What Causes Phone Batteries to Overheat? Understanding Thermal Runaway

Smartphones are used all day for calls, gaming, navigation, videos, and a variety of other activities. Most individuals charge their phones overnight or carry them in their pockets without much regard for battery safety. However, incidents involving phones overheating, swelling, or catching fire serve as a reminder that smartphone batteries can be problematic at times.

One of the main causes of such occurrences is a process known as thermal runaway. According to a blog post by the UK-based scientific research company Ossila, this occurs when a malfunction within a battery generates heat quicker than the battery can release it. This heat can set off further reactions, causing the temperature to climb rapidly. If the process continues, the battery may expand, emit gas, or catch fire.

Most smartphones have lithium-ion or lithium-polymer batteries. These batteries store a large amount of energy in a small space, making them ideal for portable devices. However, damage or overheating might make them unsafe.

What Is Thermal Runaway in a Smartphone Battery?

A smartphone battery comprises multiple internal layers, including a thin separator that keeps the positive and negative portions separate. If the separator gets damaged, the two sides may come into contact, resulting in an internal short circuit. This can cause a chain reaction. First, the short circuit generates heat. The heat then breaks down the components inside the battery, releasing gas. As the temperature rises, more heat is generated. Gas pressure can accumulate inside the battery, causing it to expand or explode. In some situations, the expelled gasses can catch fire.

What Causes a Phone Battery to Overheat or Catch Fire?

Smartphone batteries can fail for several reasons. Physical damage, such as dropping, bending or puncturing a phone, can damage the battery's internal layers and increase the risk of a short circuit. High temperatures, such as leaving a phone in direct sunlight or inside a hot car, can also affect battery safety. Using poor-quality chargers and cables without proper safety controls may lead to unstable power flow or overcharging. In some cases, manufacturing defects, including poorly fitted internal parts, can cause battery problems. Battery ageing is another factor, as older batteries naturally wear down over time, lose performance, swell or become more likely to develop internal faults.

Tips to Charge and Use Your Phone Safely

• A few simple habits can help reduce the chances of smartphone battery overheating:
• Use the original charger or a trusted charger from a reliable brand.
• Charge your phone on a hard, flat surface instead of under a pillow, blanket or mattress.
• Avoid leaving your phone in direct sunlight or inside a hot car.
• Remove thick phone cases during fast charging if they trap heat.
• Avoid playing demanding games or using GPS navigation while fast charging.

Warning Signs You Should Never Ignore

Stop using and charging your phone if you notice any unusual warning signs. Battery swelling, such as a bulging back panel or a screen that starts lifting, may indicate an internal battery problem. Unusual heat is another warning sign, especially if the phone becomes very hot even when you are not running demanding apps. You should also watch out for strange smells or sounds, such as a chemical odour, hissing or popping noises, as these may indicate a battery fault.

If your phone shows these warning signs, unplug it if it is safe to do so and keep it away from flammable materials. Do not press, puncture or try to repair a swollen battery yourself. Get the device checked by an authorised service centre and do not use it again until it has been inspected. Smartphone battery fires are uncommon, but basic charging habits and early attention to warning signs can help keep you and your device safer.

This article is based on information from Gadgets Now