So why can’t I pack an e-cigarette in my checked luggage? This and other battery-related mysteries revealed

The Samsung Galaxy Note 7 phone is almost a distant memory, according to a news release Monday from Samsung, which said 85% of the devices had been replaced. But the confusion in the wake of the havoc caused by the little fire starters lingers because of the B word: battery. Just what can you take on a plane when it comes to battery-operated devices? And why or why not? Here are the rules and regulations and an important reminder about what can happen when rules go out the window.

About now, your eyes have glazed over and you are reaching for the Sports section. But trust me when I tell you that batteries are far more interesting than the Los Angeles Rams or UCLA football, and they probably have a bigger impact on your life.

To educate myself, I attended Battery University. OK, “attended� is loftier than it was, which involved firing up the laptop at the dining room table, going online and perusing a treasure-trove of info about batteries while swilling several cups of coffee and eating a cronut. Still, if my college classes had been a tenth as interesting as BU, I might have learned something in, say, music appreciation.

Here are some of the gems from Isidor Buchmann, the author of the Battery U content and the founder of Cadex, a Richmond, Canada, company that hosts Battery U and whose expertise includes batteries and electronics:

— The word “battery� derives from Old French that has to do with cannons, not electrochemical cells.

— Rechargeable batteries date to 1859.

— The lithium ion battery found in cellphones, laptops, cameras, power tools and more is the object of our consternation, not the alphabet batteries — double and triple A, hefty C and D and alien-like 9-volt or transistor.

Except for the Note 7 (banned on aircraft and on Amtrak), most of our portable electronic devices contain lithium ion batteries that you need not worry about. Mostly.

“Lithium batteries give … substantial life to your [electronic] devices,� said Peter Goelz, a former managing director of the National Transportation Safety Board and now a safety consultant. “Almost all phones have them.�

Our need for constant connectivity means we are constantly charging our phones or tablets. “The lithium [battery] has extended cellphone life, and consumers have benefited from it,� Goelz said.

They have also been frightened of those batteries and sometimes injured by them. Remember the catching-on-fire hoverboard? Airlines banned them and many manufacturers recalled them. (To see the Consumer Product Safety Commission lists of recalled hoverboards).

In June, the safety commission also reported that Sony and HP recalled lithium ion batteries used in several laptop and notebook models because of fire hazards.

And then there is the e-cigarette, which has a small lithium ion battery. The device must be placed in your carry-on, not checked luggage.

You also must be careful with spare lithium ion batteries lest they come into contact with, say, keys or coins that can short them, said John Bradshaw, marketing communications director for Cadex, making them a fire hazard.

Why carry-on? Because if there is a fire, Goelz said, it’s better that it’s in the cabin than in the belly of the plane at 35,000 feet.

How can you know for sure what’s allowed and what isn’t?

You can read the Federal Aviation Administration’s guide to what batteries are allowed in checked or carry-on luggage, the Transportation Security Administration’s blogpost on the topic and the Department of Transportation’s take on the topic and you’ll have pretty much all the battery info you’ll need for your travels.

Here’s the short version:

— Your electronic devices — Note 7, notwithstanding — are generally fine either in checked or carry-on luggage. (But you never want to pack anything in checked baggage that you value, which has nothing to do with the battery but does have to do with bags getting lost or pilfered.)

— You generally can take spare batteries for cameras or watches, but pack those in your carry-on if they are not in the device.

— If you have spare batteries for your e-cigarettes, Bradshaw said, it’s best to pack them in individual plastic bags and keep them away from metal objects.

— Dry alkaline and dry rechargeable batteries can be packed in carry-on or checked.

— Check with your airline to see whether you can take larger lithium ion batteries with you and in what form.

The most important thing to know? The standards aren’t consistent from place to place or country to country, which is why I came home from China with one less external battery charger than I left home with. (“External chargers are also considered to be a battery,� the FAA’s battery guide says.)

I had two battery chargers in my carry-on bag; security in the Shanghai airport took the smaller one. I didn’t argue. Nor did I argue when security at the Wenzhou airport asked to open my checked bag because they thought they saw batteries inside. (The “batteries� were a Swiss Army knife and a travel router, and they were left there.)

Bradshaw said being prepared for the unexpected is your best bet this holiday season or any time.

“Even though you’ve done your homework and figured out what the regulations are and you’re certain you can bring a spare battery, [you have] to actually be prepared for whoever it is you come into contact with who may have a different opinion and regulation� in mind, he said.

“There’s a lot of misinformation and uncertainty around the whole battery thing.�

You can always Tweet the TSA (@AskTSA) with questions about what you can and cannot bring and where to pack it. If you have an issue in a U.S. airport, request a supervisor.

No one is trying to punish you. Is this battery anxiety born of an overabundance of caution? Perhaps. But looking at some of the video of hoverboards, Galaxy Notes and laptops, perhaps not. Because smoking — cigarettes or electronic devices — is never good for you or your fellow passengers.

Have a travel dilemma? Write to [email protected]. We regret we cannot answer every inquiry.