Portable electronics have become everyday companions, from smartphones and tablets to wireless earbuds and handheld game consoles. Keeping them powered safely means understanding a few key rules about lithium batteries, charging adapters, and how to handle devices when you travel. The guidance that follows draws directly from aviation authorities, safety standards organizations, and platform support documentation, so you can make informed choices without guesswork.
Lithium battery risks and air travel rules
Lithium ion and lithium metal batteries power nearly all modern portable electronics. The Federal Aviation Administration (FAA) explains that these batteries can overheat and enter a condition called thermal runaway, which may happen without warning if a battery is damaged, overcharged, exposed to water, or improperly packed. Manufacturing defects can also trigger the reaction. Because flight crews are trained to handle lithium battery fires in the cabin, passengers should alert a crew member immediately if a device or battery becomes hot, swells, smokes, or burns.
When you fly, the rules for lithium batteries depend on whether the battery is installed in a device or carried as a spare. The FAA’s PackSafe guidance states that spare (uninstalled) lithium ion and lithium metal batteries, including power banks and cell phone battery charging cases, must be carried in carry-on baggage only. If a carry-on bag is checked at the gate or planeside, all spare lithium batteries and power banks must be removed and kept with you in the cabin. The Transportation Security Administration (TSA) echoes this on its page for lithium batteries with 100 watt hours or less in a device, noting that spare batteries must go in carry-on bags.
For batteries that are installed in a device such as a laptop, phone, or camera, the TSA allows them in both carry-on and checked bags, though checked bags carry a “Special Instructions” note. The FAA directs travelers to its separate entry for portable electronic devices containing batteries, which generally permits checked devices under certain conditions. Because airline policies can be stricter, the FAA advises checking with your air carrier before traveling.
Watt-hour and lithium content limits
The FAA sets clear size limits. Lithium ion (rechargeable) batteries are limited to a rating of 100 watt hours (Wh) per battery. Lithium metal (non-rechargeable) batteries are limited to 2 grams of lithium content per battery. These limits cover nearly all consumer batteries. With airline approval, passengers may also carry up to two spare larger lithium ion batteries rated between 101 and 160 Wh, or lithium metal batteries containing 2 to 8 grams of lithium. This exception typically applies to extended-life laptop batteries or professional audio/visual equipment. The FAA notes that newer lithium ion batteries often have the Wh rating printed on them. If not, you can calculate watt hours by multiplying the battery voltage by the amp hours (Ah).
Protecting batteries and handling recalls
The FAA requires that battery terminals be protected from short circuit. Acceptable methods include leaving batteries in their original retail packaging, covering terminals with tape, using a battery case or sleeve, or placing them snugly in a plastic bag or protective pouch. Damaged or recalled batteries, or devices that may spark or generate dangerous heat, must not be brought aboard an aircraft unless the battery has been removed or otherwise made safe. The FAA recommends visiting the Consumer Product Safety Commission website or the manufacturer’s site for recall information.
Charging safety and certified power adapters
Safe charging starts with the power adapter you plug into the wall. Apple’s support page on USB power adapters explains that its adapters are designed to meet government safety standards around the world, including IEC/UL 60950-1 and IEC 62368-1, which cover information technology and audio/video equipment. The page notes that you can use a Mac USB-C power adapter or third-party adapters that comply with applicable safety standards. However, it warns that other adapters might not meet those standards, and charging with them could pose a risk of death or injury.
The USB Implementers Forum (USB-IF) oversees the USB Power Delivery (USB PD) specification, which defines how power is negotiated between a charger and a device. USB-IF notes that USB PD enables intelligent and flexible system-level power management, allowing a device to request only the power it needs. Chargers that pass USB-IF compliance testing and appear on the Integrators List can carry the certified USB logos. Certification shows the product went through the USB-IF compliance program. When shopping for a charger or cable, look for the USB-IF certification mark as one indicator that the product has been evaluated against the specification. For more on what to look for in a charger, see our phone chargers guide.
Apple’s documentation also highlights that many recent iPhone and iPad models ship without a power adapter in the box, relying on existing adapters and cables. The company states that you can use either a USB-A to Lightning cable or a USB-C to Lightning cable with your iPhone, and that any of the adapters listed on its support page will work. This reinforces a broader point: a quality, standards-compliant adapter matters more than matching the brand of your device. Our compatibility guides can help you match chargers and cables to your gadgets.
Everyday safety practices
Beyond travel, a few habits can extend the life of your batteries and lower risk. The FAA lists overcharging among the conditions that can lead to thermal runaway, so follow your device maker’s charging guidance. Storing batteries in a cool, dry place and keeping them away from metal objects such as keys or coins prevents short circuits. If a battery looks swollen, feels unusually hot, or has visible damage, stop using it and follow local disposal or recycling guidelines. The FAA’s warning about damaged batteries applies on the ground as well: a compromised battery can fail without notice.
When you carry spare batteries in a bag, use the same terminal-protection methods recommended for air travel, such as tape or a dedicated case. This is especially important for loose cells and power banks. For more on selecting a power bank that meets airline rules, read our article on how to choose a power bank.
Charging cables also play a role in safety. A worn or frayed cable can cause inconsistent power delivery or short circuits. Pairing a certified adapter with a good-quality cable that supports the correct power profile helps maintain safe operation. Our charging cables section explains what to look for in a cable, including USB-C labeling.
Finally, remember that portable electronics are part of a larger ecosystem of everyday gadgets. Whether you are setting up a desk workspace or packing for a trip, consistent safety habits protect both your devices and your surroundings. Browse our everyday gadgets hub for broader tips on using and maintaining the tech you carry daily.
Frequently asked questions
Can I pack spare lithium batteries in checked luggage?
No. The FAA and TSA both require spare (uninstalled) lithium batteries, including power banks and battery charging cases, to be carried in carry-on baggage only. If a carry-on bag is gate-checked, you must remove the spare batteries and keep them with you in the cabin.
What does the watt-hour rating mean, and how do I find it?
The watt-hour (Wh) rating measures how much energy a battery stores. The FAA limits lithium ion batteries to 100 Wh per battery for most travel. Many newer batteries have the Wh number printed on the label. If yours does not, the FAA says you can calculate it by multiplying the battery’s voltage by its amp hours (Ah).
Are all USB chargers safe to use with my phone or tablet?
Not necessarily. Apple’s support page cautions that adapters which do not meet applicable safety standards could pose a risk. The USB-IF recommends using chargers that have passed compliance testing and carry the certified USB logo, because they follow the USB Power Delivery specification and negotiate power safely with your device. Sticking with adapters that display recognized safety certifications is a practical way to reduce risk.
For more guidance on portable electronics, visit our Portable Electronics section.
