Why is charging your smartphone overnight harmful?

Battery performance degradation and potential dangers

The habit of charging your phone overnight may seem convenient but it has many potential risks, especially reducing battery life and causing safety hazards.

- Affects battery life:Your battery will degrade faster if you regularly charge it above 80% or let it drain below 20%. The ideal charge level to maintain the best performance of your battery is around 50%. Prolonged charging not only increases the temperature of your device, but also naturally shortens the battery's lifespan.

- Safety risks due to high temperatures:Charging your phone overnight or placing it under your pillow while it's charging is a dangerous habit. Lack of airflow can cause the battery to overheat, increasing the risk of fire or explosion.

Chargers and cables can also get hot, especially if you use non-genuine products. Cheap third-party chargers are cheap, but often unsafe and prone to problems.

- Impact of extreme temperatures:Phones and Li-ion batteries are very sensitive to temperature. Temperatures below 0°C or above 70°C can cause the battery to deteriorate quickly. Avoid leaving your phone in direct sunlight or in a car on very hot or very cold days, as this will significantly reduce the life of your device.

Overnight "trickle charging" reduces battery life

Your phone's battery can't be overcharged thanks to the protections manufacturers have built in. However, once the battery reaches 100%, the device will switch to "trickle charging," which means it provides small amounts of power to compensate for the phone's natural drain.

This means that if you constantly charge your phone and keep it plugged in, the battery will be overworked, constantly consuming energy unnecessarily. In the long run, this habit not only puts pressure on the battery but also reduces its lifespan.

Smartphones and tablets today typically use lithium-polymer batteries, a variant of Li-Ion batteries. These batteries are safer, more compact, and charge faster. However, the principles of longevity are similar to those of regular Li-ion batteries, as they operate on the same principle.

As you charge your battery, lithium ions move back and forth between the layers inside the battery cell. If you overcharge or let the battery run out, the integrity of the cell will be compromised. Cramming too many ions into the lithium layers not only increases the internal resistance, but also reduces the battery's performance and lifespan.

So what determines your phone's battery life? Manufacturers often rate battery life through the concept of "charge cycles." A cycle is when the battery is charged from 0% to 100% and then completely discharged back to 0%. The number of charge cycles given by the manufacturer indicates how many full charges the battery can handle before its capacity begins to degrade significantly.

To extend battery life, avoid extreme conditions. A full cycle can also be broken down, meaning if you charge from 20% to 80% multiple times, when added together, it will be equivalent to one cycle.

Maintaining a charge level between 20% and 80% not only keeps the battery running more reliably, but can also extend its life to 1,000 charge cycles or more, which equates to about 3 years of daily use before its capacity drops significantly.

How to take care of your smartphone battery

So how do you properly care for your smartphone battery? Many of us still have bad charging habits, like leaving it plugged in overnight. The good news is that adjusting these habits doesn’t have to be complicated or time-consuming, and a few small changes can help protect your battery and extend the life of your device.

- Reduce battery drain on your phone:

You can extend battery life by reducing charging frequency, because charging less often means fewer charge cycles, which helps your device's battery last longer.

Some simple ways to save battery include reducing screen timeout and lowering brightness, two factors that have the biggest impact on battery drain. Additionally, most smartphones have a built-in battery saving mode.

For example, the iPhone has a Low Power Mode that kicks in automatically when the battery level drops below 20%. These modes typically don’t have a noticeable impact on the user experience, and they also provide useful features like Screen Time on iOS, which not only lets you set up sleep schedules and app limits, but also helps you develop better device usage habits.

While many people think that Bluetooth and Wi-Fi drain a lot of battery, they actually don't have a huge impact. On the contrary, turning off GPS and mobile data can significantly reduce battery consumption, especially on modern devices.

- UseOptimized Battery Charging feature:

Companies often design phone batteries to not let you use their full capacity to protect the battery. However, the screen will still show 100% when the device reaches its maximum capacity limit.

To avoid charging your battery beyond the recommended 80%, the simplest way is to monitor the charging process. But obviously, this is not practical in everyday life.

Understanding that, Apple introduced Optimized Battery Charging in iOS 13. This smart feature automatically learns your charging habits. If you regularly leave your phone charging for long periods of time, such as overnight, the device will only charge to 80% and pause. Then, right before you need to use it, the phone will continue to charge to 100%, minimizing stress on the battery while still ensuring convenience for you.

You can turn this feature on or off by going to Settings > Battery > Battery Health & Charging > Optimized Battery Charging. Here, you'll also see information about your battery's Maximum Capacity compared to when it was new, making it easy to track battery degradation over time.

- Using the app while charging your phone will affect your phone's battery:

You should also avoid using your device for performance-intensive tasks while it's charging, although this is a common practice for many people. Regularly using your phone while it's charging can cause long-term, even irreversible damage to your battery.

Think of it like overclocking your computer's CPU: running too many applications at once will cause the device to heat up and performance to drop. It will also increase the frequency of "trickle charging," putting unnecessary stress on the battery.

It may be tempting to watch YouTube videos or play your favorite game while plugged in, but the price you pay is reduced battery life. This impact is especially noticeable if you plan on using your phone for long periods of time.

Not only does the habit of using heavy apps while charging reduce battery life, it also slows down the device significantly after about 2 years. So if you want to maintain the performance and longevity of your phone, avoid power-hungry activities while charging.

However, it's perfectly fine to quickly check your messages or emails while charging. Just make sure you're not doing anything performance-intensive like gaming or streaming video.

How to Extend Your Smartphone Battery Life

Here are some simple tips to help you extend your smartphone battery life:

- Use partial charge mode:Keep the battery at 20% to 80% instead of letting it fill to 100% or drain completely.

- Avoid overnight charging:Don't leave your phone charging overnight, as this is when the battery degrades the fastest.

- Keep the device at room temperature:Avoid exposure to extreme high or low temperatures, as extreme temperatures may damage the battery.

- Turn off unnecessary services:Reduce power consumption by turning off Wi-Fi, Bluetooth, or services you're not using. Use battery saver mode to extend the life of your battery between charges.

You may not notice a noticeable difference at first, but when your phone lasts all day on a single charge, you'll feel the value of these habits.

Phan Van Hoa