units, etc.

That said, Panasonics product information indicates that with the new rules in effect, no more than three CR123A cells can be packaged together for transport/sale.  (CR123A cells have a capacity of 1300 mAh at 3 volts.)  In practical terms that allows up to three cells to be "packaged" together in your carry-on, allows them to be installed in some of the high end one- or two-cell LED flashlights, and allows them to be installed into adapters such as the Olympus LBH-1.

The LBH-1 mounts three CR123A cells and can be used in several of their cameras instead of their standard rechargeable lithium-ion battery.  Arguably, this also turns the LBH-1 into a "battery".

(I may get into more detail in the future, but I felt that the lithium-ion topic needed to be covered first.)


Information from the Regulations

Here are some definitions from the recent changes to 49 CFR Parts 171, 172, 173, & 175:

§ 171.8 Definitions and abbreviations.

Aggregate lithium content means the sum of the grams of lithium content or equivalent lithium content contained by the cells comprising a battery.

Equivalent lithium content ["ELC" - ed.] means, for a lithium-ion cell, the product of the rated capacity, in ampere-hours, of a lithium-ion cell times 0.3, with the result expressed in grams.  The equivalent lithium content of a battery equals the sum of the grams of equivalent lithium content contained in the component cells of the battery.

Lithium content means the mass of lithium in the anode of a lithium metal or lithium alloy cell. The lithium content of a battery equals the sum of the grams of lithium content contained in the component cells of the battery.  For a lithium-ion cell see the definition for ‘‘equivalent lithium content’’.

This table defines the sizes of the cells and batteries discussed in the regulations:

Battery and Cell Category Definitions

(no more than)
(more than)
     Primary 1g Li. 1g & 5g Li. 5g Li.
     Secondary 1.5 g ELC 1.5 g & 5 g ELC 5g ELC
     Primary 2g Li. 2g & 25g Li 25g Li.
     Secondary 8g ELC 8g & 25g ELC 25g ELC

Remember that batteries are made up of one or more cells.  Also, "Primary" refers to non-rechargeable cells and batteries, while "Secondary" refers to rechargeable cells and batteries.



Here are some links to information on this topic:

DOT's site announcing the new lithium battery policy.

DOT Pipeline and Hazardous Materials Safety Administration (PHMSA) news release of December 28, 2007

TSA's site announcing the new lithium battery policy.

PDF file of Federal Register with the Final Rule.

Copyright 2008 by Eshom Creek LLC.  No warranty or claim is made as to the accuracy or suitability of the information presented.  Individuals and entities are wholly responsible for their own compliance with federal safety and security regulations.