Can I leave my phone plugged into the charger overnight?

Posted On: 31 Oct, 2017

Can I leave my phone plugged into the charger overnight?

There’s a very popular myth about how you shouldn’t leave your phone plugged in overnight, how the battery gets degraded because of “overcharging”. This may have been true in the past, but today’s phones, and their batteries, are a modern tech marvel. Phone batteries have evolved so much over the years, becoming smarter and easier to manage.

So can you leave your phone plugged in overnight? The short answer is – yes, yes you can. For those interested in the nitty-gritty details of smartphone batteries, I suggest you read on.

How lithium-ion batteries work

The batteries in your modern-day gadgets — from smartphones to laptops to your Bluetooth headphones are lithium-ion batteries, which have been around for more than 2 decades. So how do these lithium-ion batteries work? They store and release energy by moving electrons from one “end” of the battery to the other. These two battery “ends” are known as electrodes – one is called the anode and the other is called the cathode. There’s a bunch of material in between the electrodes called the “electrolyte”.

All lithium-ion batteries work in broadly the same way. When the battery is charging up, the positive electrode gives up some of its lithium ions, which move through the electrolyte to the negative electrode and remain there. The battery takes in and stores energy during this process.


When the battery is discharging (powering a device), the lithium ions move back across the electrolyte to the positive electrode, producing the energy that powers the battery.


What is a charge cycle?

A charge cycle is equivalent to a battery being fully drained, but this doesn’t mean it has to be from one charge. According to Apple: “You might use 75 percent of your battery’s capacity one day, then recharge it fully overnight. If you use 25 percent the next day, you will have discharged a total of 100 percent, and the two days will add up to one charge cycle.”


The lifetime of a normal battery is measured in cycles. They typically have between 300 and 500 full cycles before they reach 70 per cent of their original capacity, which is equivalent to a couple of years of use. Leaving your phone in the charger overnight, even when it’s fully charged, won’t affect how quickly your phone runs through its cycles, which are drained by simply using the phone.

So how does overcharging not affect battery life?

Even though batteries are still almost the same as they have been for past two decades, the devices that they power have become much, much smarter. Modern smartphones are designed to avoid taking in more current than is necessary to fully charge them. In other words, they know when to take it easy. They can stop charging when the battery has reached its full capacity and begin using the charger as its primary power source, allowing you to wake up to a fully-charged battery while your phone remains powered on through the night.


The exception is in very hot conditions. Heat causes degradation of lithium-ion batteries, reducing performance. Since charging a phone does heat it up slightly, combining this with hot temperatures (over 30-40 degrees Celsius) can damage it. Try to keep your phone in a relatively cool spot while charging it.

How can I preserve my phone’s battery?

There are a couple of things you can do to reduce the speed with which your phone’s battery discharges:

Try to avoid using fast charge every single time you charge your phone. Most fast or rapid charge systems cause the battery to become hot, which we now know is bad for your battery.

Wi-Fi and Bluetooth don’t drain nearly as much power as they used to. Keeping them on is not likely to drain a huge amount of battery, although if you really want to maximize efficiency, it helps slightly to turn them off.

Charge here and there whenever you can. Lithium-ion batteries don’t respond well to being charged all the way up and then run all the way down.

There probably will be naysayers who believe that overcharging is a bad idea, but the truth is, there’s nothing wrong with wanting to start your day with a full charge. We’re all going to end up buying a replacement battery, either for our smartphones or our laptops – so being obsessive about it will not save you from having to deal with getting a new one a few years from now.

Source – Android Authority, Telegraph, Sustainable Nano


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