This document summarizes aircraft travel guidelines for batteries:


It has two categories of lithium batteries:

  • 8 grams or "equivalent lithium content" per battery
  • 8-25 grams or "equivalent lithium content" per battery

Is there a formula or rule of thumb for determining the lithium content by weight of batteries?


1 Answer 1


Is there a formula or rule of thumb for determining the lithium content by weight of batteries?

Short: 8 grams / 100 Wh or ~= 0.75 grams per 18650 cell in a typical laptop battery.

Longer: Guidelines below, but YLMV -*

I have traveled on occasion "at about the maximum limit" when all the batteries I carried were added up. But, in around 50 legs of international travel, nobody has ever asked or checked.
[I had more trouble carrying boxes of 48 new NimH AA cells, as they are XRay dense and they attract extra attention from security.] Rules stipulate that batteries must be carried as carry on luggage and this does seem like a good idea.]

I have carried out this investigation for my own purposes some years ago, but Gargoyled to see what others say. I arrived at the same site as above BUT at a page where they answer your question (or purport to)

On this page Safetravel.dot.gov (that's their name) who you'd hope would know (but possibly don't) say:

  • Equivalent Lithium Content (ELC). ELC is a measure by which lithium ion batteries are classified. 8 grams of equivalent lithium content are equal to about 100 watt-hours. 25 grams of equivalent lithium content are equal to about 300 watt-hours.

  • You can arrive at the number of watt-hours your battery provides if you know how many milliamp hours and volts your battery provides: mAh/1000 x V = wh

  • Most lithium ion batteries marketed to consumers are below 100 watt-hours (8 grams ELC). If you are unsure of the watt-hour rating of your lithium ion battery, contact the manufacturer.

ie 100 Wh/8g = 12.5 Wh/g or 0.08g/Wh

A single 18650 call has a Ah capacity of 2 to say 2.5 Ah. Some claim higher but they are less believable (eg Everfire sell "3000 mAh" cells) and you also would rather they were wrong for this calculation.

On the above basis
a 3.6V nominal 2 Ah 18650 cell = 7.2 Wh =~ 0.6 gram
a 3.6V nominal 2.5 Ah 18650 cell = 9 Wh =~ 0.7 gram

To be easy and safe, say 0.75g/18650 cell

Laptop batteries tend to come in multiples of 3 or 4 cells.
Netbooks may have sub 18650 cells. Larger laptops tend to use 18650 cells.
Likely offerings are 18650 x
3, 4, 6, 8, 9, 12. giving
2.25, 3, 4.5, 6, 9 grams of Lithium per battery.

Happy the man (or woman) with a 12 cell laptop battery ! Even the 12 cell is so close to the limit that some refining of the calculations may show it falls below the threshold. It seems like this is aimed at laptop battery size or smaller, versus a larger than laptop division.

*-Your Lithium May Vary

MUCH more on web on this.

More later maybe ...

The following links are pertinent and may be useful.
Rushing out ...
I'll consider annotating them later:

Table good but does NOT relate to actual gross metal used

Applies 8g/100Wh simplistically.

Discussion. May be useful

Discussion. May be useful

Safe Travel again. Read !

Useful - citing safetravel site

  • \$\begingroup\$ The Safe Travel link now redirects to the site of the Pipeline and Hazardous Materials Safety Administration (PHMSA phmsa.dot.gov). It contains a page of definitions (phmsa.dot.gov/safetravel/definitions) that contains the same information. \$\endgroup\$
    – Bram
    Jun 21, 2015 at 8:50
  • \$\begingroup\$ This is inconsistent with your answer here, which (falsely) claims "A significant part of the weight in a LiIon battery is Lithium metal." A typical 18650 weighs about 45g, but above you claim it has about 0.75g Lithium content, hardly a significant part of its weight. Even if you mean the nebulous "equivalent Lithium content", whatever its definition, surely it is not meant to be more than an order of magnitude different from the actual Lithium metal content. \$\endgroup\$ Nov 23, 2015 at 22:48

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