Will charging your iPhone overnight damage it? Can a cheap charger break your devices? We quizzed an expert to answer the biggest myths around charging

a phone charging with the usb cable plugged in with a percentage showing on-screen

We've put some of the most commonly-held myths around charging your gadgets to the minds behind some of the best-selling chargers on the market

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Aaron Brown

By Aaron Brown


Published: 03/04/2024

- 11:20

Updated: 04/04/2024

- 10:48

Keeping your laptop plugged in all-day? You need to make a change

There's no shortage of myths around battery charging — Will charging your phone overnight ruin the battery? Should you stop using your while it charges? Are all charging cables built the same? Can cheaper chargers damage your gadgets? the list goes on.

We decided to get to the bottom of some of these myths, so we quizzed the minds at Anker. This Changsha-based brand is the biggest mobile charger brand in terms of retail sales in 2020, 2021, and 2022 — so they know what they're talking about. Our questions were answered by the teams that make Anker's chargers and cables.


And thankfully — you don't need to worry about ruining your iPhone by charging it overnight.

That's because most modern smartphones have a built-in safeguard to prevent damaging the battery when it's plugged into the wall for hours on end. Known as optimised battery charging, this prevents the battery from continuing to draw power after it's reached 100% and is available on Android, Samsung, and iPhone.

But what about fast charging?

Next-generation chargers can fully refill the lithium-ion cell inside your phone in under 30 minutes. In comparison, the 5W plug Apple used to ship with every iPhone (until it stopped bundling chargers to cut down on e-waste in October 2020) would take roughly 9 hours to charge a recent iPhone from 0-100%.

Thankfully, the operating system has built-in protections to prevent any damage. That makes sense as it'd be a pretty terrible look if the flashy new fast-charging feature that the manufacturer was shouting about when you upgraded to the latest model actually damaged the phone.

A spokesperson for Anker reassured us that modern smartphones will "intelligently manage charging by fast charging to 80%, then switching to trickle charging to take it to 100%". This is designed to avoid sustaining high heat levels, which can degrade the lithium-ion battery cell over time.

If you need to recharge your device as quickly as possible, should you avoid using it?

Anker tells us that doing anything on your device while it's charging will "most likely" impact the charging speeds. "When you're using your phone, the temperature will increase, and high temperatures will slow down the charging speed," we're told.

Another common battery myth — do you have to wait until your battery is completely depleted before you recharge? No, Anker tells us, there's no reason to hold off recharging your phone.

So, there's not a lot that can go awry if you have a relatively modern smartphone in your pocket, but what about a laptop? These devices can be a little trickier.

If you work on a laptop and leave it plugged into the mains the entire time, it can have a pretty terrible impact on the health of your battery, the team at Anker tells us. "Keeping your laptop plugged in continuously may affect its battery's health due to heat and constant high voltage," we're told.

What's the most important component when charging — the cable or the mains plug?

Anker tells us: "Put simply, both are important, but the output depends on the charger itself. If you buy a 5W charger, it will be slower than a 15W charger.

"Also, normal USB-C cables can only pass a maximum of 60W through them. If your device requires more power than this, you'll need to use a cable that allows more power to pass through it."

While many modern laptops now rely on USB-C to charge ...that doesn't mean you'll be able to use exactly the same cable that shipped in the box with your phone, tablet, or Kindle. As Anker points out, the cable itself could be limiting the charging speeds reaching your laptop.

Another common myth is that using a fast-charger will always speed up the charging process, even if your device doesn't specifically support fast-charging. It turns out this one is not true, Anker says.

"Both the device and charger need to support fast-charging. You should be able to find charging input speeds for your device, and then you can choose a charger that supports these speeds. For example, the maximum charging capacity for the iPhone 15 is around 20W. So, to get maximum efficiency and charging, you'll need a charger that outputs a similar amount," we're told.

And lastly, if you're looking to save money — is the charger an area where it's alright to scrimp and save, or is it dangerous to use a poor-quality charger? Can it damage your battery?

We're warned: "Yes, poor-quality chargers can't always charge at a stable rate, which may damage the battery."

If you're shopping for a replacement charger, this is one area where you really don't want to cut corners. Make sure you're buying from a reputable brand with decent online reviews.

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