Why Experts Worry About Fast Charging

It’s a little complicated

Key Takeaways

  • Some experts say fast charging can hurt your battery’s health in the long-term.
  • Overheating the battery and reducing its overall lifespan are problems often brought up with fast-charging tech.
  • While experts have concerns, many say there are ways to get around the problems fast charging can introduce.
Smartphone showing is has a 100% charged battery

veronka & cia / Getty Images

Experts say fast charging can be a nice feature, but it may ultimately lead to a shorter battery life, depending on the battery’s design.

While battery life has continued to remain around the same threshold for the past several years, new features that decrease the amount of time it takes to charge your phone have become staples in new devices. Fast-charging, aka rapid charging, often promises to charge up to 50% of a phone’s battery in a matter of minutes. Now, though, Xiaomi has revealed that it can fully charge a phone in eight minutes flat. That may seem great, but experts say shorter charging times could come at a cost.

"To support fast charging, cell developers typically have re-designed the cell with thinner electrodes, thicker current collectors, and electrolyte optimized for high rate," Harrold Rust, the CEO of lithium-ion battery developer Enovix told Lifewire in an email. 

"These redesigns, however, can result in a loss of energy density. The alternative, higher charging rates without these modifications typically lead to a reduction in cycle life. The same changes to the cell design can reduce or eliminate this reduced cycle life, but again at the expense of energy density."

Taking off Time

One of the biggest drawbacks to current smartphone batteries isn’t just how long they tend to last between charges, but also how long the battery, itself, will hold that charge. Every charging cycle—a complete charging of the battery to 100%—ticks away at the lifecycle of the battery, inevitably leading to less juice per charge and even, sometimes, the battery dying completely. 

The reason fast charging has become such a divisive technical issue is because of how it works. Obviously, when a phone (or any battery, for that matter) is charged, it receives electricity from the outlet, which is then transferred to the phone. But, when you start to install features like fast charge, you change how quickly the electricity is traveling into the phone. This can then result in increased heat being discharged from the battery as it works to soak up the electricity being pushed into it.

Heat, experts say, is the number one reason fast charge is such a worrying feature.

"Smartphone batteries are made with heat dissipating components to allow for cooling," Radu Vrabie, founder of Power Bank Expert, explained in an email. "A fast charger works on an increased voltage. On the other hand, the heat dissipation may not be commensurate to the rate of charging with the increased voltage. A fast charger may, therefore, place your smartphone at a higher risk of overheating in the long run." 

Because more heat is being filtered into the phone with the additional charge, you run the risk of causing long-term issues with the battery, which will reduce the number of charge cycles it can use.

Finding Solutions

While heat is a concern, there are ways around it. For one, some batteries are designed specifically to work with their fast-charging components. This means they’re built specifically to filter out the additional heat that’s created with the increased charging wattage, which ultimately takes away any risk of overheating, at least in the short-term.

Another solution, which Tim McGuire, CEO of phone repair company Mobile Klinik, recommends, is including a slow-charging option in all new devices. This would allow consumers to fully manage how they want to charge their batteries, as well as control when they utilize the fast-charging technology.

"A fast charger may therefore place your smartphone at a higher risk of overheating in the long run."

"The fast charging feature does reduce how long a battery lasts as users continue to use their phones," McGuire explained. "A simple solution for the overall battery life to last longer would be to integrate a slow charge option in all devices."

Of course, phone manufacturers like Xiaomi also say they’ve found solutions to the problems that may arise with fast charging. Reportedly, the HyperCharge tech it showcased recently will slowly ramp down how much wattage is pushed into the phone, ending in a gentle charge that helps to protect battery longevity.

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