Don’t charge your smartphone overnight

Smartphone batteries can be temperamental things. They can fail at the most inopportune moments and can sometimes simply die unexpectedly when your phone says it still has hours of life remaining.

Opinion is often divided among consumers on the correct way to charge a mobile phone battery to ensure its reliability and continued effectiveness.

The myth that smartphone batteries need to be depleted before you should charge them again no longer applies, as lithium-ion batteries maintain their capacity much better than legacy technologies and are far more resilient to different charging habits.

One of the most common smartphone charging habits is probably leaving your device on charge throughout the night.

As our handsets are constantly at our side throughout the day, it stands to reason that the only opportunity many people find to charge their smartphone for an extended period of time is overnight.

There are a few perspectives on this charging habit, with many stating that you should refrain from charging your smartphone overnight if possible.

Leaving your phone plugged in

While leaving your smartphone plugged in overnight on your bedside table may seem to have little to no effect on your battery, many experts do not advise this.

Samsung has previously stated that charging your smartphone overnight is a bad idea, adding that leaving your smartphone connected to a charger when it is fully charged can lower battery life.

One of the consequences of overcharging a cobalt-blended lithium-ion battery (the variety found in modern smartphones) is that it can cause a plating of metallic lithium to form on the cells, compromising the battery’s safety.

Device manufacturers usually prevent overcharging by using their charging circuits to detect and stop the flow of electricity into the battery when it is fully charged.

It is better not to test this regulatory circuit, however, and users should try not to leave their devices on charge unnecessarily, Samsung said.

More importantly, said Samsung, users should only use the charger that came with their smartphone to prevent any unexpected damage.

Thermal runaway

Stories of tablets, smartphones, and laptops burning holes in furniture or otherwise damaging property are often related to faulty batteries or a phenomenon known as “thermal runaway“.

Far more than a description of how fire works, the term thermal runaway refers to a situation where an increase in temperature changes the conditions of a device in a way which causes a further increase in its temperature.

This reaction functions as uncontrolled positive feedback loop, with temperature building constantly and eventually escaping in a destructive result.

Speaking to The Guardian following a tablet-related fire incident, Staffordshire fire rescue’s Paul Shaw said that users should make sure they don’t charge their phones under pillows or on bedding, as this could cause thermal runaway.

“It’s called thermal runaway in the battery. It self-heats. It keeps going and going,” Shaw said. “A work surface or wooden side table are fine, because the battery won’t output enough heat.”

Other hotspots for inducing the process of thermal runaway in a smartphone battery include the hot dashboard of a car, and other covered and unusually warm areas.

Using cheap or uncertified chargers can also generate excess heat and in rare situations result in your phone catching alight, although this is usually preceded by a mechanical fault with the smartphone.

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Don’t charge your smartphone overnight