Don't charge your phone overnight, warns battery expert

Stock image of iPhone being charged
Devices like phones shouldn't be left charged unattended overnight, an Auckland battery expert says. Photo credit: Getty Images

A recent e-scooter battery explosion is a reminder that batteries should be treated with respect, an Auckland battery expert says.

Late last month, a charging scooter battery exploded in a central Wellington apartment, leaving one person in a critical condition. The force from the explosion was enough to crack the glass and move furniture. In the US, the United States Federal Aviation Administration (FAA) has warned passengers not to fully charge devices and phones when taking them on flights due to increased fire risk.

Neither event is a surprise to Peter Simpson, director of Simpower Battery Specialists.

"When you work with batteries long enough, you develop a respect for them," he told Nights.

"Batteries store large amounts of energy in a very small space. And, if you're storing that kind of potential, it's got to go somewhere."

While any kind of battery can be problematic, the increasing prevalence of lithium ion batteries – used in everything from E-vehicles to phones and laptops – means it's come to the fore in recent years. People need to remember to take care with these batteries and be mindful of their power, Simpson says.

As a general rule, he doesn't leave any batteries charging overnight because "things can go wrong". That includes phones, iPads or tablet devices.

"You can have a component failure. You can have all sorts of things happen. Of course, if you're leaving something unattended overnight, it doesn't take long for it to develop and turn into fire.

"Particularly with lithium ion and things like that, you can get a phenomenon known as thermal runaway, which is where the cell hits a certain temperature. And at that particular temperature point, the cells around it go, and it can't be stopped. And so you get rupturing or fire of the case. In that case, the cell will continue to burn until it's finished."

When it comes to taking a fully charged device on a plane, Simpson says the rules are confusing.

"The shipping guidelines say that, if you're shipping lithium ion batteries under the UN certification or shipping code of UN3480, the battery must not be in a state of more than 30 percent of charge. And that's the goal on a cargo aircraft. So suddenly, we take them on a plane at 100 percent charge, but it's not okay to ship them 100 percent charge on a cargo aircraft.

"The latest sort of information I've seen suggests that, potentially when the battery's 100 percent fully charged, that the different pressure at altitude could potentially have an impact on the battery. But, invariably, often the devices are not fully charged anyways.

"I've travelled with my phone at 100 percent charge, as I'm sure most people have."

Sim says there are "plenty" of counterfeit batteries on sale here. He believes there should be more control over who sells lithium batteries so consumers know that what they're buying is safe. Internationally, e-commerce giants eBay and Amazon have banned the sale of 18 650s, a type of lithium ion cell, but no such restrictions exist in New Zealand.

"From what I've seen in the market, you can buy unprotected lithium ion cells from places such as TradeMe and Facebook marketplace, and so on and so forth. There's no sort of certification with that. There's no kind of quality control checks. It's just a suggestion that, yes, this is a genuine product."

How to keep batteries safe

Don't short the battery out: "Don't cause short circuits. Don't put the positive and negative together, because that's the quickest way to essentially short the battery and cause a fire."

Don't heat up the battery: "Think about yourself, you like to be at room temperature, the battery likes to be at room temperature. If it's getting increasingly hot for you, the battery doesn't like that and potentially you can cause a rupture or or fire again.

Don't abuse the battery: "Don't disassemble or deform them or treat them roughly. They can become deformed by the pressure or an impact, and that might cause the internal separator puncture and that can cause an internal short circuit."

Don't mix them up: "Don't mix different types of batteries together. That's another big no-no. That can cause big problems."

Don't overcharge the battery: "Always try to match the charger to the battery. Generally, as a rule you're best to use the original one because it was designed to charge that battery."