Before asking if it is safe to leave your smartphones or mobile devices charging overnight – it is key to understand how modern smartphone batteries work, and what are the best methods to conserve battery life.
How do Smartphone batteries work?
Whenever a person exhausts their device’s battery life from 100% to 0% – this is known as a full cycle, if the device is then recharged to 50% – this is a half cycle.
Device batteries usually begin to degrade after around 400 full cycles, usually happening after one and a half years of continuous usage of a smartphone.
Leaving your device plugged in and the battery at 100% all the time would not affect the battery’s charge cycle, actually using the device will.
Rechargeable batteries slowly lose capacity over time, even if they aren’t used. For smartphones, you may notice a capacity drop after the first year of use. After two years you may not be able to get a full day of use with a single overnight charge.
The fastest way to degrade your device’s battery is to regularly charge it past 80% (leaving it to charge overnight, for example) and letting it drop to around 20% before recharging. In fact, most manufacturers have informed users that to maintain the longest possible battery life on a smartphone, try to keep your phone above 20% and below 80% – which translates to almost 3 years of daily charges.
Is it Alright to Leave your Smartphone Charging Overnight?
Yes – but in the broader sense. Modern smartphones have safeguards installed to prevent the overcharging of batteries. Manufacturers have made devices smarter so that newer devices have in-built chips that will prevent charging once 100% capacity has been reached.
This safeguard feature is usually known as ‘trickle charge’ – where most devices will do one of two things. Either, stop charging when they reach 100%, or when the device reaches 80%, it will slow charge until you wake up.
The latest-model iPhones have a feature that learns when a user wakes up and goes to bed, making sure that overnight charging is spaced out so that around the time when a user normally wakes up is when the device finally reaches 100% charge.
However, prolonged charging does lead to increased temperatures, which does degrade batteries, and in very rare conditions, may lead to safety hazards – especially if the device is charged close to where you lay your head down at night.
To mitigate these risks, users could consider charging mostly during the day, when they’re awake, especially if they have older devices that have been giving battery issues for some time.
Newer devices are significantly safer, so users with these should really have no problems with overnight charging.