Is it bad—or even dangerous—to leave a smartphone plugged in as you sleep? The answer is complicated, as are many things regarding batteries.
Lithium-ion batteries are being built to store more energy in a smaller space, and that combination is causing more danger of explosion, fire and injury. Lithium-ion batteries are rechargeable batteries that power cellphones, portable battery powered tools, laptop computers, toys and other electronic devices.
The emphasis here is placed more on batteries that are faulty. Hazards from faulty batteries include overheating, fire, electrical shock from battery chargers, thermal burns, exposure to alkaline battery electrolytes, and battery components being ejected at high velocities, according to the US Consumer Product Safety Commission (CPSC).
Trouble can occur while the battery is in use, in storage, or being charged, according to Consumer Product Safety Commission. A number of companies, such as hover board and cell phone producers, recalled products after widespread malfunctions.
Some manufacturers are developing less flammable solid-state batteries and other features that would improve safety, but progress is slow, and lithium-ion batteries are proliferating in the meantime.
Electronics makers continue to push for increasingly miniaturised, light-weight devices that use batteries with more energy packed into smaller spaces than in traditional rechargeable batteries.
The combination of “high-energy volatile chemistry packed into a small volume requires special safeguards to minimise potential hazards”, according to the CPSC website.
High-energy, high-density batteries need enhanced safety systems and additional care when they are in use, and they should be properly tested with the product performing its intended use and with its charger system, according to the CPSC and Underwriter’s Laboratory, Inc.
While test standards are in place for lithium-ion batteries, UL continues to revise standards and testing methods as new information about failures and their causes becomes available.
UL is especially focused on internal short circuit failures believed to occur during manufacturing. The problem is so small that workers don’t see the problem during manufacturing. Sometimes short circuit occurs later. Short circuit failures can lead to overheating, called thermal runaway, and can cause fires and injury.
“Although lithium-ion batteries have had some bad press with large notebook computer and cell phone battery recalls in the recent past,” Laurie Florence, UL principal engineer, wrote for the Society of Fire Protection Engineers, “the actual field failure rate compared to the number manufactured is extremely small, considering that over a billion lithium-ion batteries have been sold in the past decade.”
More than four million notebook computers were recalled in 2006. The fact that most people who use lithium-ion battery products on a daily basis never experience these types of incidents supports this assertion, “However, in the rare cases when an event leads to a thermal runaway, the results can be severe.”
UL recommends safety precautions including: reading product instructions and using lithium-ion powered products only as recommended; not overcharging batteries; and not over-discharging batteries.
The best thing to do: Don’t worry about this too much. Plug the phone in (or place on the wireless charger) when you go to sleep; if you wake up sometime in the night, unplug it/move it to prevent constant trickle-charging. If you don’t wake much, plug your phone into a smart plug that’s on a schedule so it turns off.
Potential problems that could be encountered while charging overnight:
1) It is hot in here? The trickle charge can cause some heating up. Many experts recommend taking a phone fully out of the case to charge overnight. At the very least, do NOT stack a bunch of crap like books or other devices on top of a charging device. And for the love of Jobs, don’t put it under your pillow. Do any of the above and you can expect the phone to get hot—not necessarily enough for spontaneous combustion, but at least enough to damage the battery (see below)
If you are afraid of fire, some people recommend leaving the charging device on a dish or saucer while plugged in, or putting it on something metal that is more likely to dissipate heat, like a heatsink does on the chips inside a PC. That’s not much of an option if you use a wireless charging pad, so don’t sweat it
2) Bad Cables. If you’re using a knock-off cable that isn’t from the manufacturer, or at least “certified” in some way (iPhone Lightning cables should be MFi certified, for example), it could be a problem. The cord and connectors may not be up to the specifications needed for the phone or tablet. Don’t skimp by buying chintzy cables.
“Don’t ever, I repeat, don’t ever let kids go to bed with their phones on the chargers,” Cellphones can overheat among flammable bed linens.
Also, stop using the battery if it emits an odour, changes colour, too hot, changes shape, leaks or makes odd noises, the National Fire Protection Association recommends. This is for your safety. Please share this article to your friends and family you want them to see this.