More and more travelers are finding the benefits of carrying extra rechargeable battery packs to power their array of devices. Airlines are relaxing their rules about usage of phones and tables while flying further increasing the need for battery power.
However, there is a lot of confusion about flying with batteries. Right now, the rule of thumb is that you can bring extra batteries with you with your carry-on luggage but you can not check-in spare batteries. The reason for this is that the main formulations for today's rechargeable batteries primarily consist of lithium-ion or lithium-polymer. The contents of these batteries are indeed flammable and could start a fire or even explode. This is incredibly rare but theoretically could happen. If something were to happen with carry-on luggage, there are people to extinguish the fire. Unlike the cargo area which is unattended. Because a fire is highly unlikely, batteries are allowed in carry-on. If the risk were greater, then they would be ruled out entirely. There are several battery developments in the works that address this specific issue but that is a topic for another article.
So if you have spare batteries, don't check them in but rather put them in your carry-on bag. To give you more specifics, the FAA has very specific guidelines. Regular alkaline batteries and dry rechargeable batteries (NiMH, NiCad) are allowed on both carry on and check-in luggage. You are still required to have batteries protected from shorting at all times (i.e. don't put open batteries in with a bag of paperclips).
For lithium-ion and lithium polymer, the FAA has different rules for different size batteries. For small/medium batteries with a maximum of 100 Wh (watt hours) you are allowed to carry on these batteries. The FAA does not specify how many batteries you are allowed to carry on but does state that multiple batteries are allowed as long as they are not over 100 Wh each. They use a subjective measure of "personal use" to define the quantity. So basically, 2-5 is probably okay but 50 batteries would not be ok.
Most larger batteries today will indicate the capacity in both mAh and Wh. To calculate Wh, from mAh, you simply take Volts x mAh / 1000. To give you an example, a typical battery bank is 5,000 mAh and 5V. So 5V x 5,000mAh / 1000 = 25Wh. A 20,000 mAh battery pack would equal 100Wh which is the FAA limit. A typical laptop battery is 11V and 4000 mAh so that would be 44Wh. So the spare laptop battery outside of a laptop could be carryied on but not checked-in. But the same battery inside a laptop could be checked-in as well.
Checking in these 100 Wh batteries is another matter. If these are pure batteries, like external battery packs, spare laptop battery, etc. they are not allowed to be checked-in. However, if they are installed inside equipment, then you can check the equipment in. The theory is that batteries installed inside equipment are much less prone to accidental fire hazard. Batteries larger than 100Wh is very rare.
The FAA regulations for larger size 100-160Wh batteries are actually identical to smaller size batteries with the exception that you are only allowed two per passenger. It is unclear whether you could have two on carry-on and two with check-in (only if in equipment). But they do state "per passenger" so to be safe, limit these ultra large batteries to just two total.
If you are interested in even more detail, here is a reference document provided by the FAA.
So there you have it. If you are carrying spare batteries, it is best to check them in. But if they are in equipment, you can actually check them in. Keep in mind, these are FAA guidelines and airlines may have stricter rules. Most airlines that we checked with simply mirror the FAA guidelines but sometimes customer service can be fuzzy on the regulations.
Here are some policy guidelines from various airlines:
United: Personal devices installed with a lithium ion battery of less than 100 watt hours are permitted in carry-on and checked baggage. Loose lithium and lithium ion batteries are not permitted in checked baggage on any United flight. In most cases, up to two larger lithium batteries (more than 100 watt hours, but not exceeding 160 watt hours) are permitted in carry-on baggage if the terminals are covered or insulated.
American Airlines: You can travel with spare lithium, lithium-ion batteries for devices such as laptops, cell phones and cameras as carry-on as long as the terminals are covered or insulated. You cannot travel with them as checked baggage. [VoltNow Note: They specifically reference spare batteries and do not mention in-equipment. They link to this site for detail which is consistent with FAA]
Delta: Passengers are permitted to travel with lithium ion batteries that contain a maximum of 160 watt hours per battery. Any lithium ion battery containing more than 160 watt hours is prohibited from carriage on all passenger aircraft. Lithium ion batteries installed in a personal electronic device can be transported as checked or carry on baggage. Lithium ion batteries not installed in a device (spares) must be in carry-on baggage and no more than two (2) spares between 100 and 160 watt hours are allowed.
Cathay Pacific: Same guidelines as FAA. Interestingly, they specify a maximum of 20 batteries carry-on limit under 100Wh each.
Another interesting aspect is related to batteries installed in equipment. Something like a smartphone (even with a user replaceable battery) clearly is a battery installed inside equipment. However, a product like our RiverFi Battery Speaker starts to blur the lines.
This is a 5200 mAh / 26Wh battery with an included speaker. So technically, it is a battery installed in a speaker. When we asked TSA and someone at an American Airlines counter, we were told it was fine to check in but we called it a speaker with a rechargeable battery. Our results might have been different if we called it a battery with speaker :)