Charging a phone seems simple, but the combination of high-capacity batteries, fast-charging standards and the sheer number of chargers in a home means safety deserves attention. The USB Power Delivery specification has transformed what a single cable can do, while official guidance from platform makers and safety agencies helps you avoid counterfeit products, overloaded outlets and travel mishaps. Understanding these basics lets you charge confidently without putting your devices, your home or yourself at risk.
What USB Power Delivery means for your phone charger
The USB Implementers Forum (USB-IF) describes USB Power Delivery (USB PD) as a specification that enables more flexible power delivery along with data over a single cable. According to the USB-IF, the USB PD Revision 3.1 specification, announced in 2021, allows up to 240 watts of power over a full-featured USB Type-C cable and connector. Before that update, USB PD was limited to 100 watts using a solution based on 20 volts and cables rated at 5 amps.
USB-IF documentation explains that the updated specification introduces new fixed voltages of 28 volts, 36 volts and 48 volts, which enable power levels of 140 watts, 180 watts and 240 watts respectively. An adjustable voltage supply mode lets the device being powered request intermediate voltages between 15 volts and the maximum available fixed voltage of the charger. This means a single charger can serve a wide range of gadgets, from a small pair of earbuds to a laptop, without forcing every device to accept the same power level.
The USB-IF also notes that power direction is no longer fixed. A product with power, whether it is a host or a peripheral, can provide power. This allows, for example, a monitor connected to wall power to charge a laptop while still displaying. Intelligent system-level management lets each peripheral take only the power it needs and request more when required. For consumers, this translates to fewer separate power bricks and a more streamlined setup. To benefit from these capabilities, however, both the charger and the cable must support the relevant USB PD revision. The USB-IF maintains a compliance program and an integrators list, and companies that use certified USB logos must have a trademark license agreement on file.
How to identify a safe charger
Apple’s support page on USB power adapters states that all Apple USB power adapters undergo rigorous safety and reliability checks and are designed to meet government safety standards around the world. The company notes that many countries, including the United States, have adopted standards such as IEC/UL 60950-1 or IEC 62368-1. Apple adapters are designed for use with power sources rated to provide 100 volts AC to 240 volts AC at 50 hertz to 60 hertz.
Apple’s guidance also addresses third-party chargers. The support page says you can use third-party cables and power adapters that are compliant with applicable country regulations and international and regional safety standards. It warns that other adapters might not meet applicable safety standards, and charging with such adapters could pose a risk of death or injury. The page lists the wattages of adapters that shipped with various iPad and iPhone models, including 20-watt, 18-watt, 12-watt, 10-watt and 5-watt versions, but emphasizes that any compliant adapter can be used.
The U.S. Consumer Product Safety Commission (CPSC) and the Electrical Safety Foundation International (ESFI) offer a broader safety message in their joint fact sheet on extension cords and power strips. They urge consumers to look for a certification label from an independent testing lab on the package and on the product itself, and to avoid counterfeit goods. This advice applies equally to USB chargers. A certification mark from a recognized lab indicates the charger has been evaluated to meet safety standards. When you are shopping for a replacement charger or cable, checking for that label is a quick way to filter out questionable products. For cable labels, see our guide to choosing charging cables. Our Gadget Buying Checklist walks through the logos and support details to look for on any accessory.
Power strip and extension cord safety
Even a certified charger can become a hazard if it is plugged into an overloaded or damaged power strip. The CPSC and ESFI fact sheet reports that there are about 2,000 residential fires each year associated with electric cords or plugs, resulting in roughly 60 deaths. These fires often start because of short circuits, too many products plugged into a cord, or damaged cords.
The agencies recommend using extension cords only when necessary and only on a temporary basis. They advise against overloading a cord or power strip. For appliances with three-prong plugs, they say to use only three-wire extension cords. Cracked or worn cords should be replaced. When using outdoor tools or appliances, only extension cords labeled for outdoor use should be used. These precautions help prevent overheating and arcing that can lead to a fire. If you are setting up a charging station with multiple devices, it is safer to spread the load across several outlets rather than daisy-chaining power strips.
Traveling with chargers and lithium batteries
The Federal Aviation Administration (FAA) PackSafe guidance on lithium batteries covers power banks, cell phone battery charging cases, and spare rechargeable and non-rechargeable lithium batteries. The FAA explains that all lithium ion batteries are capable of overheating and undergoing a process called thermal runaway, which can occur without warning if the battery is damaged, overheated, exposed to water, overcharged, or improperly packed. Flight crews are trained to recognize and respond to lithium battery fires in the cabin, and passengers should notify the crew immediately if a battery or device is overheating, expanding, smoking or burning.
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. When a carry-on bag is checked at the gate or planeside, all spare lithium batteries and power banks must be removed and kept with the passenger in the cabin. The battery terminals must be protected from short circuit by leaving batteries in retail packaging, covering terminals with tape, using a battery case or sleeve, or putting them snugly in a plastic bag or protective pouch.
The FAA sets size limits: lithium metal (non-rechargeable) batteries are limited to 2 grams of lithium content per battery, and lithium ion (rechargeable) batteries are limited to a rating of 100 watt hours (Wh) per battery. With airline approval, passengers may carry up to two spare larger lithium ion batteries (101 to 160 Wh) or lithium metal batteries (2 to 8 grams). There is no quantity limit for most smaller batteries as long as they are for personal use; batteries carried for sale or distribution are prohibited. The FAA notes that many airlines, both domestic and international, may have stricter quantity and watt-hour limits, so you should check with your air carrier before traveling. For more on choosing a power bank that fits within these limits, see our guide on How to Choose a Power Bank.
Damaged or recalled batteries and battery-powered devices that are likely to create sparks or generate a dangerous evolution of heat must not be carried aboard an aircraft unless the damaged or recalled battery has been removed or otherwise made safe. The FAA directs travelers to the Consumer Product Safety Commission, manufacturer or vendor website for recall information.
Frequently asked questions
Can I use any USB charger with my phone?
You can use any charger that complies with applicable safety standards, according to Apple’s support documentation. The USB-IF notes that USB Power Delivery is designed to coexist with standard USB Battery Charging implementations, so a compliant charger will negotiate the correct power level with your device. However, chargers that lack a certification label from an independent testing lab may not meet safety standards and could pose a risk. The CPSC and ESFI specifically warn against counterfeit goods and advise looking for that certification mark on the package and product.
What should I look for to avoid counterfeit chargers?
Check for a certification label from an independent testing lab on both the packaging and the charger itself. The CPSC and ESFI highlight this as a key step. Apple’s support page says that genuine Apple adapters are certified to meet standards such as IEC/UL 60950-1 or IEC 62368-1, and that third-party adapters should comply with applicable country regulations and international and regional safety standards. If a charger lacks any certification marks, it is safer to avoid it.
How do I safely travel with spare batteries and power banks?
The FAA requires spare lithium batteries and power banks to be packed in carry-on baggage only, with terminals protected from short circuit. Most lithium ion batteries are limited to 100 watt hours per battery, and you can carry up to two larger batteries (101 to 160 Wh) with airline approval. Always check with your airline, as they may have stricter rules. Damaged or recalled batteries must not be brought on board. If a battery overheats, expands or smokes during a flight, notify the flight crew immediately.
For more guidance on choosing and using phone chargers safely, visit our Phone Chargers category.
