There are limits that were introduced by the US Federal Aviation Administration .
Those have been used as well by numerous other airlines, for example Cathay Pacific .
They generally impose a limit on capacity per passenger and on top of this disallow checking them in, so you must take them into your hand luggage.
If a website lists grams of Lithium, use this formula ( source ): 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
There is additional information available from the TSA and the IATA .
Some more information here from Thailand, as of Jan 2015 (sorry, a bit shaky)L
Essentially, anything above 32'000 mAh is forbidden, below that and
above 20'000 mAh is limited to 2 per person, below that there are no limits, but all only in hand luggage.
travel.stackexchange.com/users/3778/uncovery
I've had two battery packs / power banks, and travelled to several countries with several airlines, taking them as carry on, without any problem...until...
Last year, I flew from Tokyo Haneda, via Beijing, China to Vancouver, Canada.
In Beijing, Chinese officials sent me to a security point, where several people including myself had our power banks taken off us, to our protest.
More on the situation here .
In the end, I believe - from what they told me, it was because it didn't indicate the amperage / capacity anywhere on the device.
Which seems pretty dumb to me for a reason - it's still a commercially made product (made in CHINA),
but yeah, they confiscated it.
I also saw signs in Taiwan stating that they had to be in carry-on, NOT checked luggage for some flights,
so yeah, you should be fine taking it in carry-on.
travel.stackexchange.com/users/101/Mark Mayo
There have been rules re carrying batteries for many years.
They may be found in (at least) IATA documentation and also a number of courier companies and most battery manufacturers have advice documents.
Removable batteries must be carried in carry-on luggage with the exception mentioned below.
Having batteries in carry=on makes sense - would you rather have a fire in a cargo hold or an overhead locker.
(Answer: No! :-)).
There is an upper limit to the amount of Lithium metal that may be carried.
Some manufacturers provide specific mass of Li per battery.
Otherwise they have a linear conversion between Watt hour of battery (Vbat x mAh.) and Li metal.
On one occasion I travelled with a laptop with large battery, + spare battery +
2nd laptop
+ maybe 6 x camera batteries (7V2 x ~= 1500 mah).
I was approaching but still under the Lithium metal limit.
China are a power unto themselves - they make up rules that others do not have.
Export rules for batteries via eg Fedex do not apply to hina battery exports.
Batches of batteries need a per batch test house certification that they meet certain standards.
This apparently excessive zeal is because people are willing to ship dangerous junk and misdeclare it.
Presumably the certified test houses have had it made very clear what will happen if they pass junk.
There are rules re battery carrying which vary somewhat.
Some systems allow carrying loose batteries with ends taped otherwise rendered"safe" from accidental shorting. .
Sealed lead acid batteries that are spill
proof(and not all are!)
must be carried in checked luggage with a formal label stating that they are exempt under IATA regulation xxx.
This actually works.
I have seen signs that luggage has been opened and the battery checked but not removed.
travel.stackexchange.com/users/3301/Russell McMahon
Assuming that your 10500 mA∙hr battery pack operates at 3.7 V, the energy capacity would be 3.8 V × 10500 mA∙hr ≈ 40 W∙hr.
( Lithium-ion cells typically operate between 3.2 V and 3.8 V.) By IATA guidelines , that would be well under the 100 W∙hr limit for lithium ion batteries.
The IATA guidelines list additional conditions to be met as well.
(They must be genuine, certified batteries, for personal use, in reasonable quantities.
If being carried as spares, they must be protected from short-circuiting.)
travel.stackexchange.com/users/1219/200_success
Mine with 20000 maH was taken by the officer in charge at Krabi's Airport.
According to them it is too big and they can't allowed me to carry it.
travel.stackexchange.com/users/37141/user37141
When flying, are you allowed to bring battery packs / power banks? I'd like to bring my ACC 10400mAh Power Bank on several flights.
Are battery packs allowed in hand luggage?
travel.stackexchange.com
<air-travel><airport-security><hand-luggage><batteries>
travel.stackexchange.com/questions/42411
travel.stackexchange.com/users/21774/user1073075
There are limits introduced by the FAA on the amount of lithium metal that may be carried, but this will be different in different countries. Your battery pack may be confiscated if it is considered too big. The regulations state that there is an upper limit to the amount of lithium metal that may be carried on a plane. However, passengers should be aware that China applies its own rules and, in Thailand, a 20000 maH battery was confiscated at Krabi airport.
There have been rules for a long time about carrying batteries on planes. The limits were introduced by the US Federal Aviation Administration. As a result there is an upper limit for the amount of lithium metal tha may be carried.  The rules for China are different from everywhere else. In Krabi, Thailand, a 20000 maH battery was confiscated on arrival.